Cutaneous Melanocytic Tumor with CRTC1::TRIM11 Fusion: Review of the Literature of a Potentially Novel Entity

SIMPLE SUMMARY: Molecular profiling of unclassified neoplasms has been pivotal in the characterization of new entities. Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion (CMTCT) is a newly described neoplasm that falls into the broad category of diagnostically challenging dermal proliferations with melanocytic differentiation. The aim of this review is to educate colleagues about the clinical, histopathologic, and molecular features of CMTCT, and provide important information on the differential diagnosis. ABSTRACT: “Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion” (CMTCT) is a recently described entity belonging to the family of superficial tumors displaying melanocytic differentiation. Thirteen cases have been reported so far, on the head and neck, extremities, and trunk of adults of all ages (12 cases) and one in an 11-year-old child. Histopathologically, it is a nodular or multilobulated tumor composed of spindle and epithelioid cells arranged in nests, fascicles, or bundles that are surrounded by thin collagenous septa. By immunohistochemistry, the tumor shows variable immunoreactivity for S100-protein, SOX10, and MITF, as well as specific melanocytic markers such as MelanA and HMB-45. The neoplasm’s biologic behavior remains uncertain since the reported cases are limited and the follow-up is short (median 12 months). However, local recurrence and synchronous distant metastasis after 13 years of initial resection has been described in one case. Herein, we present a comprehensive literature review of CMTCT hoping to raise awareness among the dermatopathologists of this potentially novel entity.