A Case of Adolescent Girl with Hypercalcemia Resistant to Medical Treatment Due to Giant Breast Fibroadenoma

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Hypercalcemia in children is a rare condition and can result from various etiologies such as genetic, metabolic, iatrogenic and malignancy. In some malignancies, Parathyroid Hormone Related Protein (PTHrP) can mimic the physiological effects of Parathyroid Hormone (PTH) and cause hypercalcemia. In this report , we present a rare case of hypercalcemia secondary to juvenile fibroadenoma, which is a benign breast tumor. A 14-year-old girl presented with a complaint of solid breast mass. Further evaluation with ultrasonography and trucut biopsy, a diagnosis of 14x8 cm juvenile fibroadenoma was made. Laboratory examination revealed hypercalcemia (13.9 mg/dl) and high PTHrP (>24.8 ng/L) although the patient was asymptomatic. Despite pharmacological treatment, the patient continued to experience persistent hypercalcemia and subsequently underwent a successful surgical excision. Serum calcium and PTHrP levels normalized postoperatively. Hypercalcemia secondary to malignancy in children is rare and calcium elevation is usually mild-moderate and asymptomatic. In this case, PTHrP was elevated in breast fibroadenoma, demonstrating that hypercalcemia can also occur in benign tumors. The follow-up data of our patient after surgical treatment supports the notion that PTHrP-related hypercalcemia does not always indicate a poor prognosis. This case emphasizes the importance of considering benign tumors such as juvenile fibroadenoma as a potential cause of hypercalcemia in adolescents.