Clinicopathological study of mucinous gastric carcinoma

Mucinous gastric carcinoma (MUC) is relatively a rare subtype of gastric carcinoma, and there has been considerable controversiy over the prognosis of this type of carcinoma. In this study we tried to analyze the clinicopathological differences between MUC and other types of gastric carcinoma (non-MUC) and determine whether MUC is associated with a worse prognosis than non-MUC.

We reviewed 645 patients with pathologically confirmed gastric cancer who underwent gastrectomy in our facility during the period from 1975 through 1997. Among them, 20 patients (3.1%) had gastric carcinoma with (MUC), and 625 patients had it without extracellular mucin (non-MUC). In addition, we classified MUC into two groups (well-differentiated type; 7 cases and poorly differentiated type; 9 cases) and analyzed the differences between them.

The MUC tumors were more often located in the lower and the upper third of the stomach (MUC: 55% and 25%, non-mUC: 41% and 18%, respectively). The patients with MUC had more serosal invasion (t3 plus t4; MUC: 45%, non-MUC: 18%), more-invasive carcinoma (Type 3 plus 4; MUC: 60%, non-MUC: 36%) and more lymph-node involvement (MUC: 45%, non-MUC: 38%) than the patients with non-MUC. The patients with MUC were more advanced in stage at the time of diagnosis (Stage III plus IV; MUC: 50%, non-MUC: 26%) and had a higher peritoneal dissemination rate (MUC: 30%, non-MUC: 12%) and a lower curability rate (MUC: 60%, non-MUC: 78%) than the patients with non-MUC. The mean size of tumors in MUC (7.4 cm) was larger than that of non-MUC (5.5 cm). Therefore, the overall 5-year survival rate for MUC patients (33%) was lower than that for non-MUC patients (64%). There were no significant differences between well-differentiated and poorly differentiated subtypes of MUC except for the curability and peritoneal dissemination rates.

The overall survival rate for patients with MUC was worse than that for patients with non-MUC. The poor prognosis was correlated with more advanced stage at diagnosis and more frequent serosal invasion. These results suggest the need to diagnose patients with MUC in the early stage of cancer and that in the case of the advanced stage, wide excision of the surrounding tissues and aggressive lymph-node dissection will be needed.