Metastasizing intramucosal gastric carcinomas. Well differentiated type and proliferative activity using proliferative cell nuclear antigen and Ki-67.

BACKGROUND

Recently, endoscopic surgery for small superficial gastric carcinomas has become increasingly more challenging, and the treatment criteria remain controversial.

METHODS

To examine the metastatic potential of intramucosal gastric cancers (IMGCs), IMGCs with regional lymph node involvement (NI) were compared with IMGCs without regional lymph NI clinicopathologically. To clarify the metastatic behavior of well differentiated adenocarcinoma (W-type), immunohistochemical staining using Ki-67 and proliferating cell nuclear antigen (PCNA) monoclonal antibodies were performed.

RESULTS

Of the 943 lesions with IMGC, 21 (2.2%) were NI on histologic examination. There was no significant difference between the macroscopic classification and the incidence of NI. The sizes of the IMGCs with NI (median, 4.3 cm) were significantly larger than the IMGCs without NI (median, 2.4 cm). Among the histologic grades classified according to the predominant features, the incidence of NI in poorly differentiated adenocarcinoma (P-type) (12/304, 3.9%) was significantly higher than that in well differentiated (W-type) (6/489, 1.2%). Besides the 12 P-type IMGCs, 6 well and moderately differentiated type IMGCs contained some poorly differentiated components, totaling 18 IMGCs (86%) that were either mainly or partially P-type. Among the W-type IMGCs, the mean values of the Ki-67 and PCNA labeling indices (LI) for IMGCs with NI (Ki-67, 47.5%; PCNA, 58.3%) were higher than those of the 25 randomly selected IMGCs without NI (Ki-67, 39.2%; PCNA, 39.9%).

CONCLUSIONS

The potential for NI in IMGCs seems to be related closely to tumor size, the presence of poorly differentiated components, and, particularly in the W-type IMGC, the LI that are demonstrated immunohistochemically with Ki-67 and/or PCNA.