Relation Between Gastrointestinal Mucus Production and Lymph Node Metastasis in Cases of Small-sized Lung Adenocarcinoma

Abstract

Objective. The evaluation of reduction surgery for small-sized lung adenocarcinoma is still being debated, and the indications for reduction surgery in these patients have not been adequately discussed. Gastrointestinal mucus is not secreted by normal alveolar cells, but some lung adenocarcinomas secrete gastrointestinal mucus, and it is reported that the prognosis of patents with lung adenocarcinomas secreting gastrointestinal mucus is poor. We therefore investigated the relation between lymph node metastasis and the secretion of gastrointestinal mucus in surgically treated cases of small-sized lung adenocarcinoma. Methods. We studied 79 lung adenocarcinoma lesions measuring 2.0 cm or less in patients treated by lobectomy and ND2a dissection between 1989 and 1999. We separated the lesions into two groups according to nodal metastasis: the node-negative group (pN0, 60 lesions) and the node-positive group (pN1, 8 lesions; pN2, 11 lesions). We investigated the incidence of lymph node metastasis in relation to gastrointestinal mucus production, which was determined immunohistologically by staining for HGM, MUC2, MUC5AC, and MUC6, in these two groups. Results. Staining for HGM was negative in all samples. MUC2 was detected in 1 lesion (2%) in the nodenegative group and in 5 lesions (26%) in the node-positive group. MUC6 was detected in 5 lesions (8%) in the nodenegative group and in 6 lesions (32%) in the node-positive group. The difference in the frequency of MUC2 and MUC6 production between lesions with and without lymph node metastasis was statistically significant (p<0.001, p=0.006, re-spectively). MUC5AC was detected in 3 lesions (5%) in the node-negative group and in 3 lesions (16%) in the nodepositive group, a difference that was not statistically significant. Conclusion. The frequency of lymph node metastasis was high in patients with small-sized lung adenocarcinoma with lesions immuno-histochemically positive for MUC2 and MUC6. It is essential that MUC2-or MUC6-positive small-sized lung adenocarcinoma be treated by lobectomy combined with mediastinal dissection.