Ki-67 expression in gastric cancer. Results from a prospective study with long-term follow-up

The characteristics of the cellular kinetic reflect the aggressiveness of the tumors and even their prognosis, many studies proving the correlation between the increased proliferation activity and a poor prognosis in a variety of neoplasms.

The analysis of immunohistochemical expression of the Ki-67 antigen using the monoclonal antibody MIB1 in 61 patients with gastric cancer, the correlation with clinicopathological factors and the prognosis of the patients.

We used the primary MIB1 antibody pre-diluted, using the LSAB technique, DAB visualization. The quantification of the reaction was performed by appreciating the marking index Ki-67 (MI Ki-67). Although all the lesions were positive, we noticed a marked intratumoral heterogeneity regarding the distribution of the Ki-67 score. The tumor cells were considered Ki-67 positive in the presence of brown nuclear staining of granular or diffuse type. The tumor invasion front has shown the most numerous Ki-67 positive cells.

In the gastric carcinomas, we remarked various Ki-67 scores. For a proper grouping of the results, we classified gastric carcinomas into two categories: carcinomas with high MI Ki-67 (≥45%) and carcinomas with low MI Ki-67 (≤45%). We noticed an increased frequency of high MI Ki-67 carcinomas in elderly patients (p=0.03) and also in the tumors developed at cardia level and those extended in the entire stomach in the moment of diagnosis (p<0.001). The histological forms associated to high Ki-67 values are represented by the anaplastic carcinoma (100% of cases) and papillary adenocarcinoma (60% of cases).We observed a close correlation between the degree of tumor differentiation and the Ki-67 score (p<0.001). The results of our study do not reveal any correlation between the Lauren's Classification of gastric carcinomas, the lymphovascular invasion, the depth of tumor invasion, the TNM stage and the Ki-67 score (p>0.05).

In our study, immunohistochemical assessment of the tumor proliferation does not represent a prognostic factor, but seems to be useful in identifying of a group of patients with aggressive tumors, needing adjuvant postoperatory chemotherapy.