Porocarcinoma Mimicking Other Malignancies: The Diagnostic Role of NUT1 Expression in Two Cases

Summary: Porocarcinoma (PC) is a rare and aggressive cutaneous malignancy originating from eccrine sweat glands. Its histological overlap with squamous cell carcinoma (SCC) poses significant diagnostic challenges, yet distinguishing between the two is critical due to PC's higher risks of local recurrence and regional metastasis. Immunohistochemical markers, such as NUT expression, have greatly improved diagnostic accuracy. We report two clinically atypical cases of PC confirmed via NUT1 expression. The first presented as a mobile subcutaneous nodule over the patella that was initially diagnosed as SCC based on histology. The second manifested as a verrucous genital nodule, clinically suspected as condyloma acuminata. Both cases exhibited histological features suspicious for SCC and PC but were conclusively identified as PC through NUT expression. These cases highlight the role of immunohistochemical markers for accurate diagnosis as well as surgical and long-term management.