A Case of PTHrP-producing Juvenile Giant Fibroadenoma Associated with Hypercalcemia

Abstract

Hypercalcemia associated with malignant tumors is frequently encountered in clinical practice. One of the mechanisms that leads to hypercalcemia is the production of PTHrP, an osteoclast-activating factor, by tumor cells, which promotes bone resorption. While most PTHrP-producing tumors are malignant, we report a case of a benign juvenile giant fibroadenoma. A 15-year-old female presented to our department with a 20-cm mass in her right breast. The patient experienced gastric discomfort and fatigue. Blood tests revealed a serum calcium level of 12.4 mg/dL, accompanied by elevated PTHrP levels. Needle biopsy of the mass revealed a fibroadenoma with no malignant findings. The right breast mass was surgically resected ; however, no malignant findings were observed. Immunohistochemical staining revealed PTHrP production in the ductal epithelium of the tumor. Postoperatively, the blood calcium levels returned to normal, and the symptoms improved. To the best of our knowledge, no cases of benign breast tumors associated with PTHrP-mediated hypercalcemia have been previously reported.