Variant Pseudocystic Desmoplastic Small Round Cell Tumor With Heterologous Mullerian Cysts

Area of Science:

• Oncology
• Pathology
• Genetics

Background:

• Desmoplastic small round cell tumor (DSRCT) is a rare and aggressive sarcoma primarily affecting young males.
• DSRCT typically presents with widespread peritoneal involvement.
• The characteristic genetic hallmark of DSRCT is the EWSR1::WT1 fusion gene.

Purpose of the Study:

• To report a unique case of DSRCT with Mullerian-like ciliated epithelial cysts.
• To highlight a potential variant pattern of DSRCT.
• To contribute to the understanding of DSRCT's diverse histopathological presentations.

Main Methods:

• Case report of a 13-year-old female with acute abdomen.
• Diagnostic laparoscopy revealing a pelvic mass and subsequent peritoneal nodules.
• Histopathological examination including immunohistochemistry (PAX-8+, ER+/PR+) and molecular analysis (EWSR1::WT1 fusion).

Main Results:

• A 2 cm pedunculated pelvic mass with a myxoid and spindle cell pattern was identified.
• The tumor exhibited nests and cords of small cells forming pseudocysts and true cysts lined by ciliated epithelium.
• Repeat laparoscopy revealed numerous similar peritoneal nodules.
• The tumor harbored the EWSR1::WT1 fusion, confirming DSRCT.

Conclusions:

• This case presents a novel variant of DSRCT characterized by Mullerian-like ciliated epithelial cysts.
• The findings expand the histopathological spectrum of DSRCT.
• DSRCT can exhibit diverse patterns, necessitating comprehensive diagnostic evaluation.