Peripheral primitive neuroectodermal tumour of the lung: report of two cases

Aims: We report two unusual cases of intrapulmonary small round cell tumour with evidence that they are primitive neuroectodermal tumours. Methods and results: The patients were a 25-year-old woman and a 15-year-old man, in whom mass shadows were found by routine chest radiography. Both tumours were located in the pulmonary parenchyma, and there was no evidence of an extrapulmonary involvement by the tumour. The lesions showed morphological and immunophenotypic features consistent with peripheral primitive neuroectodermal tumour (pPNET). These features included a hypercellular diffuse growth pattern of closely packed small round cells occasionally forming abortive Homer-Wright-type rosettes and intense immuroreactivities to neurone-specific enolase and MIC2 gene product (O13). Unusual chondroid foci were present in one of the cases. This diagnosis was further supported by the cytogenetic and reverse transcriptase-polymerase chain reaction (RT-PCR) findings of the characteristic t(11;22) chromosomal translocation and EWS/FLI-1 fusion transcripts, respectively, in one of the cases. Conclusions: These morphological and cytogenetic findings substantiate pPNET as a subtype of intrapulmonary small round cell tumours.