Rare Presentation of Schwannoma in the Ankle: A Case Report.

Schwannomas are benign slow-growing tumors that constitute 8% of all soft-tissue tumors. The clinical signs and symptoms are often misinterpreted because of the low incidence, and these tumors are often misdiagnosed. A 39-year-old male patient presented with non-traumatic solitary swelling in the posteromedial aspect of the right ankle that gradually increased in size and was associated with pain. Clinically, the swelling was firm, non-fluctuant, and was not associated with sensorimotor impairment. Surgical excision of the swelling was performed without damaging the surrounding vessels and nerves. The histopathological examination of the excised tumor revealed a schwannoma. Sociedade Brasileira de Ortopedia e Traumatologia. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. ( https://creativecommons.org/licenses/by-nc-nd/4.0/ ).

Introduction

Schwannomas are benign slow-growing soft-tissue tumors that arise from Schwann cells of the peripheral nerve sheaths. They constitute 8% of all soft-tissue tumors. 1 Of all the reported cases, between 12% and 19% are located in the upper extremity, and between 10% to 13%, in the lower extremity. Its common locations are the flexor surface of the extremities, the neck, the mediastinum, the retroperitoneum, the posterior spinal roots, and the cerebellopontine angle. 2 The clinical signs and symptoms are often misinterpreted because of the low incidence, and schwannomas are often misdiagnosed as other soft-tissue tumors, such as neurofibroma.

Case Presentation

A 39-year-old male patient presented to the outpatient department with complaints of a non-traumatic solitary swelling over the posteromedial aspect of the right ankle associated with mild pain. He had noticed the swelling 15 years before, and it gradually increased in size and was associated with pain that was mild to moderate in intensity and intermittent in nature. There was no significant family history.

The clinical findings showed firm swelling over the posteromedial aspect of the ankle measuring 3 × 2 × 2 cm approximately, and it was non-fluctuant, non-pedunculated, non-compressive, and with no transillumination present. There was no sensorimotor impairment in the right leg and foot.

A magnetic resonance imaging (MRI) scan of the leg ( Fig. 1a,b,c ) revealed a well-circumscribed lesion in the subcutaneous plane in the posteromedial aspect of the distal third of the leg abutting underlying soleus and tAchilles tendon with no definitive evidence of infiltration likely benign lesion? neurogenic.

Fig. 1

(a) Magnetic resonance imaging scan (MRI) showing posteromedial swelling over the distal third of the leg in coronal view. (b) MRI showing posteromedial swelling over the distal third of the leg in sagittal view. (c) MRI showing posteromedial swelling over the distal third of the leg in axial view.

We proceeded with the surgical excision of the swelling after we obtained consent and the complications were explained. The skin overlying the swelling was incised in a curved fashion, and a dissection was performed to demarcate the capsule of the tumor that was incised. Further fine blunt dissection was performed circumferentially along the branch of the posterior tibial nerve, with the perineural sheath attached. The tumor was retracted and removed without damaging the surrounding vessels and nerves ( Fig. 2a,b ).

Fig. 2

(a) Intraoperative image showing the tumor attached to the underlying neurovascular tissue, as well as other soft tissues. (b) Fine dissection of the neurovascular structures from the tumor. (c) Measurement of the dimension of the excised tumor.

The nerve was fully preserved and examined before closure. The excised tumor was sent for a histological study ( Fig. 2c ). The postoperative period was uneventful, with good skin healing and well-preserved nerves.

The histopathological examination revealed a Schwannoma ( Fig. 3 ) consisting of Antoni type A tissue, which is composed of highly cellular spindle-shaped cells surrounding the Verocay bodies and Antoni type B tissue, which consists Schwann cells.

Fig. 3

Histopathological slide showing a tumor composed of cellular areas of oval to spindly cells with thin oval nuclei and formation of Verocay bodies (Antoni type A tissue) and loose paucicellular area of Antoni type B tissue.

Discussion

Schwanommas in the lower extremities are limited to less than 10% of all cases, according to a study by Albert et al. 3 Our case is rare, as the literature search results show very few case reports of schwannomas affecting the posterior tibial nerve.

Delay in the diagnosis is often peculiar in cases of tibial-nerve schwanomma; our patient was operated after 15 years of the onset of symptoms. A similar delay in diagnosis, of up to 10 years, was reported by Ghaly. 4 Smith and Amis 5 reported pain in the foot for 8 years before the recognition of a schwannoma, while Nawabi and Sinisi 6 suggested that the mean time to diagnose the schwannoma was of 86.5 months (more than 7 years).

Extracapsular excision is a commonly-used technique 7 that may be associated with the risk of developing postoperative neurological deficits. During tumor dissection, to reduce the risk of damage to the nerve fascicles, Hussain et al. 8 proposed tumor release by incising the capsule far laterally to the path of the nerve and dissecting circumferentially, with the epineural capsule behind to act as a protective covering; in our case, we incised the capsule in the dorsal aspect, as we knew that the nerve was in the ventral aspect. This was followed by dissection until the nerve and further fine dissection separating it from the parent nerve.

The present is a report of a rare location of a schwannoma of the posterior tibial nerve in the posteromedial aspect of the ankle, which was managed by excision, with no neurovascular damage.

