case_images: PMC10722156_01
case_images: Abdominal radiographs and ultrasound. (A,B) Abdominal radiographs after abdominocentesis. (A) Ventro-dorsal image. (B) Right lateral image. The gas-filled bowel is displaced and gathered leftward (black arrow). The opacity assumed to be omental and mesenteric fat is heterogeneously increased (asterisks). (C,D) Abdominal ultrasound. (C) Peritoneal calcification was suspected due to hyperechoic peritoneal change (white arrow) with strong acoustic shadowing (asterisk). (D) Peritoneal fat was multilobulated and showed heterogeneously high echogenicity (white arrow).
case_images: fvets-10-1298736-g001.jpg
case_images: PMC10722156_01_fvets-10-1298736-g001.jpg
case_images: fig1
case_images: Radiographs following abdominocentesis revealed an abnormally heterogeneously high fat opacity in the upper and right mid-lower abdominal areas (Figure 1). Abdominal ultrasonography revealed a multilobulated intestinal mesentery and omentum with focally increased fat echogenicity and a small amount of free fluid in the abdominal cavity (Figure 1).
case_images: Computed tomography. (A) Pre-contrast and (B-D) post-contrast CT images. (A) Broad calcification at the parietal peritoneum (yellow arrow) and small calcified foci at the mesentery (red arrow). (B) Thickened peritoneum showed strong enhancement (green arrow). (C) Gathered omentum and mesentery at the craniolateral abdominal cavity were observed with fat stranding (white arrow), which caused intestinal displacement toward the lower abdomen (asterisk). Surrounding peritoneal effusion (blue arrow) and thickened visceral peritoneum adjacent to the urinary bladder (orange arrow) were also detected. (D) An abnormally dilated descending duodenum with gas was identified (yellow asterisk).
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case_images: PMC10722156_01_fvets-10-1298736-g002.jpg
case_images: fig2
case_images: Computed tomography (CT; Brivo CT 385, GE Hangwei Medical System Co., Ltd., Beijing, China) was performed under general anesthesia in sternal recumbency on next day to achieve an accurate diagnosis and for surgical planning (Figure 2).
case_images: Gross lesions during laparotomy. (A-D) Gross lesions of the abdominal organs during laparotomy. (A) An unusual fibrous membrane (black arrows) covers the abdominal organs and fluids. After incision of the membrane, (B) the omentum (black arrow) looked abnormally lobulated and cranially condensed. (C) The parietal peritoneal wall was calcified (black arrow). (D) Multiple fibrous plaques (green arrows) were observed throughout the peritoneum, especially in the intestines and abdomen. The pancreas (black arrow) also appeared to be atrophied.
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case_images: PMC10722156_01_fvets-10-1298736-g003.jpg
case_images: fig3
case_images: Upon incision of the abdominal wall, a fibrous membrane was observed connecting the wall to the encapsulated abdominal organs and ascitic fluid (Figure 3).
case_images: Histopathological features of the biopsy samples. (A,B) Neoplastic cells form small nests or islands, surrounded by thick fibrosis with basophilic mineralization or mucinous inter or intracellular matrix. The neoplastic cells are characterized by a moderate degree of cellular atypia, a high nuclear-cytoplasmic ratio, prominent nucleoli, and an increased mitotic index. Scale bar = 100 mum for (A) or 50 mum for (B). (C) Bone trabeculae are present at the center of calcified abdominal wall tissue sample, close to neoplastic cell clusters. A number of spindle-shaped stromal cells and red blood cells are interspersed between bone trabeculae. Scale bar = 50 mum. (D-F) Immunohistochemistry staining for WT1 (D), cytokeratin (E) and vimentin (F) on neoplastic cells within the omental fat is presented. Insets revealed cancer cells with a negative WT1 expression (D), while the typical positive result of WT1 should exhibit brownish nuclear staining. Insets demonstrated that cytokeratin-positive cancer cells (red, E) are completely negative for vimentin (F), which is strongly expressed in the stromal cells surrounding cancer cells. Cytokeratin and vimentin staining are observed in the cytoplasm, indicated by the presence of red-colored particles, signifying positivity. Scale bar = 100 mum.
case_images: fvets-10-1298736-g004.jpg
case_images: PMC10722156_01_fvets-10-1298736-g004.jpg
case_images: fig4
case_images: Hematoxylin and eosin (H&E) staining revealed poorly differentiated, invasive malignant neoplasms (mitotic count 5-8 in 10 high powered 0.237 mm2 fields) (Figures 4A-C). The results revealed that over 90% of invasive, poorly differentiated neoplastic cells exhibited strong immunoreactivity to cytokeratin (AE1/AE3) in the cytoplasm (Figure 4E). However, only a few cells within the neoplastic cell population tested positive for vimentin (Figure 4F), aligning with the characteristics of carcinoma. Additionally, immunostaing for Wilm's tumor 1 (WT1) was performed to definitively exclude mesothelioma, and the result was negative (Figure 4D).