Micro-lymph node metastasis and its correlation with cathepsin D expression in early gastric cancer.

BACKGROUND AND OBJECTIVES: Limited operations for early gastric cancer (EGC) have been recommended based on data from lymph node (LN) metastasis detected by hematoxylin and eosin (HE) staining. Recently, the clinical importance of micro-LN metastasis has been reported. In this study, the indication of limited operations for EGC was re-evaluated based on the data from micro-LN metastasis detected by cytokeratin (CK) immunostaining. Also, the correlation between micro-LN metastasis and lysosomal acidic protease cathepsin D (CD) expression in primary tumors was evaluated. METHODS: A total of 5,949 LNs from 160 patients with EGC were stained by anti-CK monoclonal antibody (CAM 5.2). Also, the 160 primary EGCs were stained by CD. RESULTS: The incidence of LN metastasis increased from 7.5% (12/160) by HE-staining to 27.5% (44 of 160) by CK immunostaining. The incidence of micro-LN metastasis increased according to the depth of tumor invasion (mucosal cancer: 19% and submucosal cancer: 36.8%) and the size of tumors (< or = 1.0 cm: 5.9%, 1.1-2.0 cm: 25.6%, and > 2.1 cm: 31.7%). The CK-staining patterns were classified into the three subgroups (CK-negative, n = 116; single cell type, n = 27; and clustered type, n = 17). The occurrence of cancer recurrence was significantly higher in clustered type (17.6%) than in single cell type (3.7%) and in CK-negative (0%, P < 0.0001). The mean percentage of CD-positive cancer cells of primary tumors in clustered type (17.2%) was significantly higher than in single cell type (12.3%) and in CK-negative (7.5%, P = 0.0036). CONCLUSIONS: The acidic protease CD may play an important role of cancer metastasis in EGC. The limited operation without lymphadenectomy should be indicated for EGC with CD-negative.