Tag Archives: neurilemmona

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)

Schwannoma: A case report

by Mark J. Mendeszoon, DPM, FACFAS, FACFAOM1 , Natalie Cunningham, DPM2 , Robert S Crockett, DPM3 , Donald Kushner, DPM4

The Foot and Ankle Online Journal 2 (10): 4

Schwannomas are tumors derived from the myelin sheath of nerves. As schwannomas grow they can displace and compress nerves causing pain, weakness and numbness. Schwannomas usually exist as a solitary mass and can occur at random. Having no racial or sexual predilection, schwannomas usually occur in individuals between the ages of 20-50 years old. The most common sites for schwannomas are the head, flexor surfaces, upper extremity, lower extremity and trunk. It is very rare for schwannomas to become malignant, but surgery is still the principal treatment to eliminate symptoms that may persist and to correctly diagnosis the tumor. We discuss one case of a schwannoma found in the foot.

Key Words: Schwannoma, neurilemmona, peripheral nervous system tumors, Magnetic resonance imaging.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License.  It permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ©The Foot and Ankle Online Journal (www.faoj.org)

Accepted: September, 2009
Published: October, 2009

ISSN 1941-6806
doi: 10.3827/faoj.2009.0210.0004


Verocay was one of the first to describe a nerve tumor derived from the myelin sheath in 1908, termed neurinoma. [5] Later in 1935, Stout reported on tumors arising from the nerve sheath and specifically described tumors of neuroectodermal origin. [1 ]The neuroectoderm consist of Schwann cells and collagen fibers. [2] Schwannomas are tumors that arise from the myelin sheath of nerves and are the most common solitary nerve tumor of the body. [3]

Schwannomas can be found in various parts of the body with the most common site being the head. However, in the lower extremity they are most commonly found in the deep tissues of the foot. [10] Unlike neurofibromas, Schwannomas rarely metastasize. [4] As a schwannomas grows along the nerve sheath the fibers begin to push outward.

Studies relate a correlation between size of the nerve trunk and size of the lesion.[7] Lesions can be small or large, usually with a diameter less than 8cm when located in the foot. [11,12] Clinical evaluation of symptoms is sometimes a great indicator of what the lesion may be, but Magnetic Resonance Imaging (MRI) of the lesion is standard for obtaining differential diagnosis and determining the size and depth of the lesion. Once a lesion of this type is identified on MRI it must be surgically removed. The specimen is then sent to pathology, which allows the definitive diagnosis of Schwannoma.

Case Report

A 56 year-old female with a past medical history of hypertension, depression, and hypothyroidism first presented at age 54 with complaints of left foot pain and swelling of about one year duration. She related that she was bitten by a bug in the Caribbean and had swelling and discomfort since then. She denied any injury or trauma.

She also denied constitutional signs of infection. Initial radiographs failed to reveal any bony abnormalities or tumor like masses. The patient was then treated conservatively with an NSAID and change of shoe gear. A year later she returned complaining of an increase in the size of the left foot. She explained that her symptoms had never completely resolved and she noticed that her left foot was getting larger and more painful in her shoes which also were not fitting properly. An MRI was obtained which identified a large cystic lesion beneath the metatarsals extending from the cuboid to the metatarsophalangeal joints. (Figs.1 A – F) The lesion measured 8.0cm length, 2.8cm in depth and 3.1cm in width. The lesion coursed distally between the first and second metatarsals. Following the MRI the patient was scheduled for surgical removal of the mass in her left foot. (Figs.2 and 3) Initial histological report suggested neurofibromatosis but further analysis determined the lesion was a schwannoma with no evidence of sarcomatous transformation. The patient’s swelling was resolved within several weeks but she continued to complain of numbness between the first and second metatarsals. This was an ongoing complaint up to 5 months post-operatively. At that time she was told that she may have some permanent numbness, which is not uncommon for a lesion of this size and in this area.

