353 A case of epithelioid schwannoma of the finger

Introduction/Objective Schwannomas are benign neoplasms arising from Schwann cells of peripheral nerves. Epithelioid schwannoma is an uncommon histologic variant characterized by epithelioid cytomorphology, often posing a diagnostic challenge due to its resemblance to malignant soft tissue tumors, including epithelioid sarcoma or melanoma. Most cases involve the extremities. Methods/Case Report We present a rare case of epithelioid schwannoma involving the fourth digit of the right hand in a 97-year-old male with a medical history significant for small lymphocytic lymphoma (SLL). The patient reported a long-standing, slow-growing nodule that had recently exhibited increased redness, enlargement, and occasional bleeding. Physical examination revealed a well-demarcated, subcutaneous mass measuring approximately 1.5 × 1.0 × 0.7 cm, with areas of partial epidermal ulceration. An excisional biopsy was performed. Gross examination revealed a firm, yellow-tan mass lacking a distinct capsule. Histologically, the lesion was well-circumscribed and composed predominantly of epithelioid spindle cells arranged in nests and cords. The tumor cells exhibited round to oval nuclei, prominent nucleoli, and eosinophilic cytoplasm. There was no evidence of mitotic activity, necrosis, or cytologic atypia. Immunohistochemical staining showed strong and diffuse positivity for S-100 and SOX10, consistent with Schwann cell lineage. Scattered CD34-positive stromal cells were present in the background. The tumor was negative for cytokeratin, EMA, PRAME, and HMB-45, effectively excluding epithelial and melanocytic neoplasms. Results NA Conclusion Epithelioid schwannomas are rare and may be mistaken for malignant tumors due to their cytologic features. The diagnosis relies on histopathology and immunoprofile. Complete surgical excision is curative, and recurrence is rare. Epithelioid schwannoma should be included in the differential diagnosis of epithelioid tumors of the finger. Accurate diagnosis using histology and immunohistochemistry prevents overtreatment.