Hyperparathyroidism, hypercalcemia, and calcified brain metastatic lesions in a patient with small cell carcinoma demonstrating positive immunostain for parathyroid hormone.

OBJECTIVE

To describe a patient with metastatic small cell lung carcinoma, who presented with hypercalcemia, a high level of intact parathyroid hormone (iPTH), and multiple calcified metastatic lesions in the brain.

METHODS

We review the clinical findings, laboratory data, and results of imaging studies in our patient. In addition, we summarize the previously reported cases of ectopic iPTH-producing tumors.

RESULTS

A previously healthy 50-year-old man had a 2-month history of back pain, hip pain, and weight loss. Physical examination revealed a confused patient with dehydration, cachexia, and tenderness of the neck and both hips. His serum calcium concentration was 19.1 mg/dL, and the serum iPTH level was 107 pg/mL (normal range, 10 to 65). Imaging studies revealed multiple bilateral calcified metastatic lesions in the brain, a cavitary mass in the right lung, and osteolytic lesions in the left femur, pelvis, and spine. Biopsy of the femoral lesion yielded histologic findings consistent with small cell carcinoma. An immunohistochemistry stain was strongly positive for iPTH in the biopsy tissue.

CONCLUSION

Previously, only seven cases of true ectopic production of iPTH from nonparathyroid malignant lesions had been reported, of which only two were in patients with small cell carcinoma. We report the eighth such case and describe an association between hypercalcemia and calcified metastatic lesions, which has not been previously reported.