MUC1 Expressions and Its Prognostic Values in US Gastric Cancer Patients

Simple Summary Although the alteration of mucin (MUC) expression was associated with gastric cancer (GC) prognosis, its prognostic values remain to be elucidated in US GC patients. The positive expression of MUC1 was associated with aggressive pathologic features of GC including diffuse-type cancer, advanced cancer, lymph node metastasis, and distant metastasis. In early GC, patients with a high level of MUC1 expression showed a higher rate of lymphovascular invasion, which is a strong risk factor for lymph node metastasis and noncurative resection after endoscopic submucosal dissection. MUC1 expression can be a useful prognostic marker in US GC patients. This study aims to evaluate the prognostic value of MUC expression in US GC patients. A total of 70 tumor specimens were collected from GC patients who underwent surgery or endoscopic resection between 2013 and 2019 at a tertiary referral center in the US. MUC expression status including MUC1, MUC2, MUC5AC, and MUC6 was evaluated by immunohistochemical staining. The positive rates of MUC1, MUC2, MUC5AC, and MUC6 were 71.4%, 78.6%, 74.3%, and 33.3%, respectively. Patients with positive MUC1 expression had a significantly higher rate of aggressive pathologic features including diffuse-type cancer (42.0% vs. 0%; p < 0.001), advanced GC (80.0% vs. 30.0%, p < 0.001), lymph node metastasis (62.0% vs. 20.0%; p = 0.001), and distant metastasis (32.0% vs. 5.0%; p = 0.017) compared with those with negative MUC1 expression. However, the differences in the pathologic features were not observed according to MUC2, MUC5AC, and MUC6 expression status. In early gastric cancer (EGC), patients with a high level of MUC1 expression showed a higher rate of lymphovascular invasion (71.4% vs. 21.4%; p = 0.026) and EGC meeting non-curative resection (85.7% vs. 42.9%; p = 0.061) than those with negative MUC1. In US GC patients, MUC1 expression is associated with aggressive pathological features, and might be a useful prognostic marker.