Objective  We aimed to investigate the clinicopathological features of desmoplastic small round cell tumor (DSRCT).

  Methods  We conducted a retrospective analysis of the clinical characteristics of 7 DSRCT specimens collected from January 2012 to November 2019 in Beijing Shijitan Hospital, Capital Medical University. Pathological slides were further studied. Immunohistochemistry and fluorescence in situ hybridization (FISH) were carried out to study the pathological characteristics.

  Results  The patients were all male with the median age of 29 years. All tumors were located in the abdominal cavity. The clinical symptoms were abdominal distension, abdominal pain, altered bowel habits, and dysuria. Gross pathology showed multiple grey nodules scattered on the omentum and mesentery. Histopathology showed well-defined nests of small round blue tumor cells separated by abundant desmoplastic stroma. Immunohistochemistry showed distinctive expression of paranuclear dot-like pattern of Desmin and Vimentin; expression of EWSR1-WT1 fusion gene was detected by FISH. At the median follow-up period of 15 months, six patients were alive.

  Conclusions  DSRCT is highly malignant, with distinctive pathological features of paranuclear dot-like expression of Desmin and Vimentin by immunohistochemistry, and the expression of EWSR1-WT1 fusion gene.