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Benign schwannoma of the medial dorsal cutaneous nerve of the foot: A case report

Posted on July 31, 2020 | Comments Off on Benign schwannoma of the medial dorsal cutaneous nerve of the foot: A case report

by Mark Capuzzi DPM1, Zachery Weyandt DPM1, Dawn Masternick DPM2

The Foot and Ankle Online Journal 13 (2): 6

Schwannomas are benign soft tissue tumors of Schwann cells in the peripheral nerve system that can occur in the foot and ankle with preference for the posterior tibial nerve. A 60-year old female with a histologically diagnosed schwannoma of the medial dorsal cutaneous nerve is described in a location that is atypical according to the literature. These soft tissue masses can easily be misdiagnosed, and MRI studies can be inconclusive in determining possible malignancy. Clinicians should be suspicious and include malignant peripheral nerve tumors in their differential diagnosis with excisional biopsy as a way of definitive diagnosis.

Keywords: schwannoma, foot and ankle tumor, soft tissue mass, medial dorsal cutaneous nerve

ISSN 1941-6806
doi: 10.3827/faoj.2020.1302.0006

1 – University of Louisville Podiatric Medicine and Surgery Residency/Fellowship, Louisville, Kentucky
2 – Tipton and Unroe Foot and Ankle Care, Kentucky

* – Corresponding author: mjc5527@gmail.com

Neurilemoma was originally described histologically by Verocay in 1908, with the term schwannoma being coined by Abadie and Argaud some 20 years later [1]. Schwannomas are a variety of peripheral nerve sheath connective tissue masses that arise in the periphery usually of benign nature. This group also includes neurofibromas and malignant peripheral nerve sheath tumors (PNSTs) that are classified based on their histological appearance. Schwannomas are solitary encapsulated tumors histologically described by homogenous arrangement of palisading cells (Verocay bodies) and exhibit hypercellular and hypocellular areas of devoid spindle cells; otherwise known as Antoni A and Antoni B [2]. These lesions can have major clinical impact on the neurocutaneous diseases neurofibromatosis 1 and neurofibromatosis 2 or can be seen as isolated occurrences without systemic involvement [3].

In a retrospective single-center study by Toepher, et al., 25.2% of all foot and ankle tumors were reported to be benign soft tissue tumors, of which, 16 different variants exist. The most common of which are hemangiomas, pigmented villo-nodular synovitis, superficial fibromatosis, and schwannomas, respectively [4]. Neurinoma/schwannoma account for about 1-10% of all soft tissue tumors in the foot and ankle. It is estimated that 1% of cases have malignant potential [4].

Schwannomas are most frequently seen in the trunk, head, neck, retroperitoneum, brachial plexus, and posterior tibial nerve [5]. Multiple case studies have been published in recent years describing these tumors in the foot and ankle, usually in connection with the posterior tibial nerve, but less commonly also seen in areas of the digits and the forefoot [6,7,8,9].

In this detailed case report, we describe a 60-year old woman with a schwannoma of the medial dorsal cutaneous nerve. The palpable mass arises in the dorsal midfoot associated with the tarsometatarsal joint, an area that has only been reported once in the literature and extending distally over the 2nd metatarsal base. The report includes a thorough clinical history, physical examination, diagnostics, as well as a histopathological description.

Case Report

A 60-year old Caucasian female presented to the attending surgeon’s private clinic with a chief complaint of a painful right midfoot mass that began one year previous. She felt the lesion had been increasing in size over time and worsening in severity of pain. She recalls the pain began only in shoe wear, as a rubbing irritation, but upon presenting to the clinic was painful also while walking barefoot. The patient’s history revealed trauma to the area of the mass two years ago when a large sign was dropped on her foot that she did not seek medical care for, leaving her foot bruised. She denied any other source of pain and other cutaneous masses as well as any history of puncture wounds or foreign bodies. Her medical history includes tubular adenoma, hemorrhoids, osteopenia, and a non-descript heart murmur. She denied taking any prescription medications, using only calcium supplements daily for her osteopenia.

Clinical examination revealed an apparently healthy female in no acute distress. A family history was non-contributory for soft tissue masses and a review of systems was unremarkable. Vascular examination revealed palpable pedal pulses and a brisk capillary refill time to all digits. Neurological examination revealed normal sensory sensations to digits and foot without deficit. No Tinel’s or Valleix’s signs were noted. Biomechanical examination revealed pes planus foot type with normal range of motion of all joints and without structural deformities. Dermatological examination revealed an oval, mobile, semi-compressible, tender to palpation, subcutaneous mass beginning over the 2nd tarsometatarsal joint extending over the base of the 2nd metatarsal. The bulk of the mass was distal to the 2nd tarsometatarsal joint. The mass was non-adherent to underlying structures without signs of infection, drainage, or irritation. There was no open wound in the area or bony exostosis. The mass measured 1.0cm x 1.0cm. The mass did not transilluminate nor have a palpable pulse.

