Malignant epithelioid schwannoma: a light microscopic and immunohistochemical study

Subcutaneous malignant epithelioid schwannoma with cartilaginous differentiation

BACKGROUND

Malignant epithelioid schwannoma is a rare tumor. The aim of this study is to describe a case of subcutaneous malignant epithelioid schwannoma with cartilaginous differentiation.

METHODS

Histological, immunohistochemical, and ultrastructural examinations were performed on a tumor that arose on the back of a 37-year-old woman.

RESULTS

Histologically, the tumor predominantly consisted of small, round or polygonal cells arranged in cords or nests. Immunohistochemical study revealed that the tumors cells were positive for vimentin, S-100 protein, glial fibrillary acidic protein and neuron specific enolase. The cells were negative for HMB-45, keratin, epithelial membrane antigen, and CAM5.2. Electron microscopic study showed closely associated cells with undifferentiated features. The cells were devoid of external laminae and cellular junctions.

CONCLUSION

Malignant epithelioid schwannoma should be pathologically differentiated from other epithelioid tumors with cartilaginous elements.

Fine-needle aspiration of epithelioid malignant peripheral nerve sheath tumor (epithelioid malignant schwannoma)

The epithelioid variant of malignant peripheral nerve sheath tumor (MPNST), also known as malignant epithelioid schwannoma, is a relatively rare and recently characterized clinicopathologic entity. The epithelioid variant of MPNST shares many clinical features with conventional MPNST but is characterized by different histologic and cytologic features. These include a distinctive nesting pattern and an abundance of cytoplasm not seen in histology of conventional nerve sheath tumors. Cytologically, the epitheliod variant shows a propensity to cellular discohesiveness and a plasmacytoid or epitheliod appearance that is in contradistinction to the spindled appearance of the usual MPNST. Herein, we report our experience with fine-needle aspiration (FNA) of two epithelioid malignant schwannomas and discuss the FNA cytologic differential diagnosis.

Mediastinal malignant epithelioid schwannoma

A case of mediastinal malignant epithelioid schwannoma (MES) is reported. The tumor probably arose in the vagal nerve, and the trachea was involved. A few months after excision of the primary tumor, multiple metastases appeared in lung, cervical spine, and neck lymph nodes. Microscopically, the tumor showed a highly cellular area resembling melanoma or carcinoma. Immunolabeling was done for S-100 protein, keratin, and melanoma-associated antigen. Examination of the entire lesion and in situ characteristics of the tumor involving the vagal nerve were helpful in making the correct diagnosis. Mediastinal MES, to our knowledge, has not been reported to date in the English-language medical literature.

Malignant sinonasal epithelioid schwannoma

Malignant schwannomas are rare neoplasms that are seldom found in the head and neck. Few cases have been reported involving paranasal sinuses and none of them was of the "epithelioid" type. In this report, an unusual case of epithelioid malignant schwannoma involving the maxillary sinus, nasal cavity and orbit is presented. The patient was a 27-year-old male with a history of headache, nasal obstruction and epistaxis. Histologically, the tumour had a biphasic pattern with spindle and epithelioid elements which led to a differential diagnosis with malignant melanoma. It had also to be distinguished from other neoplasms, such as squamous cell carcinoma and olfactory neuroblastoma because of it location. Immunohistochemical positivity for S-100 protein, glial fibrillary acidic protein and vimentin together with negativity for HMB-45 and cytokeratins, as well as mesaxon formation detected with electron microscopy were conclusive in the diagnosis. The patient was treated with surgical excision and radiotherapy but local recurrence and metastases occurred, and he died within 1 year after initial diagnosis.