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Immunohistochemical detection of parathyroid hormone-related protein in a squamous cell carcinoma arising from mature cystic teratoma causing humoral hypercalcemia of malignancy.

BACKGROUND
Humoral hypercalcemia of malignancy is a cancer-related hypercalcemia caused by the 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 (PTH-rP) is the main humoral factor implicated. Squamous cell carcinoma arising from mature cystic teratoma is a rare diagnosis itself, much less the description of associated hypercalcemia, despite the fact that the normal keratinocytes produce parathyroid hormone-related protein.


CASE
We present a well-documented case of squamous cell carcinoma arising from mature cystic teratoma of the ovary, complicated by hypercalcemia in a patient with high levels of plasma parathyroid hormone-related protein and immunohistochemical evidence of parathyroid hormone-related protein expression by the tumor cells.


CONCLUSION
In this case, the carcinoma cells had already produced PTH-rP in the primary tumor although the serum calcium levels had not been significantly high at surgery. It is therefore suggested that hypercalcemia may have occurred after PTH-rP production had overcome the homeostatic level during the terminal stage.