Immunohistochemical detection of parathyroid hormone-related protein in a cutaneous squamous cell carcinoma causing humoral hypercalcemia of malignancy.

Humoral hypercalcemia of malignancy is a cancer-related hypercalcemia caused by production of humoral factors by malignant cells in patients without bone metastases. Squamous cell carcinomas are the tumors most frequently associated with humoral hypercalcemia of malignancy, and parathyroid hormone-related protein is the main humoral factor implicated. In spite of the fact that normal keratinocytes produce parathyroid hormone-related protein, it is highly unusual for patients with squamous cell carcinomas of the skin to present with humoral hypercalcemia of malignancy. We present a well-documented case of cutaneous squamous cell carcinoma complicated by hypercalcemia in a patient with high levels of plasma parathyroid hormone-related protein and immunohistochemical evidence of high parathyroid hormone-related protein production by the tumoral cells.