The decision criterion of histological mixed type in "T1/T2" gastric carcinoma--comparison between TNM classification and Japanese Classification of Gastric Cancer.

BACKGROUND

This study was designed to evaluate the clinical significance of undifferentiated component in differentiated T1/T2 gastric adenocarcinoma.

METHODS

Two hundred thirty-one patients who underwent curative gastrectomy were diagnosed pathologically as differentiated type T1/T2 gastric cancer according to Japanese Classification of Gastric Carcinoma (JCGC). The patients were divided into subgroups, pure differentiated type (pure D group, 181 patients) and differentiated-predominant mixed type (D > U group, 51 patients). The clinicopathological features of D > U group were compared with those of pure D group, and also those of undifferentiated-predominant type (U > D group).

RESULTS

Patients in D > U group were more likely to have larger and deeper tumors with lymphatic invasion and metastases than pure D group. However, there was no significant difference in clinicopathological factors between D > U and U > D groups, except for depth of tumor invasion. The postoperative 5-year survival rate of D > U group was significantly poorer than that of pure D group (88% and 98%, P = 0.011). Multivariate analysis revealed the presence of undifferentiated component was an independent prognostic factor.

CONCLUSIONS

The presence of undifferentiated component in differentiated T1/T2 gastric cancer is associated with tumor progression. Therefore, the decision criterion of histological mixed type in TNM classification is better suited than JCGC in T1/T2 gastric cancer.