Introdução

Schwannomas são tumores benignos de tecido mole, de crescimento lento, que surgem das células de Schwann das bainhas nervosas periféricas. Eles constituem 8% de todos os tumores de tecido mole. 1 De todos os casos notificados, entre 12% e 19% estão localizados na extremidade superior, e entre 10% e 13%, na extremidade inferior. Suas localizações comuns são a superfície flexora das extremidades, o pescoço, o mediastino, o retroperitônio, as raízes posteriores da coluna vertebral, e o ângulo ponto-cerebelar. 2 Os sinais e sintomas clínicos são muitas vezes mal interpretados por causa da baixa incidência, e muitas vezes os schannomas são mal diagnosticados como outros tumores de tecido mole, como o neurofibroma.

Apresentação de caso

Um paciente do sexo masculino, de 39 anos, se apresentou ao ambulatório com queixas de um inchaço solitário não traumático sobre o aspecto posteromedial do tornozelo direito associado a dor leve. Havia 15 anos que ele tinha notado o inchaço, que aumentou gradualmente de tamanho, e estava associado a dor entre leve e moderada e de natureza intermitente. Não havia histórico familiar significativo.

Os achados clínicos mostraram inchaço firme sobre o aspecto posteromedial do tornozelo medindo aproximadamente 3 × 2 × 2 cm, não flutuante, não pedunculado, não compressivo, e sem a presença de transiluminação. Não havia comprometimento sensório-motor na perna direita e no pé.

A ressonância magnética da perna ( Fig. 1a,b,c ) revelou lesão bem circunscrita em plano subcutâneo no aspecto posteromedial do terço distal da perna, encontrando o músculo sóleo e o tendão de Aquiles, sem evidência definitiva de infiltração provável lesão benigna neurogênica?

Fig. 1

(a) Ressonância magnética mostrando inchaço posteromedial no terço distal da perna em plano coronal. (b) Ressonância magnética mostrando inchaço posteromedial no terço distal da perna em plano sagital. (c) Ressonância magnética mostrando inchaço posteromedial no terço distal da perna em plano axial.

Prosseguimos com a excisão cirúrgica do inchaço após o devido consentimento e a explicação das complicações. A pele sobre o inchaço foi incisada de forma curva, e a dissecção foi feita para demarcar a cápsula do tumor, que também foi incisada. A dissecção posterior e fina foi feita de modo circunferencial ao longo do ramo do nervo tibial posterior, com a bainha perineural anexada. O tumor foi retraído e removido sem danificar os vasos e os nervos circundantes ( Fig. 2a,b ).

Fig. 2

(a) Imagem do intraoperatório apresentando tumor ligado ao tecido neurovascular subjacente e outros tecidos moles. (b) Dissecção fina das estruturas neurovasculares do tumor. (c) Medida da dimensão do tumor excisado.

O nervo foi totalmente preservado e examinado antes do fechamento. O tumor excisado foi enviado para estudo histológico ( Fig. 2c ). O período pós-operatório foi tranquilo, com boa cicatrização da pele e nervos bem-preservados.

O exame histopatológico revelou um schwannoma ( Fig. 3 ) de tipo Antoni A, que se caracteriza por células altamente celulares em forma de fuso em volta dos corpos de Verocay, e de tipo Antoni B, consistente de células de Schwann.

Fig. 3

Lâmina histopatológica mostrando tumor composto de áreas de células ovais a células espinhosas, com núcleos ovais finos e formação dos corpos de Verocay (tipo Antoni A) e área paucicelular solta tipo Antoni B.

Discussão

Schwanomma nas extremidades inferiores está limitado a menos de 10% de todos os casos, conforme estudo de Albert et al. 3 Nosso caso é raro, pois os resultados da pesquisa da literatura mostram muito poucos relatos de casos de schwannoma afetando o nervo tibial posterior.

A demora no diagnóstico é muitas vezes peculiar nos casos de schwanomma do nervo tibial. Nosso paciente foi operado após 15 anos dos primeiros sintomas. Atraso semelhante no diagnóstico, de até 10 anos, foi relatado por Ghaly em seu estudo. 4 Smith e Amis 5 relataram dor no pé por 8anos antes do reconhecimento de um schwannoma, enquanto Nawabi e Sinisi 6 sugeriram que o tempo médio para diagnosticar o schwannoma era de 86,5 meses (mais de 7 anos).

A excisão extracapsular é a técnica comumente usada, 7 que pode estar associada ao risco de desenvolver déficits neurológicos pós-operatórios. Durante a dissecção tumoral, para reduzir o risco de danos aos fascículos nervosos, Hussain et al. 8 propuseram a liberação do tumor, incisando a cápsula bem lateralmente ao caminho do nervo e dissecando-a circunferencialmente, com a cápsula epineural por trás, para atuar como cobertura protetora. No nosso caso, incisamos a cápsula no aspecto dorsal, pois sabíamos que o nervo estava no aspecto ventral. Isso foi seguido pela dissecção até o nervo e dissecção mais fina, separando-a do nervo pai.

Relatamos uma localização rara de schwannoma no nervo tibial posterior sobre o aspecto posteromedial do tornozelo, administrado por excisão, sem danos neurovasculares.