Abstract:

Squamomelanocytic tumors (SqMT) are exceedingly rare neoplasms comprised of histologic features of both squamous cell carcinoma and malignant melanoma. Fewer than 50 cases of SqMT have been reported to date, typically in chronically sun damaged skin of older adult, more commonly in males. We report a case of a SqMT in a 72-year-old man, who presented with an erythematous crater-like papule on the forearm. The biopsy of the lesion revealed SqMT, characterized by a malignant neoplasm composed of an admixture of melanoma and squamous cell carcinoma components. S100-cytokeratin AE1/AE3 combination immunohistochemical stain separately stained the two distinct components of the neoplasm, without dual positivity seen in the tumor cells. In-situ component of melanoma was present in the epidermis. The patient was subsequently treated with wide local excision with sentinel lymph node biopsy. The excision specimen showed residual melanoma without the carcinoma component. Three sentinel lymph nodes were negative for malignancy. In this report, we describe this unusual case of SqMT, along with the review of the current literature.

Financial Disclosure:
No current or relevant financial relationships exist.

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Eduardo Rodriguez, MD