Desmoplastic small round-cell tumor: A case report on the large cell variant with immunohistochemical, ultrastructural, and molecular genetic analysis

A case of large cell desmoplastic small round-cell tumor (DSRCT) is describ ed. The tumor arose in a 23-year-old man who was found to have a 14-cm-diam eter omental mass during ultrasonographic examination. The patient died 10 months after surgery. Histologically, the tumor was composed of predominant ly large epithelioid cells with foci of anaplasia mimicking metastatic carc inoma. Immunohistochemically, the tumor cells stained with anti-cytokeratin . EMA. desmin, and NSE antisera. Electron microscopy showed secretory lumin a, desmosomes, cell processes with microtubules and electron-dense granules , and focal whorls of intermediate filaments. Reverse transcriptase-polymer ase chain reaction performed on paraffin block-retrieved tissue demonstrate d the EWS/WT-1 fusion transcript characteristic of the t(11;22)(p13;q12). T his case illustrates a less common histological pattern of DSRCT, i.e.. dif fuse large cells, thus supporting the view that this tumor presents a wider morphological spectrum than that previously recognized.