Primary Cutaneous Rhabdoid Squamous Cell Carcinoma: A Case Report and Review of Molecular Features

This document reports a rare case of rhabdoid squamous cell carcinoma (RSCC) on the scalp of a non-immunosuppressed male in his late 60s. RSCC is an aggressive variant of squamous cell carcinoma characterized by distinct histopathological features and is extremely uncommon in primary cutaneous tumors, with fewer than 10 cases documented. The tumor showed immunohistochemical positivity for p40, CK5/6, and vimentin, retained INI1 expression, and was negative for muscle differentiation markers. Loss of p53 staining was noted, suggesting its role in the tumor's aggressive nature. The DecisionDx-SCC assay classified the tumor as Class 2B, indicating a high risk for metastasis and poor outcomes. This case underscores the importance of recognizing RSCC for its implications in patient management and prognosis.