Investig Magn Reson Imaging.  2017 Mar;21(1):51-55. 10.13104/imri.2017.21.1.51.

Extraosseous Ewing's Sarcoma Presented as a Rectal Subepithelial Tumor: Radiological and Pathological Features

• Bae H
• Chung T
• Park MS
• Kim MJ
• Lim JS
• Kim H

• KMID: 2376270
• DOI: http://doi.org/10.13104/imri.2017.21.1.51

Abstract

PURPOSE
Extraosseous Ewing's sarcoma (EOE) of the rectum is extremely rare: only three cases have been reported in the literature and none of these reports described their imaging findings in detail. Herein, we describe the tumor imaging and pathological features in detail.
MATERIALS AND METHODS
We report a case of rectal EOE in a 72-year-old female who received local excision and was provisionally diagnosed with a rectal submucosal spindle cell tumor. We used immunohistochemistry, histopathology, and fluorescence in situ hybridization to characterize the tumor and provide a definitive diagnosis of EOE.
RESULTS
MRI revealed a well-demarcated submucosal tumor with heterogeneous enhancement and hemorrhagic foci in rectum. EOE was diagnosed by positive staining of tumor cells for CD99 and Fli-1 by immunohistochemistry and the presence of the EWSR1 gene translocation by fluorescence in situ hybridization. Although the patient underwent radiation treatment and surgery, the tumor recurred after 4 months as revealed by computed tomography and magnetic resonance imaging.
CONCLUSION
Rectal EOE may present as a rectal submucosal tumor. The understanding of imaging and histological characteristics of this tumor are critical for accurate diagnosis and appropriate aggressive treatment.

Keyword

Ewing's Sarcoma; Extraosseous Ewing's Sarcoma; Rectal submucosal tumor; Rectal MRI

MeSH Terms

Aged
Diagnosis
Female
Fluorescence
Humans
Immunohistochemistry
In Situ Hybridization
Magnetic Resonance Imaging
Rectum
Sarcoma, Ewing*

Figure

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  Fig. 1 Initial colonoscopy image demonstrating a rectal subepithelial tumor.

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  Fig. 2 Rectal MRI: (a) Precontrast T1-weighted axial image, (b) T2-weighted oblique axial image, and (c) contrast-enhanced T1-weighted axial and (d) contrast-enhanced T1-weighted coronal image revealed a well-defined submucosal mass measuring approximately 4 cm in the lower rectum. The mass (arrows) showed heterogeneous enhancement with a focal hemorrhage (arrowheads).

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  Fig. 3 Microscopic examination of the local excised specimen. (a) Hematoxylin and Eosin stain (× 200). Immunohistochemistry of (b) CD99 (× 200) and (c) Fli-1 (× 100). (d) Fluorescence in situ hybridization demonstrated the EWSR1 gene translocation, which confirmed the pathological diagnosis of Ewing's sarcoma (× 1000).

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  Fig. 4 Preoperative imaging studies of the locally recurrent mass. Comparison of (a) CT obtained when the locally recurrent mass (arrow) was detected, and (b, c) MRI obtained 2 months after pelvic irradiation indicated that the size of the mass had partially decreased after irradiation. (b) Upon T2-weighted oblique axial imaging, markedly low T2 signal intensity (black arrow) of the residual lesion suggested that extensive fibrotic change had occurred. (c) Contrast enhanced T1-weighted axial image showed minimal enhancement (white arrow) within the residual lesion.

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