Humoral Hypercalcemia of Malignancy: Diagnosis and Treatment*

The diagnosis of humoral hypercalcemia of malignancy begins with a thorough history and physical examination. After confirming the presence of true hypercalcemia, the diagnostic plan should be developed to include testing such as radiography of the thorax and abdomen; ultrasonography of the abdomen; aspiration cytology of lymph nodes and bone marrow; and, potentially, specialized blood tests to determine parathyroid hormone, parathyroid hormone–related protein, ionized calcium, and calcidiol levels. Supportive therapy with diuresis and additional drug therapy (e.g., diuretics and glucocorticoids as needed) helps protect the body from the detrimental effects of hypercalcemia until an etiologic diagnosis is made and more specific therapy initiated. In refractory cases, other therapies, including salmon calcitonin, bisphosphonates, and sodium bicarbonate, may be indicated. Most patients have a good quality of life while the underlying cancer is in remission. The diagnosis of humoral hypercalcemia of malignancy (HHM) can often be established simply by conducting a biochemistry panel and rectal palpation in the dog or a fine-needle aspiration of a peripheral lymph node. In more challenging cases, however, the diagnosis of HHM may require specialized blood tests, diagnostic imaging, biopsies, and assessment of response to therapy. Therapy begins with IV fluids and diuretics, with more aggressive drug treatments as required, and progresses to specific treatment for the underlying neoplastic disease. MEASURING BLOOD CALCIUM The first diagnostic step when hypercalcemia is detected on a routine serum biochemistry panel should be to confirm that it is real. The possibility of spurious test results should be ruled out whenever an elevated total serum calcium (Ca) value appears on a biochemistry panel. Ideally, a fasting sample should be submitted because sample conditions (lipemia or hemolysis) can artifactually increase the total serum Ca values reported by colorimetric analyzers. In the presence of lipemia or hemolysis, it is recommended that the clinical pathology laboratory or n Differentiating humoral hypercalcemia of malignancy with secondary renal dysfunction from renal disease with secondary hypercalcemia