Retroperitoneal neurilemoma presenting with humoral hypercalcemia associated with markedly elevated plasma...

A 72-year-old woman complaining of somnolence and thirst was diagnosed to have a hypercalcemic crisis (corrected serum calcium level, 17.4 mg/dl) associated with encephalopathy and nephropathy. Imaging diagnostic techniques demonstrated a retroperitoneal tumor at the median site of right renal pelvis. Hormonal studies revealed that plasma levels of thromboxane B2, prostaglandin (PG) E2, 6-keto prostaglandin F1 alpha (PGF1 alpha) and prostaglandin F2 alpha (PGF2 alpha) were markedly elevated. The tumor was successfully removed by operation; her serum calcium level and PG levels normalized without any treatment indicating that this case belongs to the category of humoral hypercalcemia of malignancy (HHM). Pathologically, this tumor was diagnosed to be a benign neurilemoma. Parathyroid hormone-related protein (PTHrP) radioimmunoassay and Northern blot hybridization for PTHrP mRNA were negative. The current case demonstrates that hypercalcemic crisis could be induced by a curable benign neurilemoma, and suggests that this HHM-like morbidity was associated with markedly elevated plasma PG levels.