Micropapillary early gastric carcinoma with distinct clinicopathological features, high risk for lymph node metastasis, and dismal prognosis: a multicenter clinicopathological study of 29 cases identified in 1890 early gastric carcinoma radical gastrectomies.

Clinicopathology and risk factors of lymph node metastasis (LNM) in micropapillary early (pT1) gastric carcinoma (MEGC) remain elusive because of the extreme rarity. In this multicenter study, we investigated 1890 consecutive radical resections of early gastric carcinoma diagnosed with the World Health Organization criteria and identified 29 (1.5%) MEGC cases with a small (≥5%) micropapillary component. MEGC showed a male predominance (male-to-female ratio, 21:8). Most (93.1%; 27/29) tumors invaded submucosa. Lymphovascular invasion was detected in 14 (48.3%) of 29 cases. LNM was found in 13 cases (44.8%; 11 identified with a routine hematoxylin-eosin stain and 2 additional cases with a positive pancytokeratin immunostain). Overall, independent risk factors for LNM in early gastric carcinoma included patient age of 62 years or less, female sex, noncardiac location, ulcerative pattern, tumor size of greater than 2 cm, submucosal invasion, Lauren diffuse type, lymphovascular invasion, and MEGC. In MEGC, advanced pathologic stages were demonstrated in 6 (20.7%) of 29 cases. The 5-year overall survival rate of MEGC patients was 58.6%. Submucosal invasion, lymphovascular invasion, and LNM were significantly more frequent in the MEGC group than in the non-MEGC groups. Advanced pathologic stages were significantly more common in MEGC than in nonmicropapillary Lauren intestinal- but not diffuse-type early gastric carcinomas. In conclusion, MEGC demonstrated a high propensity for lymphovascular invasion, LNM with advanced stages, and dismal prognosis.