Cytology of desmoplastic small round-cell tumor

Abstract

Desmoplastic small round-cell tumor (DSRCT) is an aggressive malignancy of young adults, which is amenable to fine-needle aspiration biopsy (FNAB). As this entity is increasingly recognized and biopsied, cytopathologists are compelled to become familiar with the range of cytologic features of DSRCT. In addition, postchemotherapy tumors may be sampled to confirm disease recurrence before planning additional therapy. This study was designed to compare prechemotherapy and postchemotherapy cytomorphology of DSRCT and to evaluate for distinct chemotherapy-induced changes. The authors searched their respective institutional databases for all DSRCT cases with an associated FNAB. FNAB slides, immunocytochemistry, and cytogenetic results were reviewed. Six aspirates from 5 patients were identified, 3 of which were postchemotherapy. The postchemotherapy cases demonstrated cytologic findings not typically described in DSRCTs, including prominent and conspicuous nucleoli, discohesive single-cell architecture, and slightly larger cell size. Cytomorphologic variability was prominent in prechemotherapy cases, and no case could be classified as DSRCT on cytology alone; immunohistochemistry was necessary for definitive diagnosis. Chemotherapy increased the spectrum of cytologic features. The most notable difference between the 2 groups was a predominantly discohesive single-cell pattern with conspicuous nucleoli in the postchemotherapy group, instead of the clustering pattern of medium-sized cells with inconspicuous nucleoli typically attributed to de novo cases reported in the literature.