Nuclear Protein in Testis Carcinoma of the Thorax

Nuclear protein in testis (NUT) carcinoma (NUT-C) is an exceedingly rare and aggressive neoplasm. We herein report a case of a 57-year-old man with a rapidly progressing tumor of the thorax and left pleural effusion. The pathological features and immunohistochemical staining of specimens obtained by a transbronchial lung biopsy initially indicated poorly differentiated squamous cell carcinoma. However, given the clinical presentation along with the additional histopathologic features, NUT-C was considered. Immunohistochemical staining for NUT was positive in the pleural fluid cell block, confirming the diagnosis of NUT-C. This report indicates the utility of immunohistochemical staining for diagnosing NUT in the pleural fluid cell block.