RESUMO
Objective Primitive neuroectodermal tumor (PNET) is a rare malignant small round cell tumor .This paper aimed to study the clinical and pathological features of primary pulmonary primitive neuroectodermal tumor . Methods We collected 2 cases of primary pulmonary PNET to review the clinical and pathological features .Immunohistochemical staining was used to detect immune mark-ers, and fluorescence in situ hybridization (FISH) was applied to detect EWS translocation. Results 2 patients were aged 33 years and 17 years.Microscopically, the tumor cell was composed of single small round cells in diffusion or in distribution of sheets or beams , with scant cytoplasm , oval or spindle-shaped nucleus , high mitotic count .Irregular tumor necrosis scattered in the tumor along with visi-ble rosette structure.Immunohistochemical study showed that the tumor cells were positive for CD 99, FLI-1 and Syn, while CKpan, EMA, Desmin, CgA, TTF1, CD34 were negative.EWS/FLI1 translocations were detected positive in both the cases .2 patients died 7 months and 32 months after operation , respectively . Conclusion Primary pulmonary PNET is rare , so the selection of appropriate im-mune markers (CD99, FLI-1, Syn) and FISH for the detection of EWS translocation helps to improve the accuracy of diagnosis .