Background: It is important to clarify the clinicopathologic characteristics of micrometastasis in lymph nodes and microinvasion in primary lesions for the treatment options with regard to submucosal gastric cancer.
Methods: We examined 1945 lymph nodes and 68 primary tumors resected from 79 patients with submucosal gastric cancer. Two consecutive sections were prepared for simultaneous staining with ordinary hematoxylin and eosin and immunostaining with anticytokeratin antibody (CAM 5.2), respectively.
Results: The incidence of nodal involvement in 79 patients with submucosal gastric cancer increased from 13% (10/79 patients) by hematoxylin and eosin staining to 34% (27/79 patients) by cytokeratin immunostaining. Micrometastases in the lymph nodes were found in 17 of 69 patients (25%), with cancer-free nodes examined by hematoxylin and eosin. Microinvasion to the muscularis propria was found in 11 of 68 patients (16%) who were histologically diagnosed with submucosal gastric cancer. Survival analysis demonstrated a lesser 5-year survival in the patients with micrometastasis in lymph nodes (82%) and with microinvasion to muscularis propria (73%). A high incidence of nodal involvement was found in submucosal cancers of large size (> 2 cm; 43%), a depressed type (48%), lymphatic invasion (73%), and deeper submucosal invasion (submucosal 3, 53%). A higher incidence of microinvasion was found with the diffuse-type carcinoma (33%).
Conclusions: Cytokeratin immunostaining is useful for detecting micrometastasis and microinvasion in submucosal gastric cancer. Tumor size, macroscopic type, lymphatic invasion, and the depth of submucosal invasion are strongly associated with lymph node involvement.