Abstract

Malignant transformation of hidradenitis suppurativa (HS) to squamous cell carcinoma (SCC) is a rare complication predominantly affecting white male smokers with severe perianal or gluteal HS for an average of 25 years. Hypercalcemia of malignancy (HM) in HS-SCC is a rarer occurrence with only seven published reports in literature. We present a case of a 49-year-old Caucasian man with a history of medically uncontrolled HS of the bilateral buttocks for more than 20 years. He presented to the emergency room with significant gluteal pain and a 30-pound weight loss over the past several months. On admission, his calcium was significantly elevated at 14.6 (8.9 - 10.3 mg/dL), PTH was suppressed at 5 (14 - 67 pg/mL) and PTH-RP elevated at 24 (11 - 20 pg/mL). Paraneoplastic hypercalcemia was suspected, and a subsequent biopsy of his HS showed infiltrating, atypical squamous cells with high nuclear to cytoplasm ratio, prominent nucleoli, and frequent mitotic figures. Given the close location to the anal region, a p16 immunohistochemical stain was performed and was negative. A diagnosis of SCC arising in chronic HS was made, with paraneoplastic hypercalcemia. The tumor was unresectable; with less than 6 months survival expected, the patient was transferred to hospice care. Unlike previous documented cases where HM was diagnosed simultaneously or after tumor diagnosis, HM was diagnosed first and prompted a biopsy in our patient. This case demonstrates the significance of elevated calcium levels as a rare paraneoplastic clue to the development of SCC in chronic HS.

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