Primary signet-ring cell carcinoma of the colon at early stage: A case report and a review of the literature

Figure 1 A: Colonoscopy revealed a discolored, flat-elevated lesion with central depression, 7 mm in diameter, in the transverse colon near the splenic flexure; B: Chromoendoscopy with 0. 2% indigo-carmine dye showed the depressed area more clearly; C: Magnifying colonoscopy after 0.05% crystal violet staining was attempted but failed to detect the pit pattern for depth estimation, as the depressed area was covered by dense mucus, which could not be removed by repeated water washing.

Figure 2 A, B: Histologically, the resected specimen showed a signet-ring cell carcinoma that had deeply invaded into the submucosal layer, and the vertical cut end of the resected tumor was positive for carcinoma cells.