CRTC1::TRIM11 Cutaneous Tumor Mimicking Primary Dermal Melanoma: Case Report With Literature Review.

CRTC1::TRIM11 cutaneous tumor (CTCT) is a newly identified dermal amelanotic tumor that shows epithelioid to spindle cell morphology with melanocytic differentiation and harbors an in-frame translocation, CRTC1::TRIM11. Given the limited number of reported cases describing its biologic behavior, it is crucial to distinguish this entity from histopathologic mimics, including clear cell sarcoma and metastatic or primary dermal melanoma. Herein, we report a 39-year-old woman with CTCT on the left leg histopathologically mimicking dermal melanoma. The patient developed a tender nodule on the left lateral malleolus 1 year before presentation, which enlarged gradually. A punch biopsy from the lesion and subsequent excision demonstrated a dense spindle cell tumor in the dermis. There were fascicles of achromic spindle cells, some of which showed mildly enlarged nuclei. A mitotic rate of 4/mm2 was noted. The lesional cells were diffusely positive with SOX10 and MITF, with rare S100 and HMB45 staining. Melan-A, pan cytokeratin, p63, and smooth muscle actin were negative. With detection of CRTC1::TRIM11 by next-generation sequencing and lack of CCS-associated cytogenetic translocations, a diagnosis of CTCT was established. She was treated with Mohs micrographic surgery. No metastasis or local recurrence has been found in the 22 months since treatment. Although CTCT was once thought to behave more indolently than melanoma or clear cell sarcoma, recent reports with long-term follow-up detail occurrence of regional and/or distant metastases. Further studies on treatment and follow-up management strategy are warranted.