CRTC1::TRIM11-fusion tumor with rare sinonasal presentation and locally aggressive disease course

Abstract Introduction/Objective Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion (CMTCT) is a rare dermatological neoplasm that has not yet been formally recognized by the World Health Organization. At present, our knowledge of this disease is limited to single reports and a series 41 cases with limited follow-up information. It is typically described as a skin lesion expressing melanocytic makers, often leading to its misdiagnosis as melanoma or clear cell sarcoma. CMTCT is regarded as an indolent tumor with infrequent recurrence after complete surgical excision. However, we present a case with uncommon sinonasal presentation and metastasis after multiple resections. Methods/Case Report A 23-year-old woman presented with a right nasal vestibule mass, requiring partial rhinectomy in a foreign country, where she subsequently received chemoradiation. Her tumor at the time was diagnosed as a mucosal melanoma. Eleven years following initial presentation, she demonstrated a recurrent right nasal tumor, as well as neck mass, cervical lymphadenopathy, and lung nodules. The patient then underwent a nasal endoscopic resection and modified neck dissection, which demonstrated a high-grade neoplasm with intersecting fascicles of medium-to-large monomorphic cells; whole exome and whole transcriptome sequencing performed on the resected neck mass identified a pathogenic TERT c.-146C>T alteration and CRTC1 exon 1::TRIM11 exon 2 fusion. The patient is currently alive and undergoing post-surgical chemoradiation. Results (if a Case Study enter NA) NA Conclusion This case expands our understanding of CMTCT and emphasizes its potentially aggressive behavior. The sinonasal presentation contrasts the tumor’s typical appearance on the skin and could mimic mucosal melanoma. Of note, our patient developed recurrent disease and distant metastases, thereby emphasizing the possible role of systemic therapy and suggesting that simple surgical excision may not be curative in all cases. Our case illustrates that CMTCT is an uncommon and potentially misidentified neoplasm, but that its proper diagnosis is essential for treatment selection and follow up.