Prognostic significance of standardized AgNOR analysis and Ki-67 immunostaining in gastrointestinal stromal tumors

OBJECTIVE: To evaluate the prognostic utility of argyrophilic nucleolar organizer region (AgNOR) protein parameters and Ki-67-immunostained growth fraction (Ki-67 labelling index) and to correlate AgNORs with Ki-67 LI and the main clinicopathologic parameters in gastrointestinal stromal tumors (GISTs). STUDY DESIGN: On 55 patients with surgically excised GISTs, visualization and quantification of AgNORs were performed as specified in the guidelines of the Committee on AgNOR Quantification. RESULTS: AgNOR protein area (NORA) > or = 5.28 microns 2 was statistically associated with mitotic rate > or = 5 x 10 high-power fields (hpfs) (P < .001) and presence of necrosis (P < .001); Ki-67 LI > or = 9.69% was significantly associated with mitotic rate > or = 5 x 10 hpfs (P < .001), size > or = 5 cm (P = .033) and presence of necrosis (P < .001). Ki-67 LI and NORA strongly correlated. Preliminary Kaplan-Meier survival analysis showed that an increased value of NORA, Ki-67 LI, mitotic rate, tumor size and presence of necrosis had a negative influence on patient survival. Multivariate regression analysis showed that only NORA and Ki-67 LI were independent parameters in predicting the clinical outcome for patients with GISTs. Mitotic rate and necrosis remained as independent prognostic factors when NORA and Ki-67 LI were not allowed to enter in models. CONCLUSION: AgNOR protein quantity, as determined by image cytometry, and Ki-67 immunostaining seem to represent reliable predictive parameters in GISTs and are independent of mitotic rate, tumor dimension and necrosis.