Cutaneous Malignant Squamomelanocytic Tumor: A Case Report of a Rare Neoplasm

Cutaneous squamomelanocytic tumor (SMT) is an exceedingly rare cutaneous malignancy characterized by the presence of both squamous cell carcinoma and malignant melanoma within a single tumor. SMT typically presents clinically as keratotic skin papulonodules, most commonly occurring on the face, scalp, or other sun-exposed areas of middle-aged to elderly White male patients. Owing to the rare nature of this tumor, the histogenesis and prognosis remain relatively unclear. Histopathological examination of the tangential biopsy revealed an invasive cutaneous malignancy consisting of 2 distinct yet closely associated atypical cell populations: (1) a population of atypical squamoid epithelial cells arranged in cords and keratin pearls and (2) a population consisting of atypical, spindled cells with fine melanin pigment arranged in confluent sheets. Both populations of atypical cells emanated in an invasive pattern from the underside of the overlying epidermis into the deep dermis. Squamomelanocytic tumors are among the rarer types of collision tumors between 2 malignant lesions as most are basomelanocytic. For most reported SMTs, the melanoma population comprises epithelioid cell morphology, whereas our tumor is composed of spindled cell morphology. In this article, we exemplify a unique case of SMT in an 87-year-old male patient.