Epithelioid malignant schwannoma

Abstract

We report a light and electron microscopic, immunohistochemical, clinical and prognostic study of 14 patients with epithelioid malignant schwannoma. In 8 patients the tumour involved a major nerve. The tumours were rather small in most instances, the largest diameter being less than 5 cm in 7 cases. Light microscopically, they showed highly cellular areas of epithelioid, polygonal or rounded cells characteristically forming cords and rows and arranged in nodules of varying size. Spindle cell sarcoma areas as in classical malignant schwannoma were seen in 9 cases, and neurofibromatous areas in one case. Four cases were entirely epithelioid in appearance. Electron microscopically the epithelioid tumour cells showed nuclei with mostly even contours containing one or two trabecular or reticular nucleoli, cytoplasmic projections, intra-cytoplasmic myelin-like figures, intercellular junctions and discontinuous, sometimes multilayered external lamina material. The ultrastructural findings indicate that epithelioid malignant schwannoma is a tumour of neural crest derivation having features of Schwann cell differentiation. Immunohistochemically, S-100 protein was demonstrated in 7 tumours and neuron specific enolase in 3. There was a female predominance, 9/14, and a median age of 38.5 years (range 17-74). The extremities, including the hip and shoulder regions, were the most common sites, 12/14. The tumour proved highly malignant; 9 of 14 patients were dead at the time of follow-up and a high incidence of metastasis (7 of 14) was observed.

Cytologic Features of Malignant Peripheral Nerve Sheath Tumor

“…Although not performed on our material, electron microscopic examination may be of great diagnostic help. Ultrastructural features of both spindle and epithelioid MPNST are characteristic 5,8 and may be very useful to differentiate this tumor from metastasic carcinoma, malignant melanoma and other primitive soft tissue tumors.…”

“…5,8 We had the opportunity to study four cytologic samples from two patients with epithelioid tumor variants. Patient 9 had NF1, and the diagnosis of epithelioid MPNST was present when positive sputum samples were evaluated, allowing a specific cytodiagnosis.…”

Fine‐needle aspiration cytology and core biopsy of malignant peripheral nerve sheath tumor of the uterus: A case report

“…However, ancient schwannoma lacks the prominent nucleoli and mitotic figures often seen in MPNST. 16 Several variants of MPNST have been described, including malignant triton tumor (with skeletal muscle differentiation), 17 as well as the glandular 15 and epithelioid 18 MPNST. A cytodiagnosis of anaplastic and epithelioid MPNST is difficult by FNA.…”

“…3 Epithelioid MPNST resemble carcinoma and malignant melanoma. 18 Ancillary studies including immunohistochemistry and electron microscopy are important tools in confirming the diagnosis of these rare variants of MPNST.…”

Tumor Maligno de la Vaina del Nervio Periférico del Mediastino en un Paciente con Neurofibromatosis Tipo 1

“…En la variante epitelioide, que correponde al 5% de los TMVNP, se observa una lesión neoplásica maligna de origen mesenquimal compuesta por células epitelioides con un citoplasma acidofílico; esta variante es la más frecuentemente vista en transformación maligna de los neurofibromas no asociados con neurofribromatosis; a nivel de inmuno-histoquímica, esta lesión presenta reacción a HMB45, por lo que se debe plantear el diagnóstico diferencial con un melanoma desmoplástico, para lo que es de gran ayuda la positividad inmunofenotípica que muestra esta lesión para el producto del gen 9.5 y la negatividad para la proteína S100 (Lodding et al, 1986). Por otro lado, el tumor maligno de Tritón, o TMVNP con diferenciación rabdomio-sarcomatosa, descrito inicialmente por Masson en 1932, fue denominado así debido a que puede ser inducido al contacto por las salamandras tipo Tritón; trabajo realizado por Locatelly en 1925 (citados por Stasik & Tawfik, 2006).…”