Proliferative activity of micrometastases in the lymph nodes of patients with gastric cancer.

Background: Immunohistochemically detectable isolated tumour clusters (ITCs) with a diameter of less than 0.2 mm have been regarded as non-metastatic lesions, because of a lack of proliferative activity. This study investigated the proliferative activities of ITCs.

Methods: Three hundred and eight patients with primary gastric cancer diagnosed as pN0 by routine histological examination were studied. All patients underwent curative resection. Sections of lymph nodes were stained by double-immunostaining methods using anti-cytokeratin and anti-Ki-67 antibody (MIB-1).

Results: ITCs were detected in 77 nodes from 37 patients, designated as having pN0(i+) lesions. Seventy of 77 lymph nodes with ITCs were detected in the N1 station, and seven were found in the N2 station. Of 25 single isolated cancer cells, 12 showed positive labelling with MIB-1, and 49 of 52 ITCs with clusters of cancer cells had positive MIB-1 labelling (mean(s.d.) 46.6(30.1) per cent). Five of the 37 patients with ITCs (pN0(i+)) versus one of the 271 patients with no evidence of ITCs (pN0(i-)) died from recurrence. Patients with ITCs had a significantly worse prognosis than those without (P = 0.014).

Conclusions: ITCs have a high proliferative activity and may have the potential to evolve into established lymph node metastasis.