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Figure 1 T1 Sagittal and T2 Axial MRI.

Differential diagnoses discussed included: fibroma, neuroma, neurofibroma, lipoma, foreign body, and benign/malignant peripheral nerve sheath tumors. The patient was educated and was presented treatment options for a ganglion cyst during her first appointment. She agreed to receive a corticosteroid injection in the area of the mass. She returned one month later without improvement and received a second injection, with aspiration attempted, revealing no fluid collection. At the 3rd visit, the patient again demonstrated no signs of improvement and worsening pain. An MRI was ordered at this time as there was a lowered clinical suspicion for a ganglion cyst (Figure 1).

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Figure 2 Schwannoma immediately visible in superficial fascia after incision.

The impression of the MRI report read a 6mm x 6mm x 4mm subcutaneous nodular lesion, superficial tear contacting the second extensor tendon anterior to the second TMT joint.

The radiologist suggested statistically the mass was a synovial/ganglion cyst but could not confirm or deny a benign or malignant soft tissue mass on a non-contrast MRI. The patient was educated on the results of her MRI and the inconclusive results. Upon discussion of an additional attempted aspiration versus further work-up including a MRI with contrast, a MRI with contrast was ordered. The second MRI reported a fairly uniform enhancement of the previously noted well-circumscribed subcutaneous nodular lesion along the dorsal aspect of the midfoot. The enhancement aspect of the image favored a non-cystic benign or malignant soft tissue mass in which surgical excision was recommended. Surgical excision was proposed and agreed upon by the patient.

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Figure 3 Schwannoma after surgical dissection with distal nerve continuation.

She was taken to the operative room and monitored anesthesia care was exercised in addition to a V-block of local anesthetic just proximal to the soft tissue mass. An approximately 3cm longitudinal incision was made directly over the mass. Careful and meticulous dissection immediately revealed a yellow, firm, and oval mass in the subcutaneous tissue that was encapsulated (Figure 2). The mass was freed from its surrounding structures with ease. Upon further blunt dissection, nerve-like structures were found to be projecting from the mass in a proximal and distal direction with abnormal thickening. The nerve-like projections mimicked the course of the medial dorsal cutaneous nerve as it extends to the 2nd interspace (Figure 3). A measurement of 5mm proximal and distal to the mass was marked and the nerve was transected and removed from the body in its entirety. The specimen was placed in formalin and prepared for histopathological examination (Figure 4).

Figure 4 Pathological specimen of schwannoma without distal and proximal nerve projections.

Upon visual inspection, no further remnants of the mass or abnormal nerve remained and the area was irrigated. Deep structures were approximated with vicryl sutures and skin was closed with prolene. The patient was placed in a soft dressing to the operative foot.

The pathology report grossly described a soft tissue mass of the right foot received in formalin, as yellow-white soft and feathery tissue in multiple fragments. The pathologist described a low power photomicrograph showed a well-circumscribed and encapsulated nodule with no infiltrating borders and no identifiable necrosis. High power photomicrograph showed bland spindle cell proliferation with eosinophilic cytoplasm, indistinct cell borders, and tapered nuclei (Figures 5 and 6). Mitotic figures were inconspicuous. Immunohistochemical stain for S100 was strongly and diffusely positive in the neoplastic cells. Schwannoma was favored by palisading nuclei and encapsulation.

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Figure 5 H&E Histopathological image.

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Figure 6 S-100 stain positive.

Post-operative protocol for the patient included full weight-bearing as tolerated in a surgical shoe to the operative side. She was evaluated two weeks out from surgery, demonstrating a well healed surgical site without wound dehiscence, infection, or pain. Sutures were removed at this time and the patient returned to normal shoe gear. She was encouraged to complete range of motion exercises at this time. The patient’s follow up at 4 weeks again demonstrating a healed surgical wound in the absence of pain. The patient was satisfied with her surgical results. A phone call was conducted 6 months post-operatively, and the patient denied any pain, wound complications, no neurologic symptoms, and noted she was extremely satisfied with the result.

