Purpose: Patients with small adenocarcinoma of the lung (SACL) generally have a good prognosis. However, some SACL cases show lymph node metastasis, with poor prognosis. The expression pattern of 11p15 mucins (clustered on the p15 arm of the chromosome 11) is known to change during carcinogenesis in lung cancer.

Experimental Design: We evaluated the expression of the 11p15 mucins (MUC2, MUC5AC, and MUC6) in 79 surgical specimens of SACL cases by immunohistochemical analysis. Lymph node metastasis was estimated by pathological staging.

Results: Six (7.6%) and 11 (13.9%) of the 79 SACL cases showed MUC2 and MUC6 expression, respectively. Three SACL cases showed both MUC2 and MUC6 expression, and a significant correlation was found between MUC2 and MUC6 expression (Fisher’s test, P = 0.033). Six (7.6%) SACL cases showed MUC5AC expression. Five of the 6 cases with MUC2 expression and 6 of the 11 cases with MUC6 expression were had lymph node metastasis. SACL cases with MUC2 or MUC6 expression showed a significantly higher incidence of nodal metastasis than those without expression (P < 0.001 and P = 0.006, χ² test, respectively). There was no significant correlation between MUC5AC expression and nodal involvement in SACL, whereas three of the six cases with MUC5AC expression showed lymph node metastasis. The SACL cases with MUC2 expression had a significantly poorer prognosis than those without MUC2 expression (P = 0.011, log-rank test).

Conclusions: These results suggest that 11p15 mucins MUC2 and MUC6 are related to lymph node metastasis in SACL.