A case of desmoplastic small round cell tumor suspected by the findings of endobronchial ultrasound-guided transbronchial needle aspiration cytology (EBUS-TBNA)

Abstract

Background : Desmoplastic small round cell tumor (DSRCT) is a rare malignant tumor of unknown origin that is predominantly found in the abdominal region in young adults. Herein, we report a case of DSRCT which could be suspected by the findings of cytology.

Case : A 15-year-old male patient was admitted to the hospital because of abnormal opacities detected on a plain chest x-ray. Computed tomography and positron emission tomography (PET-CT) revealed multiple tumors in both the lungs, liver, and abdominal cavity, and bilateral enlarged hilar, mediastinal and supraclavicular lymph nodes showing fluorodeoxyglucose uptake on PET. EBUS-TBNA cytology of an enlarged mediastinal lymph node revealed small round tumor cells with irregular and hyperchromatic nuclei. Immunocytochemistry revealed positive staining for cytokeratin and desmin with a globular pattern, and negative staining for CD3, CD20, and CD56. Based on these findings, DSRCT was considered as the most probable diagnosis and rhabdomyosarcoma was considered in the differential diagnosis. Fluorescent in situ hybridization analysis and reverse-transcriptase polymerase chain reaction analysis of a histological specimen revealed split signals for the EWSR1 gene and EWSR1-WT1 fusion transcript, respectively, confirming the diagnosis of DSRCT.

Conclusion : DSRCT can be cytologically suspected based on the morphological characteristics and immunocytochemical findings.