Abstract

Cutaneous melanocytic tumor with CRTC1-TRIM11 fusion (CMCT) is a recently described entity with only 13 cases reported in the literature. This lesion is thought to exhibit clinically indolent behavior. However, a single case demonstrated metastasis 13 years after excision, raising into question its behavior. Histologically, the neoplasm consists of atypical epithelioid to spindled cells that form a well-circumscribed nodule confined to the dermis and subcutis with cytological features including large vesicular nuclei with prominent nucleoli and abundant eosinophilic cytoplasm. Immunohistochemistry shows variable expressivity of melanocytic markers. Currently, it remains uncertain whether CMCT represents a variant of cutaneous clear cell carcinoma versus a malignant Spitzoid melanoma. Definitive diagnosis is made by laboratory evidence of CRTC1-TRIM11 fusion. On the other hand, most clear cell carcinomas harbor a EWSR1-ATF1 fusion [t(12;22)(q13;q12)], and less commonly EWSR1-CREB1 fusion [t(2:22)(q34;q12)]. Additional studies are needed to accurately classify this entity. Herein, we report the first case of CMCT with epidermal involvement in the youngest patient known to be affected to date. This case and the following discussion introduce this entity, its clinical, histopathologic, and genetic characteristics, and it highlights the utility of next generation sequencing in characterizing atypical melanocytic tumors.

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