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case_images: Radiologic findings of intestinal obstruction. An abdominal CT examination in an emergency was performed on the patient and revealed extensive dilatation of the transverse colon (red arrows), indicating proximal intestinal obstruction (A, B).
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case_images: Laboratory tests revealed slight increase in squamous cell carcinoma (SCC, 4.79 ng/ml; normal value (n.v.), <2.5 ng/ml), but carcinoembryonic antigen (CEA, 0.962 ng/ml; n.v., <5.093 ng/ml), carbohydrate antigen (CA)-199 (6.82 IU/ml, n.v., <37 IU/ml), CA-50 (2.24 IU/ml; n.v., <25 IU/ml), CA-242 (2.09 IU/ml; n.v., <20 IU/ml), CA-724 (1.77 IU/ml; n.v., <6 IU/ml), alpha-fetoprotein (AFP, 1.61 IU/ml; n.v., <6.05 IU/ml), neuron-specific enolase (NSE, 2.51 ng/mL; n.v., <6 ng/ml), abdominal computed tomography (CT) examination in emergency was performed to him and suggested intestinal obstruction ( Figures 1A, B ).
case_images: Endoscopic features of the patient before surgery. Colonoscopy showed that the cavity was obviously narrow in the ileocecal region (black arrow), which made the endoscope unable to pass through (A, B), but there were no obvious abnormalities in the ascending colon (C), transverse colon (D), descending colon (E), or rectum (F).
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case_images: Gastroscopy showed no obvious abnormalities, and colonoscopy suggested ileocecal intraluminal stricture ( Figures 2A-F ), which made us unable to observe the end of the ileum.
case_images: Abdominal CT examination of the patient when intestinal obstruction occurs again. Coronal images indicated gas and fluid accumulation in the intestine (A), and transverse images revealed ileocecal intestinal wall thickening (B, C). The red arrow indicaes the ileocecal junction.
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case_images: CT examination on 24 September 2021. CT examination revealed a thicker intestinal wall than normal in the ileocecal region, indicating diverticulitis or tumor ( Figures 3A-C ).
case_images: Histopathology of surgical specimens. Postoperative pathology showed signet ring cell carcinoma among moderately-to-poorly differentiated AC in the right colon. Hematoxylin and eosin staining showed signet-ring cell carcinoma (A), and further immunohistochemistry staining showed ki-67 (>80% +) (B), and CK8 (+) (C). Pictures were magnified x100 on the left, x200 in the middle, and x400 on the right.
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case_images: Postoperative pathology revealed that it is a signet ring cell carcinoma with a size of 3 x 2.5 cm among moderately-to-poorly differentiated AC in the right colon ( Figures 4A-C ).
case_images: Pathological aggressiveness and microsatellite instability of the tumor. The tumor occupies about 80% of the whole tumor (A). Immunohistochemistry staining showed E-Cadherin (+) (B), MLH1 (+) (C), MSH2 (+) (D), MSH6 (+) (E), and PMS2 (+) (F), which indicates it is microsatellite instability-low (MSI-L) cancer. Original magnification x4 for (A), and magnification x200 for (B-F).
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case_images: SRCC occupies about 80% of the whole tumor with no heterogeneity ( Figure 5A ). MLH1 (+), MSH2 (+), MSH6 (+), and PMS2 (+), which indicates it is MSL-low (MSI-L) cancer ( Figures 5B-F ). Metastasis was found in the pericolonic lymph nodes (5/17).