Clinicopathologic analysis of lymph node metastasis in surgically resected superficial cancer of the thoracic esophagus.

We examined lymph node metastasis clinicopathologically in 236 cases of superficial cancer (T1, Tis) of the thoracic esophagus surgically resected at our department without adjuvant treatment. Mucosal cancer was observed in 112 cases (47%) and submucosal cancer in 124 cases (53%). Lymph node metastasis was present in 3% of mucosal cancer cases and 41% of submucosal cancer cases. By the recent pathologic subclassification of the extent of the cancerous invasion in superficial esophageal cancer, mucosal cancer and submucosal cancer were each divided into three subtypes according to the extent of invasion, i.e. m1, m2, m3, sm1, sm2 and sm3 cancers. There was no case of lymph node metastasis in m1 and m2 cases, but it was observed in 8% of m3 cases, in 11% of sm1 cases, in 30% of sm2 cases and in 61% of sm3 cases. The number of involved nodes was three or less in m3 and sm1 cases, however four or more involved nodes were observed in 14% of sm2 cases and in 24% of sm3 cases. Positive lymph nodes were found only in the mediastinum in m3 and sm1 cases. On the contrary, they were found extensively in the mediastinum, the abdomen and the neck and in two or more regions in 27% of sm2 cases and in 38% of sm3 cases. Considering the location of positive nodes, the recurrent nerve lymph nodes were most frequently involved, followed by the cardiac lymph nodes. A similar tendency was observed in cases with single node metastasis. The 5-year survival rate of cases from m1 to sm1 was similar. That of sm3 cases was significantly worse than that of other groups. Based on the clinical results, the therapeutic guidelines for superficial cancer of the thoracic esophagus are considered to be as follows: (i) in m1 and m2 cancer, endoscopic mucosal resection is generally indicated in principle, although transhiatal esophagectomy may be indicated in some cases; (ii) in m3 and sm1 cancer, endoscopic mucosal resection is performed initially, then subsequent treatment is selected if necessary; (iii) in sm2 and sm3 cancer, conventional transthoracic esophagectomy with systematic lymph node dissection is indicated.