Pembrolizumab is a humanized monoclonal antibody that blocks the programmed cell death 1 (PD-1) pathway, thereby enhancing antitumor immunity. As the use of immune checkpoint inhibitors becomes more prevalent, so do immune-related adverse events associated with their use. The immune-related adverse events linked with this class of drugs are commonly seen and most of the time are classified as mild adverse events. These are easily treated with steroids if recognition of symptomatology and treatment are promptly established. However, neurologic immune-related adverse events are less understood and have been infrequently cited in the medical literature, thus representing a challenge for clinicians.

Squamous cell carcinoma in situ (SCCIS) of the skin is relatively common. When the authors reviewed 3846 cutaneous SCCIS cases over an 18-month period, they found 6 distinct histopathologic subtypes of SCCIS, 5 of which demonstrated multicentric variants. Multicentric variants of SCCIS were noted on nongenital and nonmucosal skin. All of the multicentric cases that were studied with p16 immunohistochemistry were positive in the tumor cells, suggesting a possible role of human papillomavirus in tumorigenesis. The authors believe that human papillomavirus likely plays a part in the development of these multicentric cutaneous SCCIS.

Hepatocellular carcinoma (HCC) is uncommonly observed as a cutaneous metastasis. We report a 76-year-old man with metastatic HCC to the skin of the nasal ala, diagnosed antecedent to the primary tumor. HCC was confirmed by positive immunostaining with Hep Par 1 in tissue from the metastasis and from a needle biopsy of the primary lesion. In addition, tumor cells from both the metastasis and liver stained positive with HMB-45. To our knowledge, HMB-45 positive staining has not been reported in either primary or metastatic HCC.

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