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Case Reports

Abstract

Granular cell tumors (GCT) are soft tissue tumors of Schwann cell origin and are most often benign in nature. Malignant GCT are exceedingly rare and comprise of 1-2% of cases (1). Very few cases of malignant GCT in children have been reported (2, 3) thus relatively little is known about this rare tumor in the pediatric population.  

We report a 9-year-old male with an 18-month history of a growing, exophytic nodule on the right anterior thigh. Histopathologic findings revealed a dermal proliferation composed of predominantly large, polygonal cells with voluminous eosinophilic, granular cytoplasm arranged in sheets and focal elongated and spindled tumor cells. Immunohistochemical staining revealed expression of SOX-10, S100, and CD63 and was negative for pancytokeratin, EMA, desmin, and melan-A. Findings were consistent with granular cell tumor with mild atypia. Surgical excision was performed, which demonstrated a dermal and subcutaneous tumor with nests and sheets of large epithelioid cells, abundant granular to vacuolated cytoplasm, variably sized nuclei with vesicular chromatin, and frequent prominent nucleoli (Figure 2, 3). Involvement of the dermal adnexal structures and small peripheral nerves as well as scattered mitoses were observed.  

A malignant GCT must have three or more of the following histologic criteria: increased cellularity, prominent spindling, high nuclear to cytoplasm ratio, vesicular nuclei with prominent nucleoli, marked pleomorphism, increased mitotic activity (>2 mitoses per 2 mm2) and necrosis (1). This case met four of the histologic criteria and thus was diagnosed as a malignant GCT. Genetic testing on the tissue for aberrations was negative.