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Abdominal computed tomography (CT) (axial plane). A - An abdominopelvic mass (AM) occupying almost whole of the abdominal cavity. The small bowel (SB) is displaced to the left, while the right colon (RC) is abutted against the paracolic gutter; B - Pelvic CT (axial plane) showing right iliac vessels (arrow) adherent to the soft tissue mass.
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The CECT also showed multiple small lesions in the abdomen, with a large right iliac mass abutting the right iliac vessels (Figures 1A and 1B).
Intraoperatively view of the mass possibly arising from the right colon mesentery or the bowel wall of the right colon. A - Distal ileum; B - Multilobulated soft tissue tumor; C - Transverse colon.
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Another mass measuring 8 x 6 cm was seen in the right iliac fossa abutting the iliac vessels (Figure 2). Mitotic figures were occasional (2-4/10 high-power field); necrosis was absent.
Gross view of the specimen after formalin fixation with multiple fatty to solid gray pedunculated masses some of which appeared to arise from the coalescence of the smaller nodules (black arrowhead). Note the variable sizes of these pedunculated (exophytic masses) (white arrowheads); one mass was endophytic (black arrow) projecting within the cecal lumen. The white arrow highlights the ileocecal valve; the black star highlights the external aspect of the largest exophytic mass.
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In places, the larger masses showed indentation/cleavage, and these areas appeared to be the zone of fusion of two or more adjacent exophytic masses, and the cut surfaces of such masses showed the same (Figure 3). Mitotic figures were occasional (2-4/10 high-power field); necrosis was absent.
Photomicrographs of the appendices epiploicae of different size from smallest to the largest with gradual increase in the septal thickness and complexity (A-C), with the smallest one showing essentially normal morphology (A) and the larger one displaying thick septa (C).
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The larger the masses, the more the thickness, complexity, number of septa, and number of septal and atypical adipocytic cells and lipoblasts increased (Figures 4A-4C and 5). Mitotic figures were occasional (2-4/10 high-power field); necrosis was absent.
The largest of the appendices showed a sclerosing phenotype with occasional lobules of fat (H&E, 100X). The hyperchromatic atypical stromal cells are evident.
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The larger the masses, the more the thickness, complexity, number of septa, and number of septal and atypical adipocytic cells and lipoblasts increased (Figures 4A-4C and 5). The large nodules showed only a few lobules of mature fat and dominantly fibrocollagenous areas, giving rise to a sclerosing pattern (Figure 5). Mitotic figures were occasional (2-4/10 high-power field); necrosis was absent.
The largest mass showed extensive myxoid stroma (H&E, 200X).
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The largest nodule showed well-differentiated morphology with central areas of myxoid degeneration and atypical spindle cells in a myxoid matrix (Figure 6). Mitotic figures were occasional (2-4/10 high-power field); necrosis was absent.
Photomicrographs of the nodular mass. A and B - Thick septa separating the lobules of adipocytes. Note the septa with spindle-shaped singly scattered atypical stromal cells with hyperchromatic nuclei (H&E, 40X and 400X, respectively). C - Multivacuolated lipoblast (H&E, 400X). D - MDM2 immunohistochemistry showing strong nuclear positivity in the stromal cells as well as in the adipocytes (100X).
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The septal cells were moderate to highly pleomorphic, singly scattered, spindle-shaped with hyperchromatic nuclei, and inconspicuous to occasional prominent nucleoli and wispy eosinophilic cytoplasm (Figure 7A). Many of these cells displayed bizarre morphology, and giant cells and floret-like cells were also noted (Figure 7B). The larger nodules also showed atypical adipocytes with hyperchromatic nuclei and many scattered univacuolated and multivacuolated lipoblasts (Figure 7C). Mitotic figures were occasional (2-4/10 high-power field); necrosis was absent. Immunohistochemistry for MDM2 (Figure 7D) and S100 showed nuclear positivity in the atypical septal cells, lipoblasts, and many of the mature-looking adipocytes.