Discussion

The diagnosis of a Schwannoma, can pose a challenge for a clinician in the office setting. As reported, our patient was originally thought to present with a ganglion cyst which was treated with steroid injections and attempted aspiration. For any benign soft tissue mass, multiple differential diagnosis should be thought of prior to intervention, such as, but not limited to, ganglion cyst, fibroma, neuroma, neurofibroma, lipoma, and benign/malignant peripheral nerve sheath tumors. Good practice dictates that if the mass is not responding to conservative measures, biopsy with histopathological examination is the standard of care. Excisional biopsy is the accepted technique in cases of the foot and ankle with small lesions (< 2cm) located in the subcutaneous tissue as was the case in our report [10].

Schwannomas’ have been reported in the foot and ankle literature, however, rarely in the dorsal midfoot. To the author’s knowledge only one other case has been reported in the location of the tarsometatarsal joint [11]. An area not uncommon to find ganglion cysts corresponding to an underlying joint. Knight, et al., retrospectively review 234 benign solitary schwannomas and describe their peripheral nerve distribution. Of 64 schwannomas involving the lower limb and pelvis, they reported the most commonly involved nerves included the sciatic nerve (n = 15), tibial nerve (n = 21), and common peroneal nerve (n = 15) [12]. Kransdorf, et al., described one of the largest retrospective review studies regarding benign soft tissue lesions. They looked at over 18,000 benign soft tissue lesions, and further categorized them via distribution of specific diagnosis by age, sex and location. Regarding total body distribution, schwannoma prevalence in the foot and ankle was 0.09% (81/895). No definitive predilection for male vs. female has been noted in the literature. There is a wide age range, with the majority of patients being between the ages of 50-70 years old [13].

Topfer, et al., as part of a retrospective study looked at the data of patients that were treated for foot and ankle tumors between June 1997 and December 2015. The primary aim of the study was to describe the prevalence, demography, and anatomical distribution of the tumors. This study presented an analysis of the second largest population of patients, with current literature. Out of 7487 musculoskeletal tumors, 413 cases (5.52%) of tumors of the foot and ankle were included. There were 147 soft tissue tumors (36%), of those 104 (71%) were benign and 43 (29%) were malignant. Benign soft tissue tumors, including all variants, were most commonly located in the ankle and midfoot. Malignant soft tissue tumors were most commonly at the midfoot. Schwannomas specifically were most common in the hindfoot and least common in the midfoot. Of the 104 benign soft tissue tumors, only 11 were found to be Schwannomas with zero being found in the midfoot and only one in the forefoot [4]. Malignancy should be suspected early in treatment, with regard to the aforementioned literature at hand.

Hao, et al., conducted a literature review of schwannomas that included 46 reported masses. Of the 46 schwannomas, 14/46 were on the ankle, 14/46 plantar aspect of foot, 9/46 heel, 3/46 interdigital spaces, 1/46 dorsal foot over 4th and 5th metatarsal, 5/46 unreported anatomical location. Again, none were found associated with the tarsometatarsal joint or located in the midfoot [7].

Conclusion

To our knowledge this is the first reported case of a schwannoma associated with the dorsal 2nd tarsometatarsal joint, and one of two reported cases overlying the tarsometatarsal joint complex. They can be difficult to diagnose clinically and become more challenging when mimicking a common ganglion cyst location. A detailed medical history is to be performed on all patients, with a high index of suspicion in patients with a familial history or active history of Neurofibromatosis Type 1 or Type 2. Recurrence and failed attempts of injections and/or aspirations should warrant the podiatric physician to have a detailed discussion regarding surgical intervention. MRI can be an effective diagnostic and surgical planning tool; however, surgical excision and histopathological examination is considered to be the gold standard. Particularly in cases where MRI cannot definitively diagnose a mass and is inconclusive in regard to a mass’s malignancy.  Schwannomas may resemble other soft tissue tumors of the foot and diagnosis is generally made via histopathological findings status-post excision, as was the case in this report.

