Primary pulmonary primitive neuroectodermal tumor (PNET) - A case report

We describe a rare case of a primary primitive neuroectodermal tumor (PNET) in the lung of a 17-year-oId girl. Grossly, the tumor, located in the righ t lower lobe, was relatively well-circumscribed and whitish to yellowish in color with scattered hemorrhagic necrosis. Microscopically, the tumor was composed of ovoid to polygonal cells with a high nuclear to cytoplasmic rat io and relatively scant cytoplasm, arranged in solid sheets with intervenin g fine fibrovascular stroma. Immunohistochemically, the tumor was positive for the MIC2 gene product, whereas AE1/AE3, CAM5.2, and a variety of neuroe ndocrine markers such as chromogranin A, synaptophysin, and ProGRP, were ne gative. Three months after the lobectomy, recurrent tumors were noted in th e mediastinum and right thoracic wall, and she died despite combined chemot herapy and radiation therapy. In this case cytogenetic analysis showed a hy pertriploid karyotype with multiple numerical and structural chromosomal ab errations, but failed to disclose distinct evidence of translocation betwee n chromosome 11 and 22. However, the reverse transcriptase-polymerase chain reaction (RT-PCR) demonstrated EWS/FLI-1 fusion transcripts, confirming; t he histopathologic diagnosis of PNET. This case indicates that the primary pulmonary PNET is a highly aggressive neoplasm occurring at a young age, an d should prompt combined systemic chemotherapy, even though it is organ-con fined.