Development of diffuse cutaneous squamous cell carcinoma in situ after chemotherapy for ovarian carcinoma and remission with PD1-inhibitor

•Patient developed diffuse cutaneous squamous cell carcinoma in situ after one cycle of chemotherapy for ovarian cancer.•Addition of cemiplimab to neoadjuvant chemotherapy resulted in complete response of diffuse cutaneous SCC in situ.•Complete response of PDL1 + stage IV ovarian cancer at the time of surgery with addition of cemiplimab to neoadjuvant chemo. This is a 74-year-old female, initially presenting with malignant pleural effusion, and evaluation revealed programmed cell death ligand 1 (PDL1)-positive stage IV high grade serous ovarian cancer. Following initiation of standard chemotherapy agents, carboplatin and paclitaxel, the patient developed a diffuse, itchy rash over her abdomen, back, and bilateral upper and lower extremities. Biopsy of the rash revealed a diffuse non-resectable cutaneous squamous cell skin carcinoma (cSCC) in situ. Consequently, a PD1-inhibitor was added to her neoadjuvant chemotherapy regimen, which resulted in complete response to both metastatic ovarian and diffuse cSCC in situ at time of surgery.