Funding Declaration: N/A

Conflict of Interest Declaration: No Conflicts of Interest to Report

Acknowledgements: University of Louisville Department of Pathology

References

  1. Spiegl, P. V., Cullivan, W. T., Reiman, H. M., & Johnson, K. A. (1986). Neurilemmoma of the Lower Extremity. Foot & Ankle, 6(4), 194–198.
  2. Carvajal JA, Cuartas E, Qadir R, Levi AD, Temple HT. Peripheral nerve sheath tumors of the foot and ankle. Foot & Ankle International. 2011;32(2):163-167.
  3. Ferner RE, O’Doherty MJ. Neurofibroma and schwannoma. Curr Opin Neurol. 2002;15(6):679–684.
  4. Toepfer A, Harrasser N, Recker M, et al. Distribution patterns of foot and ankle tumors: A university tumor institute experience. BMC cancer. 2018;18(1):735.
  5. Tladi MJ, Saragas NP, Ferrao PN, Strydom A. Schwannoma and neurofibroma of the posterior tibial nerve presenting as tarsal tunnel syndrome: Review of the literature with two case reports. Foot, The. 2017; 32:22-26.
  6. Daniel M, Waters D, Chen C, and Brouyette N. Posterior tibial nerve schwannoma in a multiple myeloma patient: A case report. SAGE Open Med Case Rep 2019; 7:2050313×19838441.
  7. Hao X, Levine D, Yim J, et al. Schwannoma of foot and ankle: Seven case reports and literature review. Anticancer research. 2019 Sep;39(9):5185-5194.
  8. Jabra, A. S., & Godoy, J. (2019). Rare Schwannoma Nerve Tumor in a Lesser Toe: A Case Report. Journal of the American Podiatric Medical Association, 109(4), 322–326.
  9. Merritt, G., 4th, Ramil, M., Oxios, A., & Rushing, C. (2019). Schwannoma of the plantarmedial aspect of the foot: A case report. Foot (Edinburgh, Scotland), 39, 85–87.
  10. Downey MS, Gredlein CM, eds. Chapter 92: Soft tissue masses. In, Southland J. T., Vickers D. F., Boberg J. S., Downey M. S., Aprajita N. and Rabjohn L. V., eds. McGlamry’s Comprehensive Textbook of Foot and Ankle Surgery, 4e ed. Lippincott Williams & Wilkins; 2013.
  11. Jacobson G, Edwards M. Neurilemoma presenting as a painless mass on the dorsal of the foot. Journal of the American Podiatric Medical Association. 1993;83(4):228-230.
  12. Knight DM, Birch R, Pringle J. Benign solitary schwannomas: a review of 234 cases. J Bone Joint Surg Br. 2007;89(3):382–387.
  13. Kransdorf MJ. Benign soft-tissue tumors in a large referral population: Distribution of specific diagnoses by age, sex, and location. American Journal of Roentgenology. 1995;164(2):395-402.

 

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Case study: Schwannoma of the tibial nerve in a patient with a history of neurofibromas

Posted on September 30, 2019 | Comments Off on Case study: Schwannoma of the tibial nerve in a patient with a history of neurofibromas

by Zachary T. Ritter, DPM, MS, FACFAS1*, Amy Kruger, DPM2

The Foot and Ankle Online Journal 12 (3): 6

A schwannoma is a common benign tumor of the peripheral nerve sheath.  Schwannomas are rarely found in the foot and typically do not elicit any painful symptoms. We report the case of a large schwannoma eliciting tarsal tunnel like symptoms in a patient with a previous history of neurofibromatosis within the spine. The patient had previously undergone lumbar laminectomy for neurofibromas of the lumbar spine that went on to develop pain in the right foot.  She then underwent extensive workup of this persistent right foot pain. She was treated for plantar fasciitis for several years, until presenting to our clinic. At that time, EMG findings showed tibial neuropathy and medial plantar nerve degeneration; accompanied by MRI findings consistent with a schwannoma of the tibial nerve. The patient underwent surgical excision of the mass. The pathology report revealed an encapsulated biphasic tumor composed of compact hypercellular areas and mixed hypocellular areas with foci of hyalinization with no malignant features measuring 3.7 x 2.5 x 2.0 cm, consistent with a diagnosis of schwannoma.  The patient had an uneventful postoperative course. At one year follow up, she was pain free but had persistent neuropathic changes to the distal forefoot. Currently, there are few reports in the literature of schwannomas arising the tibial nerve eliciting the symptoms of tarsal tunnel syndrome. The incidence of such a schwannoma in association of a patient with a history of neurofibromas is even more rare.

Keywords: neuroma, schwannoma, neurofibromatosis, plantar fasciitis

ISSN 1941-6806
doi: 10.3827/faoj.2018.1203.0006

1 – Chief of Podiatric Surgery. UPMC Susquehanna. Williamsport, PA.
2 – PGY-3. St. Luke’s University Hospital. Bethlehem, PA.
* – Corresponding author: ztritter@msn.com

A schwannoma is a benign soft tissue tumor of the peripheral nerve sheath. These slow-growing tumors can be difficult to distinguish from other benign tumors based on clinical findings [1]. The principal diagnosis is made histologically by by identifying the principle cellular elements—Schwann cells. This tumor was first described in the thorax [2], and is typically found in the head, neck, and flexor surfaces of the extremities [3]. The most common nerve affected is the eighth cranial nerve; however, the spinal roots as well as the sympathetic, vagus , ulnar, and peroneal nerves are commonly affected as well [3,4]. This tumor is rarely found in the tibial nerve in the region of the tarsal tunnel [5-9]. Finally it is highly uncommon to find this tumor in association with a neurofibroma, with only one report of a schwannoma of the posterior nerve accompanied by a neurofibroma in the tarsal tunnel itself [10]. There are currently no other reports of a patient with a schwannoma eliciting secondary tarsal tunnel syndrome in a patient with a history of symptomatic neurofibromas elsewhere in the literature.

