Abstract: 【Abstract】 To report the first case of CRTC1::TRIM11 fusion cutaneous tumor in China. A 53-year-old male patient presented with a progressively enlarging, thickened plaque with ulceration and exudation on the left sole for 3 years. Dermatological examination revealed a skin-colored plaque measuring approximately 2 cm × 2 cm in size on the left sole, covered by thick scaly crusts and circumscribed dark-brown crusts. Histopathological examination of the lesion showed well-circumscribed, unencapsulated, multinodular and coalescing tumor masses in the dermis; the masses were primarily composed of amelanotic epithelioid cells and spindle cells, arranged in a multinodular pattern with sparse stroma; some nodules formed nests, while others exhibited a layered or fascicular pattern; mitotic figures were observed among tumor cells. Immunohistochemical staining demonstrated strong nuclear positivity for SRY-box transcription factor 10 （SOX10） and tripartite motif-containing protein 11 （TRIM11）. Fluorescence in situ hybridization revealed a CRTC1 gene break. RNA transcriptome sequencing confirmed the presence of CRTC1::TRIM11 fusion. A diagnosis of CRTC1::TRIM11 fusion cutaneous tumor was made. The patient received wide local excision of the tumor. No recurrence was observed during 10 months of postoperative follow-up.

Key words: Skin neoplasms, Soft tissue neoplasms, Gene fusion, CRTC1::TRIM11 fusion cutaneous tumor, Dermal nodular tumor