Metastatic porocarcinoma achieving complete radiological and clinical response with pembrolizumab.

A 67-year-old woman presented in 2012 with a crusty nodule on the left lower limb. Histopathological examination at this time reported a poorly differentiated squamous cell carcinoma (SCC). Two years later, she underwent lymphadenectomy and radiotherapy due to unilateral inguinal and pelvic sidewall nodal metastases. The following year she required excision of two subcutaneous lesions, reported pathologically to be SCC metastases. Further imaging following cyberknife radiotherapy to new brain metastases demonstrated widespread metastatic visceral disease. Twelve cycles of carboplatin and capecitabine failed to halt disease progression. In February 2017, she commenced pembrolizumab, achieving an excellent response and currently has no clinical or radiological evidence of disease. Given the unusual behaviour of her cancer, a histopathological review was requested. The diagnosis was revised to that of porocarcinoma (PC). This represents the first documented case of PC treated with immunotherapy. As of March 2019, the patient remains free of disease.