PERIPHERAL PRIMITIVE NEUROECTODERMAL TUMOR OF THE LUNG - REPORT OF 2 CASES

Aims: We report two unusual cases of intrapulmonary small round cell t umour with evidence that they are primitive neuroectodermal tumours. M ethods and results: The patients were a 25-year-old woman and a 15-yea r-old man, in whom mass shadows were found by routine chest radiograph y. Both tumours were located in the pulmonary parenchyma, and there wa s no evidence of an extrapulmonary involvement by the tumour. The lesi ons showed morphological and immunophenotypic features consistent with peripheral primitive neuroectodermal tumour (pPNET). These features i ncluded 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 ge ne product (O13). Unusual chondroid foci were present in one of the ca ses. This diagnosis was further supported by the cytogenetic and rever se transcriptase-polymerase chain reaction (RT-PCR) findings of the ch aracteristic t(11;22) chromosomal translocation and EWS/FLI-1 fusion t ranscripts, respectively, in one of the cases. Conclusions: These morp hological and cytogenetic findings substantiate pPNET as a subtype of intrapulmonary small round cell tumours.