We report a case of a large schwannoma of the tibial nerve located in the tarsal tunnel in a patient with a previous history of neurofibromas in the spine.

Case Report

A 69-year-old female presented to UPMC Susquehanna Foot and Ankle Clinic in July 2015 with right-sided plantar fascial pain accompanied by plantar foot numbness and tingling.  On clinical exam, her foot was neutrally positioned and demonstrated no clinically palpable abnormality. She did have a positive Tinel and Valleix sign. There was mild tenderness along the plantar fascial ligament origin. The patient had been treated by an outside physician for over 5 years with plantar fasciitis.  She had tried various conservative treatment methods including custom orthotics, physical therapy, and a series of corticosteroid injections, all of which provided only temporary relief. She additionally had a history of a prior lumbar laminectomy secondary to pain, after which she began to notice increasing right foot pain and paresthesias.  Her previous spine MRI (June 2014) revealed extramedullary enhancing masses and nerve sheath tumors leading to a diagnosis of neurofibromas.

During her first visit to our clinic in July 2015, an EMG from the previous month was reviewed.  On EMG, there was evidence of tibial neuropathy and degenerative changes of the medial plantar nerve leading to a diagnosis of tarsal tunnel syndrome.  After her first visit, the patient was recommended an additional course of physical therapy, given a script for new custom orthotics, and prescribed a nonsteroidal anti-inflammatory drug, meloxicam (Mobic). Following this course of treatment, the patient’s symptoms did not improve (Figure 1). An MRI was then ordered of the area which revealed a well-encapsulated oval lesion measuring 4.2 x 2.2 x 2.1 cm, appearing hypointense on T1 and hyperintense on T2 consistent with a diagnosis of schwannoma (Figure 2). 

At this point, surgical excision of the mass was recommended to the patient. An oncology referral was discussed, but deferred until after the procedure in the event that surgical pathology findings did not indicate malignancy. She underwent surgical excision of the mass and decompression of the tarsal tunnel in October 2015. 

Figure 1 Preoperative lateral weight bearing radiograph.

Figure 2 Preoperative MRI T1 and T2 images.

The patient was brought into the operating room and placed on the table in a supine position and general anesthesia was administered. Local anesthesia was then administered to the area utilizing a 1:1 mixture of 1% lidocaine plain and 0.5% bupivacaine plain.  A pneumatic calf tourniquet was applied and inflated.  

Attention was then directed to the medial hindfoot, where a curvilinear incision was made just posterior to the medial malleolus and extended to the medial aspect of the glabrous junction at the level of the porta pedis. The incision was then deepened over the tarsal canal. The flexor retinaculum was then identified and released. Extensive tortuous veins were noted within the tarsal tunnel and were gently mobilized. 

Figure 3 Intraoperative image of the soft tissue mass.

 

Figure 4 Intraoperative specimen of the soft tissue mass after removal from tarsal tunnel.

The tibial nerve was then identified and the proximal portion was mobilized. The dissection was then carried distally exposing a large, swollen tibial nerve just proximal to its bifurcation into the medial and lateral plantar nerves.  

A longitudinal incision was then made in the epineurium and the marginal nerve fibers were mobilized  and retracted in an extra capsular fashion. The tumor was then fully exposed. The plane of the tumor capsule was gently dissected from the epineural layers and the tumor was then separated without significant damage to the surrounding nerve fascicles, though there were several small fascicles noted to be entering the tumor at the distal and proximal poles (Figure 3). These fascicles were isolates in an effort to minimize nerve damage, but due to local ingrowth they were impossible to separate from the tumor and were transected.  

Once the tumor was completely removed, the area was thoroughly flushed with sterile saline solution.  The remaining tibial nerve at the level of the lesion was examined and found to demonstrate significant degenerative changes. As there was no obvious tissue to repair, an amniotic graft was then wrapped around the degenerative portion of the nerve in order to promote healing and prevent adhesions.

The incision was then closed in a layered fashion utilizing monocryl suture for the subcutaneous tissues and nylon suture for skin closure. The operative site was then infiltrated with an additional 10 cc of 1:1 mixture of 1% lidocaine plain 0.5% bupivacaine plain.   The incision was then dressed with xeroform and covered with a dry sterile dressing. A modified Jones compression dressing was then applied. The tourniquet was then deflated and a prompt hyperemic response was noted to all digits. 

