Abstract:

Collision tumors are unusual neoplasms characterized by two distinct tumors within a single lesion. We report the case of a collision tumor composed of sebaceous carcinoma and Merkel cell carcinoma (MCC). An 84-year-old female with remote history of liver transplantation presented with several months of a rapidly growing lesion on the left leg. Physical examination revealed a large, red-violaceous, ulcerated nodule on the left pretibia. Shave biopsy demonstrated sheets of basaloid cells with rare, atypical sebocytes positive for CK5/6, p63, and adipophilin, consistent with sebaceous carcinoma. A second population of round, basaloid cells with smudged chromatin stained positive for CK20 in a perinuclear dot pattern, chromogranin, and synaptophysin, consistent with MCC. Sebaceous carcinoma typically occurs on the head and neck, especially the eyelid, only rarely occurring on the extremities. Merkel cell carcinoma is a primary cutaneous neuroendocrine tumor most commonly seen in elderly patients on sun exposed areas. Recently, the Merkel cell polyomavirus has been implicated in up to 80% of tumors, with the remainder thought to be related to accumulated actinic damage and high mutational burden. Both sebaceous carcinoma and MCC are aggressive neoplasms with high metastatic potential and poor prognosis. Collision tumors involving MCC have been well documented, often with concurrent squamous cell carcinoma or melanoma, likely due to shared risk factors including ultraviolet radiation. Sebaceous carcinoma has been reported in association with squamous cell carcinoma and basal cell carcinoma on the eyelid, but there are no reports in association with MCC. Our case is especially notable due to both the rare types of tumors involved and the unusual anatomic location. The patients long history of immunosuppression may have played a role in the development of these rare neoplasms.

Financial Disclosure:
No current or relevant financial relationships exist.

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Lawrence Kuklinski, MD

Biography