Breast cancers are one of the most common malignancies to be associated with hypercalcemia. Most often the hypercalcemia is due to osteolytic metastases and hence portends a bad prognosis. A significant number of the patients with breast cancers (up to 15%) show hypercalcemia in the absence of metastasis.

Hypercalcemia is relatively common in patients with cancer, occurring in approximately 20 to 30 percent of cases. It is the most common cause of hypercalcemia in the inpatient setting.

• Metastatic breast cancer –> Bone involvement –> Hypercalcemia –> Hypercalcemic crisis –> Oliguria/anuria and mental status changes (somnolence or coma)
• Key idea: Hypercalcemic crisis often only seen when calcium levels are > 14 mg/dL, and calcium levels often do not reach levels > 14 mg/dL except for in setting of malignancy

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