Gastric micropapillary carcinoma: A distinct subtype with a significantly worse prognosis in TNM stages I and II.

Micropapillary carcinoma (MPC) is an aggressive variant of adenocarcinoma, with a high incidence of lymph node (LN) metastasis in several organs, although not yet well described in the stomach. Thus, we compared the clinicopathologic characteristics, including survival data and immunohistochemical profiles of cell adhesion molecules (E-cadherin, β-catenin, IQGAP-1, and CD44v6), of MPCs with those of adenocarcinomas lacking MPC components (non-MPC) in the stomach. We compared 72 MPC cases with 160 non-MPC cases. Most gastric MPCs arose from tubular or papillary adenocarcinomas, and the proportion of MPC components ranged from 5% to 80%. MPCs were characterized by more frequent lymphovascular invasion and LN metastasis (P<0.0001), higher tumor node metastasis (TNM) stage (P=0.019), advanced age (>65 y; P<0.0001), and more frequent CD44v6 and aberrant β-catenin expression (P<0.0001). The overall 5-year survival rates for patients with MPC were significantly worse than those with non-MPC (30% vs. 67%; P=0.002). Furthermore, when it was stratified by TNM stages, the survival rates were distinguished between MPC and non-MPC groups in TNM stages I to II (P=0.0003), but not in TNM stages III to IV. The presence of the MPC component was associated with a significantly worse patient survival by univariate (P=0.0003) and multivariate (P=0.04) analyses in patients with stages I to II gastric carcinoma. In conclusion, recognition of the MPC component in gastric carcinoma is critical, because the MPC component is associated with more frequent LN metastasis and a worse prognosis, especially in stages I to II gastric cancer.