Mucinous gastric
carcinoma (MGC) is characterized by substantial mucous lakes within
tumors and comprises 3% of gastric
carcinomas at the authors' institute.
METHODS: RESULTS: Patients who had MGC had deeper invasion (P=.003), more frequent
lymph node metastasis (P<.001), more advanced pathologic stage (P<.001), more frequent lymphatic invasion (P<.001), and lower disease-specific survival rates (P<.0001) than patients who had NMGC. However, a mucinous histology per se was not identified as an independent prognostic factor. Negative
mucin 1, cell surface associated (MUC1) status (P<.001); positive
mucin 2, oligomeric mucus/gel-forming (MUC2) status (P<.001); negative
mucin 5AC, oligomeric mucus/gel-forming (MUC5AC) status (P=.036); and negative
mucin 6, oligomeric mucus/gel-forming (MUC6) status (P<.001) were more frequent in MGCs. The frequency of MSI in MGC was not significantly different from that in NMGC. MGCs had a significantly lower incidence of HER-2
protein overexpression (P=.046), HER-2 gene amplification (P=.009), and EGFR
protein overexpression (P=.017) than NMGCs; and multivariate analysis identified EGFR overexpression as
a factor associated with a poor prognosis (P=.047). Patients with MGC who had a predominance of signet ring cells in
mucin pools had poorer disease-specific survival than patients who had MGC with predominant tubular differentiation (P=.017).
CONCLUSIONS: The clinicopathologic and molecular characteristics of MGCs differed from those of NMGCs. Furthermore, the results indicated that EGFR overexpression and histologic subtyping by predominant
tumor cell type in
mucin pools may be helpful for predicting clinical outcome in patients with MGC.