Case Report
Copyright ©2014 Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Aug 16, 2014; 2(8): 367-372
Published online Aug 16, 2014. doi: 10.12998/wjcc.v2.i8.367
Desmoplastic small round cell tumor with atypical immunohistochemical profile and rhabdoid-like differentiation
Li Liang, Nina Tatevian, Meenakshi Bhattacharjee, Kuojen Tsao, John Hicks
Li Liang, Nina Tatevian, Meenakshi Bhattacharjee, Department of Pathology and Laboratory Medicine, the University of Texas Health Science Center at Houston, Houston, TX 77030, United States
Kuojen Tsao, Department of Pediatric Surgery, the University of Texas Health Science Center at Houston, Houston, TX 77030, United States
John Hicks, Department of Pathology, Texas Children’s Hospital, Houston, TX 77030, United States
Author contributions: Tatevian N, Hicks J and Liang L designed the report, collected the patient’s clinical data and wrote the paper; Bhattacharjee M and Tsao K collected the patient’s clinical data.
Supported by Department of Pathology, the University of Texas Health Science Center at Houston, United States
Correspondence to: Nina Tatevian, MD, Associate Professor, Director, Department of Pathology and Laboratory Medicine, University of Texas Health Science Center at Houston, 6431 Fannin, MSB-2230, Houston, TX 77030, United States. nina.tatevian@uth.tmc.edu
Telephone: +1-713-5005305 Fax: +1-713-5000730
Received: January 4, 2014
Revised: May 3, 2014
Accepted: June 10, 2014
Published online: August 16, 2014
Processing time: 242 Days and 12.1 Hours
Abstract

Desmoplastic small round cell tumor (DSRCT) is a rare, aggressive malignant neoplasm of unknown origin, and is comprised of small round cells with a characteristic desmoplastic stroma. DSRCT typically expresses epithelial, mesenchymal and neural markers simultaneously. We describe a case of DSRCT with an atypical immunohistochemical profile and rhabdoid-like tumor cells on electron microscopy. In the present case, the neoplastic cells were positive only for vimentin, desmin (cytoplasmic membranous pattern) and CD56, and negative for smooth muscle actin, synaptophysin, CD117, CD45, myogenin, CAM5.2, pancytokeratin, WT1, EMA, CD99, neurofilament, CD34 and p53. Ki67 showed a low proliferative activity. Electron microscopy showed focal rhabdoid differentiation. However, INI-1 (SNF-5/BAF47) demonstrated preservation of nuclear positivity in the neoplastic cells. Cytogenetic studies showed translocation t(11;22)(p13;q12) confirming an EWSR1-WT1 translocation characteristic for DSRCT, and t(1;15)(q11;p11.2) of unknown significance. This case is a diagnostic challenge because of atypical immunohistochemical profile and cytogenetic study is crucial in rendering the correct diagnosis.

Keywords: Desmoplastic small round cell tumor; Ultrastructure; Cytogenetics; Rhabdoid cells; EWSR1-WT1

Core tip: We describe a case of desmoplastic small round cell tumor (DSRCT) with an atypical immunohistochemical profile and rhabdoid-like tumor cells on electron microscopy (EM). DSRCT typically expresses epithelial, mesenchymal and neural markers simultaneously. In this case, the neoplastic cells were positive only for vimentin, desmin and CD56 and negative for epithelial and other muscle markers. EM showed focal rhabdoid differentiation, but INI-1 (SNF-5/BAF47) demonstrated preservation of nuclear positivity in the neoplastic cells. Cytogenetic studies showed translocation t(11;22)(p13;q12) confirming an EWSR1-WT1 translocation characteristic for DSRCT, and t(1;15)(q11;p11.2) of unknown significance.