case_images: PMC11783216_01
case_images: (A and B) Axial & coronal CT abdomen/pelvis demonstrating a large heterogeneous partially vascular and necrotic mass measuring 11.0 x 15.7 x 15.5 cm within the right lower quadrant of the abdomen/mesentery. The mass extends from the anterior pararenal space and compresses the ascending colon anteriorly. (C and D) Axial & coronal T2 weighted MRI abdomen showing diffuse heterogeneous hyperintense signal. (E and F) Axial T1 & T1 weighted fat saturated postcontrast MR images demonstrating prominent peripheral enhancement of the mass.
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case_images: This mass extended adjacent to the inferomedial aspect of the right hepatic lobe and adjacent to the junction of the second and third segments of the duodenum, with complete effacement of the majority of the ascending colon and with anterior displacement of the proximal ascending colon and portions of the cecum (Fig. 1A and 1B). Further evaluation with MRI was obtained, which similarly showed the large RLQ abdominal mass abutting the ascending colon/cecum, with heterogeneous T2 hyperintense, T1 isointense/hypointense signal, and a predominantly peripheral enhancement pattern (Fig. 1C, 1D, 1E, and 1F).
case_images: (A) Gross specimen of undifferentiated pleomorphic sarcoma. (B) Undifferentiated pleomorphic sarcoma (UPS) involving colonic wall (H&E, x2). (C) At medium power, spindle nuclei are scattered among larger cells growing in a vague storiform pattern (H&E, x10). (D) At high power, many atypical, bizarre cells with increased nuclear to cytoplasmic ratio and hyperchromasia are noted (H&E, x20). (E) The tumor shows strong and diffuse immunoreactivity for Vimentin, a nonspecific marker of mesenchymal origin, typically positive in UPS (Vimentin, x4).
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case_images: Gross evaluation revealed a large multilobulated mass measuring 15.5 x 12.4 x 9.0 cm, focally involving the right colon with transmural extension up to the mucosa with ulceration (Fig. 2A and 2B). Microscopically, the tumor showed a patternless arrangement of hyperchromatic spindle to epithelioid neoplastic cells with abundant highly pleomorphic and bizzare/multinucleated cells with amphophilic cytoplasm and high mitotic rate (Fig. 2C and 2D). The immunohistochemistry workup was negative for any distinct lineage marker, while only positive for CD34 and vimentin (Fig. 2E).