Parathyroid hormone-related protein (PTH-rP)-producing lung cancer with psoas abscess-like metastasis and humoral hypercalcemia of malignancy

Abstract

We report a patient with lung cancer associated with psoas abscess-like metastasis and humoral hypercalcemia of malignancy (HHM). A 71-year-old man was hospitalized with exacerbating pain on the left-side of his back and thigh. A computed tomography (CT) scan of the abdomen demonstrated a tumor in the left iliopsoas muscle, first diagnosed as psoas abscess. A chest roentgenogram showed right-sided pleural effusion, and CT scan of the chest demonstrated a tumor in the right lower lobe of the lung. His serum calcium level was 12.8 mg/dl, and parathyroid hormone-related protein (PTH-rP) level was elevated, to 11.1 pmol/l. The patient died of progressive disease, and necropsy specimens were diagnosed as poorly differentiated squamous cell carcinoma. Immunohistochemical staining for PTH-rP was positive in the tumor cells, including the primary and the metastatic lesions. A review of this unusual tumor type is also presented.