Hypercalcemia affected in metastatic breast cancer patients without bone metastasis: report of three cases

BACKGROUND: Since humoral hypercalcemia of malignancy (HHM) in breast cancer patients without bone metastasis is rare, the clinical features of this condition are not fully understood. CASE PRESENTATION: During the recent 12 years, 3602 patients were diagnosed with breast cancer in our institution, and only three patients developed HHM without bone metastasis. They were all recurrent breast cancer patients with visceral metastases including the lung and the liver. It took no more than 2 months since symptomatic onset to hospitalization because of hypercalcemia. The maximum serum calcium concentrations were 15.0 mg/dL or higher. All patients had symptoms related to hypercalcemia. Treatment of hypercalcemia including hydration, calcitonin, bisphosphonate, and diuretics was initially effective in the three patients. However, two of three cases were eventually fatal because of unsuccessful treatment of breast cancer. CONCLUSIONS: The common features of HHM without bone metastasis in breast cancer patients include acute onset, severe symptomatic hypercalcemia, and presence of visceral metastasis. Treatment of hypercalcemia decreased serum calcium level in a short period, while successful treatment of breast cancer was essential for a long-term management of HHM. This report provides a consideration to help elucidate the pathophysiology and medical care of breast cancer patients with HHM without bone metastasis.