A rare case of primitive neuroectodermal tumor of the right lung

A very rare case of primitive neuroectodermal tumor (PNET) of the lung is reported. A 25-year-old female was admitted to our hospital for right chest and back pain. The transbronchial aspiration cytology of a tumor located in the right lower lung lobe revealed the following findings: loose clusters of cells, bloody background, small rounded cells, scanty cytoplasm, and molding. Based on these findings, she was diagnosed as having a small cell lung cancer. Two courses of chemotherapy were then performed followed by surgical resection. Unfortunately, multiple bone metastasis developed 5 months after the operation, and she died one month later. The expression of MIC 2 and neuron-specific enolase (NSE) was examined on cytological and tissue specimens, using an immunohistochemical method with specific monoclonal antibodies. Since both antigens were defective in tumor cells, the final diagnosis was PNET of the lung. We discuss herein the differential diagnosis of small round cell malignant tumors cytologically, emphasizing that the immunohistochemical stain using anti-MIC 2 and anti-NSE antibodies was quite useful for making the precise diagnosis of PNET.