VERY WELL-DIFFERENTIATED TUBULAR ADENOCARCINOMA OF THE STOMACH - ITS ENDOSCOPIC AND HISTOPATHOLOGICAL CHARACTERISTICS

Between 1986 and 1991, 31 patients having tubular adenocarcinoma with low cellular and structural atypism (''very well differentiated tubula r adenocarcinoma:'' tub 0) underwent surgery at the National Cancer Ce nter Hospital (NCCH). Histologically, the 31 lesions in the 31 patient s were very similar to those observed in gastric adenoma (World Health Organization) with severe atypism. Their malignancy could be diagnose d only on the basis of cellular atypism, i.e., uneven distribution of chromatin in the nucleus accompanied by irregularity in the size or sh ape of the spindle-form nucleus, abnormal nuclear polarity and/or obvi ous nucleoli. Histologically, the border between the tub 0 and adenoma tous areas ('front line' of carcinoma) could not be identified within the neoplastic lesion, which showed relatively regularly shaped tubuli (less structural atypism). Of the 31 cases, 30 were solitary early ga stric cancer (EGC). Their clinicopathological features were compared w ith those of 34 cases of gastric adenoma, 237 cases of solitary well d ifferentiated (tub 1) and 127 cases of moderately differentiated (tub 2) tubular adenocarcinoma which had been resected at the NCCH during t he same period. Most (75%) of the 30 tub 0 EGCs were type IIc (depress ed) macroscopically, despite their histological similarity to gastric adenoma which showed a high (90%) elevated appearance incidence. The i ncidence of small lesions, <2 cm in diameter, was highest in gastric a denoma (82%), followed by tub 0 (64%), although the tub 0 lesions show ed a wide range of sizes. Small lesions were less frequent in the tub 1 (43%) and tub 2 (33%) cases. The incidence of submucosal invasion wa s significantly lower in tub 0 cases (17%) than in tub 1 (39%) and tub 2 (46%) cases (P<0.05). No lymph node metastasis was seen in tub 0 ca ses, but was seen in 6.4% and 9.4% of tub 1 and tub 2 cases, respectiv ely. With regard to the endoscopic appearance of depressed mucosal can cer, the incidence of encroachment (moth-eaten appearance) on the tips of folds was significantly lower (10%) and the appearance of marginal elevation was significantly higher (79%) in tub 0 than in tub 1 (each P<0.05) or tub 2 (each P<0.01). The results suggest that 'tub 0' can be regarded as a less malignant but not benign tumor, and that its end oscopic characteristics provide valuable information which can be used to ensure that patients receive suitable treatment.