Figure 1A.- F.  Sagittal, Axial and coronal T1, T2, gradient echo/inversion recovery sequences were performed on MRI. (A-F)  A very large cystic fluid collection plantarly, deep to the metatarsal bones,  extending from the cuboid posteriorly, to the proximal metatarsophalangeal junction. (A-F)  Lesion invaginates between 1st and 2nd metatarsals with some upward extension. Adjacent musculature uninvolved, but displaced.  No definitive bony involvement seen. (E and F)

 

Figures 2A and B. Intraoperative view of Schwannomma being excised from foot. Dorsal view of schwannoma. Attempt to remove the lesion from dorsal approach. (A) Plantar view of schwannoma being removed from between 1st and 2nd metatarsals. (B)

Figure 3 Intraoperative measurement of schwannomaremoved from the plantar left foot. The Schwannoma measures 8cm (with adjacent stump total length 12cm).

Discussion

Schwannomas are derived from Schwann cells of the neuroectoderm. Their function is to form the myelin sheath of nerves in the peripheral nervous system, which insulates the nerve and facilitates the transmission of an impulse. Also categorized with a neurinoma, neurileomma, or neurofibroma, the schwannoma is a benign encapsulated slow growing tumor. [12,13] Unlike neurofibromas, schwannomas do not traverse through the nerve but remain in the sheath lying on top of the nerve. They have a low risk of metastasizing and do not usually present with underlying systemic disease, such as neurofibromatosis. Schwannomas were found to have some transmission types that were autosomal dominant. [13] As mentioned previously, schwannomas are most common in patients in the second through the fifth decades of life and have no gender or racial predilection. [12] Their size ranges from about 2-20cm in diameter with the smaller tumors appearing white, fusiform, round and firm. The larger tumors are usually irregular, lobulated and grey or yellowish white. [9]

Schwannomas can present with no symptoms, mild symptoms or severe symptoms mostly affecting the nerves. The first case of a solitary neurilemma was discussed by Liebau, who stated that schwannomas should be looked for in all cases where patients present with pain, paresthesia of leg and foot, especially if all other injury has been excluded. [14] Much like the case presented above, research agrees that most patients present after a long delay with complaints of an isolated superficial palpable mass. [15] The tumor was encompassing the plantar aspect of the patient’s foot in this case and her main symptoms were swollen foot which induced pain when wearing shoe gear. Schwannomas can also appear throughout the body usually extracranial, but also found in the pelvis, upper and lower extremity. Schwannomas are commonly found on the flexor surface most likely because nerves trunks are generally larger at this aspect. [1,16] Persing, et al., discussed how a proximal invasion of this tumor at the sciatic nerve caused tarsal tunnel like symptoms. [18]

He spoke of how his patient had an unsuccessful tarsal tunnel release then later removal of the schwannoma from the sciatic nerve alleviated all symptoms in the foot. [17] A similar study by Gominak presents a case in which the posterior tibial nerve was thought to be compressed by the flexor retinaculum. [16] Release of the retinaculum was performed ineffectively. It was later determined that the patient had a thigh schwannoma which, when resected, alleviated all lower extremity symptoms. Therefore when a patient presents with pain in the foot and ankle a more proximal tumor should be investigated if symptoms persist after failed treatment. Nerve sheath tumors are usually initially recognized by MRI. They have an intermediate to moderately bright signal on T1-weighted images, and a bright, heterogeneous signal on T2-weighted images. [12] MRI is useful in identifying the exact location and size of the tumor. However, it is impossible to actually diagnose a schwannoma utilizing MRI alone. The tumor must be surgically excised and sent for pathological evaluation. The pathology report will give the definitive diagnosis of schwannoma and establish whether the lesion is benign or malignant. After surgery symptoms should subside but the patient may continue to have paraesthesia, as the above patient. Motor and sensory abnormalities usually return to normal if the schwannoma is found and resected promptly following initial finding. When they are resected the function of the nerve should not be compromised. [13] With most surgical procedures patients are warned of risk of nerve damage, we must especially warn them of an increase in this risk with surgical excision of a schwannoma. The patient in this case study endured several months of post operative numbness. She has been followed since then and relates no symptoms at this time.

In conclusion, schwannomas are rare solitary nerve sheath tumors. They should always be considered as a differential diagnosis when tarsal tunnel syndrome, neuromas, nerve entrapment or radiculopathy18 is suspected. Schwannomas found in the proximal aspect of the lower extremity can also cause distal symptoms or injury, so this must also be considered, especially if the previous differentials have been ruled out. Early diagnosis can prevent permanent nerve damage, soft tissue or boney deformity.