The pathology report revealed an encapsulated biphasic tumor composed of compact hypercellular areas and mixed hypocellular areas with foci of hyalinization with no malignant features measuring 3.7 x 2.5 x 2.0 cm, consistent with a diagnosis of schwannoma (Figure 4).

The patient was permitted to immediately weight bear postoperatively in a surgical boot. At two weeks postoperative, she underwent suture removal and was transitioned to a street shoe as tolerated. She was followed until one year postoperatively, and found to have no functional limitations, but did continue to notice sensory changes in the plantar foot. 

Discussion

Schwannomas are benign, encapsulated peripheral nerve sheath tumors. They are commonly described throughout the literature by a variety of names: neurilemoma, neuroschwannoma, peripheral glioma, perifibroma, and schwannoma [11,12]. Typically these tumors are found elsewhere in the body (trunk, head, neck, upper extremities) and even more rarely in the lower extremities [2-3, 13].  The foot is noted only to be affected in approximately 10% of cases [3]. There are even fewer noted in the literature to be associated with the tibial nerve and eliciting tarsal tunnel syndromes [5-9].  

Neurofibromas are not typically found in with the foot and ankle.  In a study by Bakotic and Borkowski of primary soft tissue neoplasms of the foot, schwannomas and neurofibromas were noted to account for only 5.4% and 2.7% of all benign soft tissue tumors, and 2.0% and 1.0% of all total neoplasms respectively in the foot and ankle [14].  It is rarely reported to find these two types of tumors in association with one another, with only one report of a schwannoma associated with a neurofibroma in the tarsal tunnel [10]. 

There are currently no other reports of a patient with a schwannoma eliciting secondary tarsal tunnel syndrome and a history of spinal neurofibromas. Currently the recommended treatment for schwannomas of the foot and ankle is open surgical resection [15]. Fortunately, surgical resection has positive results with minimal morbidity and recurrence if resected entirely [16,17]. It is recommended to remove the lesion in total with great care not to damage the nerve through excessive violation of the nerve sheath or compromising the marginal neural fibers. 

We report a case of successful excision of a schwannoma of the tibial nerve located within the tarsal tunnel, eliciting symptoms leading to a diagnosis of tarsal tunnel secondary to tumor. The patient did have a significant medical history of painful neurofibromas of the lumbar spine confirmed on MRI with a subsequent lumbar laminectomy. While the patient did have EMG findings positive for tibial neuropathy and degeneration of the medial plantar nerve, we cannot effectively determine whether the patient’s symptoms were solely related to compression from the longstanding mass within the tarsal tunnel or if they were possibly exacerbated by the patient’s history of lumbar neurofibromas with subsequent surgical intervention. 

The patient’s postoperative course was uneventful.  She did regain some hindfoot and midfoot sensation, while completely eliminating her preoperative pain.  However, parasthesias persisted within the forefoot. 

