A 54-year-old man was admitted to the People's Hospital, Lahu-Wa-Bulang-Dai Autonomous County of Shuangjiang, Lincang, Yunnan, China, complaining of abdominal pain, diarrhea, nausea, and vomiting for more than 1 month. He had presented abdominal pain accompanied by yellow, watery diarrhea (two to three times a day) intermittently for the past month, and vomiting could relieve these symptoms at an early stage. However, his symptoms of abdominal pain and vomiting have been getting worse gradually over the last week. Thus, he was hospitalized at the People's Hospital of Shuangjiang on 12 August 2021.
He is nondrinking, nonsmoking, and has a history of renal insufficiency (serum creatinine level: 173.1 umol/L, n.v., 50-90 umol/L) due to renal calculus for 2 years. He has no family history of cancer or other gene-related diseases. On admission, a physical examination showed mild tenderness in the whole belly and a fading gurgling sound. Routine blood tests, coagulation function, hepatitis B, HIV, syphilis, liver function, myocardial enzymes, electrolytes, blood lipids, and glucose were all normal. 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 ). As he presented no fever or chill and maintained diarrhea (three to four times a day), we provided conservative treatment after getting informed consent. Then he was given fasting, gastrointestinal decompression, empirical anti-infection therapy (ampicillin, 4 g, q12 h), and nutritional support for 5 days. When his obstructive symptoms were relieved, he underwent gastroscopy and colonoscopy during hospitalization. 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. We recommended further CT enterography for this patient, but he refused this examination due to the potential risk of recurrent intestinal obstruction. No evidence of vasculitis, fungal elements, tuberculosis, or parasitic infection was found in further laboratory tests. Endoscopic biopsies of the ileocecal region revealed negative histopathology. Thus, he was discharged from the hospital on 20 August 2021, and it was suggested that he have a liquid diet for at least two weeks and be followed up in an outpatient clinic every month. However, he presented with abdominal pain and diarrhea (six to eight times a day) again in 1 month, and it was even worse than before. Immediately, he was admitted to the Department of Emergency at the People's Hospital of Shuangjiang and received an abdominal 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 ). Radiographic examinations of the head, chest, and abdomen excluded distant metastases. Therefore, the patient received laparoscopic right hemicolon carcinoma radical resection in the Department of Surgery on 29 September 2021. 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 ). SRCC occupies about 80% of the whole tumor with no heterogeneity ( Figure 5A ). The tumor invaded the whole layer of the colonic wall and partly nerves. Tumor thrombus can be found in vessels. No cancer invasion was found along the cutting edges of the surgical specimen. Immunohistochemistry staining showed E-Cadherin (+), 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). Afterwards, he was given regular chemotherapy with the FOLFOX strategy. He received a reexamination, including a colonoscopy and abdominal CT, on 8 February 2022, which revealed no obvious abnormalities. The patient was followed up in the Department of Gastroenterology at the People's Hospital of Shuangjiang until the completion of the article (July 2022) with a good prognosis.