References

1. Stout AP: The peripheral manifestations of the specific nerve sheath tumor (Neurilemoma) Am J Cancer 24: 751 – 796, 1935.
2. Berlin SJ: Soft Somatic Tumors of the Foot: Diagnosis and Surgical Management. Futura Publishing Co, Mount Kisco, NY: 227, 1976.
3. Stout AP: Tumors of the peripheral nervous system. In Atlas of tumor pathology. Section 2, Fasicle 6. Washington, D.C., Armed Forces Institute of Pathology, 1949.
4. Giannestras NJ, Bronson JL: Malignant schwannoma of the medial plantar branch of the posterior tibial nerve (unassociated with von Recklinghausen’s disease) A Case Report. J Bone Joint Surg 57A (5): 701 – 703, 1975.
5. Verocay J: Zur Kenntnis der Neurofibroma Beitr Pathol Anat 48:1 – 69, 1910.
6. Das Gupta TK, Brasfield RD, Strong EW, Hajdu SI: Benign solitary schwannomas (neurilemomas). Cancer 24: 355 – 366, 1969.
7. Ogose A, Hotta T, Morita T, Yamamura S, Hosaka N, Kobayashi H, Hirata Y: Tumors of peripheral nerves: correlation of symptoms, clinical signs, imaging features, and histologic diagnosis. Skeletal Radiol 28(4):183-8, 1999.
8. Spiegl PV, Cullivan WT, Reiman HM, Johnson KA: Neurilemoma of the lower extremity. Foot Ankle 6 (4): 194 – 198, 1986.
9. Wolpa, ME, Johnson JD: Schwannoma of the fifth digit. J Foot Surg 28 (5): 421 – 424, 1989.
10. Takada E, Ozaki T, Kunisada T, Harada Y, Inoue H: Giant schwannoma of the back. Arch Orthop Trauma Surg 120: 467 –469, 2000.
11. Maleux G, Brys P, Samson I, Sciot R, Baert AL: Giant schwannoma of the lower leg, (Eur) Radiol. 7: 1031 – 1034, 1997.
12. Joyce M, Laing AJ, Mullet H, Mofidi A, Tansey D, Connolly CE, McCabe, JP: Multiple schwannomas of the posterior tibial. Nerve Foot Ankle Surgery 8:101 – 103, 2002.
13. Liebau C, Baltzer AW, Schneppenheim M, Braunstein S,•Koch H, Merk H: Isolated peripheral neurilemoma attached to the tendon of the flexor digitorum longus muscle. Arch Orthop Trauma Surg 123: 98 – 101, 2003.
14. White NB: Neurilemomas of the extremities J Bone Joint Surg 49A: 1605 – 1610, 1967.
15. Masson WP: Experimental and spontaneous schwannomas (peripheral gliomas.) Am J Pathol 8: 367, 1943.
16. Gominak S , Ochoa J: Sciatic schwannoma of the thigh causing foot pain mimicking plantar neuropathy. Muscle and Nerve 21 (4): 528 – 530, 1998.
17. Carpintero P, Gascón E, Abad JA, Ruza M: Foot schwannomas that mimic nerve – Entrapment syndromes a report of three cases. J Am Podiatr Med Assoc 96(4): 344 – 347, 2006.
18. Persing J, Nachbar J, Vollmer D: Tarsal Tunnel Syndrome Caused by Sciatic Nerve Schwannoma. Ann Plast Surg 20 (3) 252 – 255, 1988.


Address correspondence to: Mark Mendeszoon, DPM, Dept. of Surgery, Podiatry Division, Chardon Medical Center, University Hospitals, 13207 Ravenna Rd., Chardon, Ohio 44024

Dept. of Podiatric Surgery, Chardon Medical Center, University Hospital at Geauga, OH.
Submitted while 3rd year resident Dept. of Surgery, Louis Stokes Cleveland VA Medical Center, Cleveland, OH.
Submitted while 3rd year resident Dept. of Surgery, Louis Stokes Cleveland VA Medical Center, Cleveland, OH.
Department of Surgery, Podiatry Division, Louis Stokes Cleveland VA Medical Center, Cleveland, OH.

© The Foot and Ankle Online Journal, 2009