References

  1. Graviet S, Sinclair G, Kajani N. Ancient schwannoma of the foot. J Foot Ankle Surg. 1995;34(1):46-50.
  2. Ackerman LV, Taylor FH. Neurogenous tumors within the thorax; a clinicopathological evaluation of forty-eight cases. Cancer. 1951;4(4):669-91.
  3. Odom RD, Overbeek TD, Murdoch DP, Hosch JC. Neurilemoma of the medial plantar nerve: a case report and literature review. J Foot Ankle Surg. 2001;40(2):105-9.
  4. Weiss S, Goldblum J, Folpe AL. Schwannoma. In: Enzinger and Weiss’s Soft Tissue Tumors, ed 5, Elsevier Mosby, Maryland Heights MO, 2008, pp. 853-862
  5. Hallahan K, Vinokur J, Demski S, Faulkner-jones B, Giurini J. Tarsal tunnel syndrome secondary to schwannoma of the posterior tibial nerve. J Foot Ankle Surg. 2014;53(1):79-82.
  6. Grossman MR, Mandracchia VJ, Urbas WM, Mandracchia DM. Neurilemmoma of the posterior tibial nerve with an uncommon case presentation. J Foot Surg. 1992;31(3):219-24.
  7. Mangrulkar VH, Brunetti VA, Gould ES, Howell N. Unusually large pedal schwannoma. J Foot Ankle Surg. 2007;46(5):398-402.
  8. Judd T, Jones T, Thornberry L. Schwannoma of the posterior tibial nerve: case study. J Am Podiatr Med Assoc. 2014;104(5):539-43.
  9. Nawabi DH, Sinisi M. Schwannoma of the posterior tibial nerve: the problem of delay in diagnosis. J Bone Joint Surg Br. 2007;89(6):814-6.
  10. Tladi MJ, Saragas NP, Ferrao PN, Strydom A. Schwannoma and neurofibroma of the posterior tibial nerve presenting as tarsal tunnel syndrome: review of the literature with two case reports. Foot (Edinb). 2017;32:22-26.
  11. White NB. Neurilemomas of the extremities. J Bone Joint Surg Am 49:1605-1610, 1967.
  12. Spiegel PV, Cullivan T, Reiman HM. Neurilemoma of the lower extremity. Foot Ankle 6:194-8, 1986.
  13. Jacobson JM, Felder JM, Pedroso F, Steinberg JS. Plexiform schwannoma of the foot: a review of the literature and case report. J Foot Ankle Surg. 2011;50(1):68-73.
  14. Bakotic BW, Borkowski P. Primary soft-tissue neoplasms of the foot: the clinicopathologic features of 401 cases. J Foot Ankle Surg. 2001;40(1):28-35.
  15. Kellner CP, Sussman E, Bar-david T, Winfree CJ. Schwannomas of the foot and ankle: a technical report. J Foot Ankle Surg. 2014;53(4):505-10.
  16. Carvajal JA, Cuartas E, Qadir R, Levi AD, Temple HT. Peripheral nerve sheath tumors of the foot and ankle. Foot Ankle Int. 2011;32(2):163-7.
  17. Kim DH, Ryu S, Tiel RL, Kline DG. Surgical management and results of 135 tibial nerve lesions at the Louisiana State University Health Sciences Center. Neurosurgery. 2003;53(5):1114-24.

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Giant conventional schwannoma of the foot: A case report

Posted on December 31, 2014 | Comments Off on Giant conventional schwannoma of the foot: A case report

by Low Chin Aun, MBBS; Agus Iwan Foead, MS Orthpdflrg

The Foot and Ankle Online Journal 7 (4): 3

Schwannomas, also known as neurilemmoma, are amongst the most common tumors arising from peripheral nerves. It usually presents as a solitary swelling and may occur anywhere in the body with a neural supply. However, its occurrence in the foot is rarely reported. We report a case of a sixty year old man with a large schwannoma of his right foot, who never sought treatment for 20 years since its first occurrence.

Key words: Schwannoma, neurilemmona, tumor, foot

ISSN 1941-6806
doi: 10.3827/faoj.2014.0704.0003

Address correspondence to: Low Chin Aun
Department of Orthopaedic Surgery, Hospital Tuanku Ampuan Najihah, Kuala Pilah, Malaysia.
robinlca@gmail.com

Schwannoma is the most common benign, neurogenic tumor arising from Schwann cells of nerve sheaths. It occurs most frequently in the head and neck region, especially involving cranial nerves and brachial plexus. It is seldom reported in the upper and lower limbs [1]. This tumor grows in variable size and usually present as a slow growing solitary tumor, rarely associated with pain and paraesthesia. Neurological symptoms often accompany larger swelling. Its occurrence in the foot is rarely reported. Schwannomas constituted 5% of all benign soft-tissue tumors, and only 9% of these schwannomas were found in the foot or ankle [2]. We report a case of a large cutaneous schwannoma of the foot and its management.

Case Report

A 60-year-old man presented to our orthopaedic outpatient clinic with complaints of a solitary swelling over the lateral aspect of his right forefoot. He claimed the swelling has been gradually increasing in size for the past twenty years and was associated with intermittent pain and paraesthesia at his right foot. The swelling prohibited him from wearing his footwear due to its size. Patient has tried traditional treatment with massage and ointments but had no improvement. His past medical history was unremarkable and there was no family history suggestive of neurofibromatosis.

Physical examination revealed a 10cm x 10cm x 8cm tumor over the lateral aspect of his right foot (Figure 1). Its consistency was firm, and it was attached to the underlying tissue. On percussion, it produces an electric shock similar to Tinel’s sign. However, there was no tenderness, erythematous, warmth or ulceration of the skin over the tumor. Neurovascular status of the right foot was normal. Systemic review was unremarkable. Plain radiograph of the right foot did not show any bony involvement (Figure 2).

 fig1

Figure 1 Swelling on the lateral aspect of patient’s foot.

fig2

Figure 2 X-rays revealing a tumor on the lateral aspect of patient’s right foot.

