Track: Case Reports

Topic: Melanocytic Neoplasms

Abstract:

Intradermal tumors with melanocytic differentiation harboring a CRTC1::TRIM11 fusion were originally reported as melanocytoma because of the generally indolent behavior of the initially observed cases¹. More recently, cases have been reported with metastases². We report another metastasizing tumor, which presented as 6.4 cm mass on the back of a 16-year-old female. The tumor was composed of amelanotic pleomorphic spindle and epithelioid cells. They were diffusely immunoreactive for Sox10 and S100 protein, focally positive for Melan-A, but negative for PRAME. No melanoma in situ or associated nevus were present. Next generation sequence analysis detected a CRTC1::Trim11 fusion. No mutation, but gene amplifications were found on 8q, including PREX2 and MYC. The patient developed metastases to the lung, lymph nodes, and soft tissue. The tumor has been refractory to multiple treatments.

Most patients with a CRTC1::Trim11 fusion tumor do not experience recurrence after surgical excision of the primary dermal nodule. We present our case to enhance the knowledge of histopathologic, clinical and molecular findings associated with CRTC1::Trim11 fusion tumors. In contrast to other reported cases, the tumor of our patient was histopathologically frankly malignant with multinodular growth, high grade atypia, mitoses and areas of necrosis. Additional gene amplifications were found, which may be relevant for its aggressive behavior. Malignant CRTC1::Trim11 tumors pose a diagnostic and management problem. The diagnosis requires a pathologist considering this tumor type and the availability of a molecular method capable of detecting the gene fusion. The tumors may require alternative treatment options compared to standard treatments for melanomas.

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James Smithy, MD