Desmoplastic small round cell tumor showing solid proliferation with limited desmoplasia and confusing immunohistochemic
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CASE REPORT
Desmoplastic small round cell tumor showing solid proliferation with limited desmoplasia and confusing immunohistochemical findings: an autopsy report Atsushi Kihara1 · Kazuya Takahashi2 · Ayataka Ishikawa3 · Yusuke Amano1 · Daisuke Matsubara1 · Hiroaki Kanda3 · Naohiro Sata2 · Noriyoshi Fukushima1 · Toshiro Niki1 Received: 14 November 2019 / Accepted: 19 December 2019 © The Japanese Society for Clinical Molecular Morphology 2020
Abstract We herein report a variant case of desmoplastic small round cell tumor (DSRCT) showing limited desmoplasia and confusing immunohistochemical findings. A 26-year-old male was referred for multiple abdominal masses. Laparoscopic biopsy showed only the solid proliferation of small round cells, and he was initially diagnosed with small cell carcinoma. At autopsy, the tumor spread diffusely throughout the abdominal and pelvic cavities. Although the tumor was composed of a predominantly solid pattern of small round cells, multiple samples revealed a fibrous stroma in limited areas only. While immunohistochemistry showed the diffuse expression of desmin, CD99, and bcl-2, epithelial differentiation was unclear with few cytokeratin-positive cells and no staining for the epithelial membrane antigen. Although fluorescence in situ hybridization analysis indicated the EWSR1 gene rearrangement, we were unable to exclude Ewing sarcoma considering the morphological and immunohistochemical findings. The diagnosis of DSRCT was confirmed with a reverse transcription-polymerase chain reaction for EWSR1–WT1 fusion transcripts. DSRCT must be included in a differential diagnosis of small round cell tumors even if desmoplasia is not immediately detected, and thorough sampling and a molecular analysis are mandatory. Keywords bcl-2 · CD99 · Desmoplastic small round cell tumor · EWSR1–WT1 fusion · Fluorescence in situ hybridization · Reverse transcription-polymerase chain reaction · Solid pattern
Introduction Desmoplastic small round cell tumor (DSRCT) was initially described by Gerald and Rosai in 1989 and given its nosological status in a series of 19 cases in 1991 [1, 2]. It is a rare and highly aggressive tumor that commonly affects the abdominal cavity with a young male predominance [2–4]. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00795-019-00242-5) contains supplementary material, which is available to authorized users. * Atsushi Kihara akihara‑[email protected] 1
Department of Pathology, Jichi Medical University, 3311‑1, Yakushiji, Shimotsuke, Tochigi 329‑0498, Japan
2
Department of Surgery, Jichi Medical University, Shimotsuke, Tochigi, Japan
3
Department of Pathology, Saitama Cancer Center, Saitama, Japan
DSRCT is characterized by the chromosomal translocation t(11;22)(p13;q12), resulting in the EWSR1–WT1 fusion [5, 6]. Histologically, DSRCT is typically composed of solid nests of small round cells within a prominent desmoplastic stroma [2–4]. Tumor cells show a polyphenotypic immunoprofile, including epithelial,
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