LAUSR

Background/Aim: SMARCB1(INI1)-deficient cutaneous carcinomas are an emerging subset of rare tumors, with only a few cases reported, making its diagnosis challenging. Case Report: A 84-year-old male with a history of prostate adenocarcinoma and skin squamous cell cancer presented with a rapidly growing upper neck mass. Computed tomography (CT) and positron emission tomography (PET)/CT scans were suspicious of a salivary gland neoplasm of the parotid glands. Needle core biopsy of the right parotid gland mass showed poorly differentiated carcinoma. The patient underwent bilateral superficial parotidectomies and neck lymph nodes dissection. Histologically, the tumor showed rhabdoid and plasmacytoid morphology with diffuse loss of SMARCB1, positive deltaNp63 (p40), focally positive synaptophysin, and 80% of Ki67 index. Retrospectively, SMARCB1 deficiency carcinoma with squamous and neuroendocrine differentiation was confirmed in the prior skin lesion of the right frontal scalp. The patient had a poor prognosis even though post-surgical radiation therapy was given. Conclusion: We present a unique case of metastatic SMARCB1-deficient cutaneous carcinoma in the parotid glands with both squamous and neuroendocrine differentiation. This entity should be considered in any difficult-to-classify skin carcinoma, as timely definitive diagnosis will be mandatory for optimizing therapy.