Desmoplastic small round cell tumour of the pleura: a case report with further cytogenetic and ultrastructural evidence of 'mesothelioblastemic' origin

A typical case of desmoplastic small round cell tumour of the pleura in a 2 5-year-old man is described. In addition to the typical histological and im munohistological findings, the EWS-WT1 fusion product was also observed. Ul trastructurally, some tumour cells displayed intracytoplasmic neolumina, wi th short microvilli characteristic of submesothelial cells. These findings support the theory of a splanchnopleuric intraembryonic mesodermal, 'mesoth elioblastemic' origin, both morphologically and cytogenetically.