Thymic squamous cell carcinoma producing parathyroid hormone-related protein and CYFRA 21-1.

A 54-year-old man was admitted to our hospital because of dyspnea. Radiographic examination showed an anterior mediastinal mass and pericardial effusion. Serum calcium and parathyroid hormone-related protein (PTHrP) levels were elevated, and serum CYFRA 21-1 level was extremely high. Results of percutaneous needle biopsy under computed tomography guidance led to a diagnosis of moderately differentiated squamous cell carcinoma. Immunohistological staining showed the tumor cells to be positive for PTHrP and cytokeratin monoclonal antibodies. Postmortem findings were considered to indicate thymic carcinoma. Thymic carcinoma is rare, but our case indicates that thymic squamous cell carcinoma can be identified in terms of paraneoplastic hypercalcemia.