Early stage signet ring cell carcinoma of the colon examined by magnifying endoscopy with narrow-band imaging: a case report

BACKGROUND Signet ring cell carcinoma of the colon and rectum is rare, and most cases are detected at an advanced stage. We present a case of primary signet ring cell carcinoma detected at an early stage by magnifying endoscopy with narrow-band imaging (NBI) and crystal violet staining. CASE PRESENTATION A 73-year-old man visited our hospital for screening colonoscopy. Six years previously, he had undergone endoscopic submucosal dissection (ESD) for early gastric cancer. The pathological diagnosis was a well-differentiated adenocarcinoma, invading into the mucosa without lymphovascular invasion. Colonoscopy revealed a flat elevated lesion with a slightly depressed area, 20 mm in diameter, in the cecum. Further, magnifying endoscopy with NBI revealed that the surface pattern was slightly irregular and microvessels had a regular diameter and distribution in the margin of the lesion, but in the central part of the lesion, irregularity in the tumor surface pattern and form as well as in the diameter and distribution of microvessels was noted. Additionally, due to mucus, avascular areas were also observed. Magnifying endoscopy combined with 0.05 % crystal violet staining showed IIIL and VI pit patterns in the margin of the lesion, and a VI pit pattern in the central part of the lesion; however, due to mucus exudate, this finding could not be established with certainty. The lesion was successfully removed en bloc using ESD without complications. The tumor was composed mainly of signet ring cell carcinoma, partially mixed with moderately differentiated (tub2) and well-differentiated (tub1) adenocarcinomas. The tumor cells infiltrated 250 μm into the submucosal layer and involved lymphatic vessels. Therefore, the patient underwent an additional laparoscopic ileocecal resection, and the resected specimen revealed no residual carcinoma or lymph node metastasis. CONCLUSION In this case report, we present a case of primary signet ring cell carcinoma detected at an early stage and identified by magnifying endoscopy with NBI and crystal violet staining.