抄録
A 47-year-old man was admitted to our hospital complaining of anal pain and difficulty in defecation. Gastrografin enema showed marked narrowing of the lumen and spicula of the lower rectum. Colonoscopy revealed circumferential stenosis with edematous mucosa, a coarse cobblestone like appearance, but no ulcer in the lower rectum. Histological findings of biopsy specimens obtained from the first colonoscopy showed non-neoplastic cells. However, the imaging findings and history of present illness strongly suggested the possibility of type 4 colorectal cancer. Therefore, we performed colonoscopy three times until a definitive diagnosis was obtained. A total of 51 biopsy specimens were examined until a signet ring cell carcinoma was detected, which was detected in a specimen only obtained from an erosion. The resected specimen showed marked thickening of the rectal wall. Histological examination revealed transmural invasion by poorly differentiated adenocarcinoma and a signet ring cell carcinoma associated with severe desmoplastic reaction. Type 4 colorectal cancer is an uncommon morphological type of colon cancer. Even many biopsy specimens obtained from non-erosive areas can rarely provide cancer cells, because of the invasive configuration of the cancer. Therefore, multiple biopsies, especially from erosions, are necessary to obtain a definitive histological diagnosis.
