title: Desmoplastic small round cell tumor with sphere-like clusters mimicking adenocarcinoma.
abstract: Desmoplastic small round cell tumor (DSRCT) is a rare and aggressive neoplasm that predominantly affects young men. DSRCT often presents as multiple nodules on the serosal surface and is histologically categorized as a small round cell tumor. However, the cytological spectrum of DSRCT is not fully understood because of its rarity. Here, we report an unusual case of DSRCT that showed spheres of cells without stromal cores in pleural fluid cytology material, a finding that is typically associated with metastatic adenocarcinoma and mesothelioma. The specimen from a simultaneous needle biopsy showed the classic histology of DSRCT, comprising nests of small round cells set in desmoplasia. The diagnosis of DSRCT was further supported by immunohistochemical coexpression of cytokeratin and desmin, as well as Ewing sarcoma breakpoint region 1 gene rearrangement, which was determined by fluorescence in situ hybridization. The unusual cytological finding in this case illustrates a potential pitfall of the cytological diagnosis of pleural fluid or ascites. DSRCT should not be excluded from the differential diagnosis when sphere-like round cell clusters are observed in pleural or abdominal effusion, particularly in young male patients.
authors.affiliation: Division of Pathology and Clinical Laboratory, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Hattori
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshida
authors.forename: Naoshi
authors.initials: N
authors.lastname: Sasaki
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Shibuki
authors.forename: Kenji
authors.initials: K
authors.lastname: Tamura
authors.forename: Koji
authors.initials: K
authors.lastname: Tsuta
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology*; D000328:Adult; D058405:Desmoplastic Small Round Cell Tumor / Q000473:pathology*; D005189:False Positive Reactions; D006801:Humans; D008297:Male; D016066:Pleural Effusion, Malignant / Q000473:pathology*
keywords: cytology; desmoplastic small round cell tumor; pleural effusion