At surgical excision, the capsule was found at the deeper plane. There was no attachment of the tumor with adjacent soft tissue which permitted easy in toto removal. The wound was then closed with split skin graft harvested from his left thigh. The patient did not experience any complication postoperatively. The tumor was preserved in formalin solution and sent to the pathology lab. One month later he was reviewed again in the clinic. There were no evidence of recurrence and his wound had healed well with good uptake of the skin graft (Figure 3). Histopathological examination revealed a conventional right foot schwannoma with cystic degeneration.

fig3

Figure 3 Well healed wound post-removal of schwannoma.

Discussion

Schwannoma of the foot is interesting due to its rarity. Its diagnosis and treatment should be differentiated with neurofibroma or malignant peripheral nerve sheath tumor (MPNST). Schwannoma is embryologically derived from neuroectodermal Schwann cell which forms the myelin sheath that facilitates transmission of nerve impulses [3]. This well encapsulated tumor is usually benign in nature and malignant transformation is rarely reported [4]. Multiple schwannomas have been reported to have autosomal dominant inheritance. These tumors have also been associated with von Recklinghausen’s disease in which there is somatic mutation of NF2 gene. It appears that it has no geographical and race predilection. The average age of its presentation is 20 – 50 years with a mean age of 46 [2].

Benign peripheral nerve sheath tumors are divided into two major groups; Schwannoma and neurofibroma. Differentiation of schwannoma from neurofibroma is of importance because schwannoma can easily be shelled out without injuring the nerve contiguity. In neurofibroma, the nerve is incorporated into the mass. Surgery of neurofibroma might need to resect the nerve, and subsequent nerve grafting might be needed to restore function. Large schwannoma commonly undergo cystic degeneration. Few neurofibromas have cystic changes due to myxoid degeneration. There has been argument about the cystic degeneration between the two tumors. Most literature showed schwannoma has higher chance of cystic degeneration compared to neurofibroma. Histogenesis of schwannoma and neurofibroma has been argued for decades and is beyond the scope of the discussion. It suffices to say that solitary schwannoma is composed almost exclusively of cells with characteristics of differentiated Schwann cells. However neurofibroma shows the presence of three types of cells, i.e. Schwann-like cells, perineurial-like cells, and fibroblast-like cells. Histologically staining with S-100 shows that schwannoma has hypercellular area alternating with hypocellular area, which respectively are called Antoni A, and Antoni B areas. The hypercellular area is made up of spindle cells with tapered nuclei arranged in palisading pattern whereas the hypocellular area is composed of loose stroma [4].

Malignant peripheral nerve sheath tumor (MPNST) is a sarcoma which can originate from peripheral nerve or from the cell associated with the nerve sheath, such as Schwann cell, perineural cell, or fibroblast [5]. The term MPNST replaces previously used names including malignant schwannoma, neurofibrosarcoma and neurogenic sarcoma. Fifty percent of MPNST occurs in patient with NF1 gene. It typically occurs between the ages of 20 – 50. The clinical presentation is almost the same as schwannoma and neurofibroma except the rapidly enlarging mass within the time spectrum alerts the physician of the possibility of its malignant degeneration. Histological appearance shows dense cellular fascicles alternating with myxoid region. This swirling arrangement is also called marbleized pattern. The cells may be spindle, round or fusiform in shape. Nuclear palisading is very rare compare with schwannoma and occurs in only 10% of cases. Malignancy is suggested by invasion of the surrounding tissue, and vascular structures, nuclear pleomorphism, necrosis, and mitotic activity.

Conclusion

Schwannoma of the foot is a rare tumor which present as solitary swelling of the extremity. Clinicians should always consider schwannoma as a differential diagnosis during approach of mass in the upper or lower limbs. It is essential to differentiate schwannoma with neurofibroma, and also MPNST as each entity is differently managed clinically.

References

  1. Knight DMA, Birch R, Pringle J. Benign solitary schwannomas: a review of 234 cases. J Bone Joint Surg [Br] 2007;89-B:382-7. (PubMed)
  2. Kransdorf MJ. Benign soft-tissue tumors in a large referral population. ARJ Am J Roentgenol. 1995;164:395-402. (PubMed)
  3. Berlin SJ. Soft somatic tumors of the Foot: Diagnosis and surgical management. Futura Publishing Co, Mount Kisco, NY: 227, 1976.
  4. Harkin JC, Reed RJ. Tumors of the peripheral nervous system, fascicle 3, second series. Washington, DC: Armed Forces Institute of Pathology, 1969:60-64.
  5. Endo M,Yamamoto H, Harimaya K, Kohashi K, Ishii T, Setsu N et al. Conventional spindle cell-type malignant peripheral nerve sheath tumor arising in a sporadic schwannoma. Hum Pathol. 2013 Dec;44(12):2845-8. (PubMed)

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