Parathyroid hormone‐related protein as a potential tumor marker: A case report of ovarian clear cell carcinoma

Hypercalcemia is one of the important paraneoplastic syndromes, mostly occurring in patients with advanced cancer. Clear cell carcinoma is known to be one of the most common histological subtypes of ovarian tumor associated with hypercalcemia. We present a case of ovarian clear cell carcinoma with hypercalcemia caused by elevated serum parathyroid hormone-related protein (PTHrP). PTHrP mRNA and protein were detected by reverse transcription–polymerase chain reaction and immunohistochemical analysis in the primary and metastasis lesions. Serum calcium and PTHrP levels returned to normal after antihypercalcemic treatment and a radical operation, but they elevated along with the recurrence. Because tumor markers such as carcinoembryonic antigen, carbohydrate antigen (CA)125 and CA19-9 were unstable owing to the patient's liver cirrhosis and were not reliable data for management, serum calcium and PTHrP levels are shown to have been a potential indicator of the recurrence in this case.