An Aggressive Case of Occipital Scalp Porocarcinoma: A Case Report and a Review of 20 Cases

Eccrine porocarcinoma (EPC) is a rare and aggressive malignancy of the sweat glands, accounting for a minuscule fraction of all cutaneous tumors. Its occurrence on the scalp, particularly the occipital region, presents significant diagnostic and therapeutic challenges due to unique anatomical constraints and potential for aggressive local behavior . We present the case of a 38-year-old female who presented with a progressive lesion on the right posterior occipital scalp. Initially misdiagnosed and excised as a simple cyst multiple times, the lesion was subsequently identified as an aggressive EPC following a second wide local excision (WLE), which led to the initial definitive diagnosis. Pathological analysis revealed a moderately to poorly differentiated adnexal carcinoma with an 8 mm invasion depth, a high mitotic index (15 mitoses/mm²), and prominent perineural invasion. Notably, lymphovascular invasion was absent. Due to these high-risk features and the recurrent nature of the lesion, adjuvant radiotherapy (60 Gy) was planned. EPC of the scalp is rare, with only 20 cases (including the current case) identified in our systematic review. Management requires wide surgical margins; however, the scalp's tight adherence to the skull often complicates primary closure. Adjuvant radiotherapy is indicated in cases with high-risk features such as depth > 7 mm, high mitotic rate, and perineural invasion to mitigate the risk of local recurrence and regional metastasis.