Parathyroid-hormone-related-protein-producing thymic carcinoma presenting as a giant extrathoracic mass.

A 53-year-old female with a 9-month history of chest pain presented with a giant anterior chest wall mass. Radiologic examination showed an anterior mediastinal tumor invading the chest wall. Serum calcium and parathyroid hormone-related protein (PTHrP) levels were extremely elevated. Biopsy specimens disclosed a squamous cell carcinoma with Hassall's corpuscle-like keratotic pearls, and an immunohistological study showed a positive staining with PTHrP. The tumor and serum PTHrP concentration markedly decreased following cisplatin-based chemotherapy and radiation. This is the first case of PTHrP producing a thymic carcinoma with the unusual presentation of a large extrathoracic mass.