001). Patients with tumors with less than five mitoses per 50 HPFs had a median survival time of 6.5 years, whereas those with more than five mitoses have a median survival of 2.9 years (p<0.001). For size <5 and >5 cm, the corresponding data were 7.4 and 3.4 years (p<0.001). Median survival time for tumor without atypia was 5.4 years, focal nuclear atypia, 2.5 years, and diffuse nuclear atypia, www.selleckchem.com/products/mek162.html 2.2 years (p<0.001). For patients with no identified coagulative necrosis, the median survival time was 4.4 years compared with 3.8 years for those with coagulative necrosis (p=0.006). In patients with ulceration, hemorrhage, and spindle or epithelioid cell types, there were no significant differences in overall survival. In a Cox univariate model, mean roundness (p<0.001), mean SL ratio (p=0.

017), and number of nuclei (p=0.043) were significant predictors of overall survival, whereas Feret diameter was not (p=0.94) (Figure 2). When tumors were stratified according to site, mean roundness was a significant predictor of overall survival both in the gastric (p=0.032) and small intestinal GISTs (p=0.047). Figure 2 Survival of patients with median roundness less than and more than 0.4061 (mean value). Mean roundness and nuclear SL ratio showed a strong correlation (0.919), and therefore, only one of these was used in multivariate Cox model calculations. Mean roundness was arbitrarily chosen. The result of the Cox proportional hazard analysis is presented in Table 3. The age at diagnosis was divided into decades, and the new values were used as continuous variables.

Location of primary tumor was divided into three categories: site other than stomach or small bowl, gastric location, or location in the small bowel, with values of 0, 1, or 2, respectively. These were used as categorical values. Size of tumor was likewise divided into three categories with unknown size, size <5 cm, and size >5 cm and used as categorical values. Mean roundness and number of nuclei were not independently significant in a model including sex, age at diagnosis, location of primary tumor, size, mitoses, nuclear atypia, coagulative necrosis, and hemorrhage. Table 3 Cox proportional hazard regression analysis with demographic, morphologic, and morphometric variables Discussion Number of mitoses and tumor size are currently regarded as the most helpful variables for evaluation of malignancy of GISTs, and the results of our study confirm their influence on overall survival in our series of 442 cases from Norway.

This supports the usefulness of the classification according to a consensus risk group stratification system based on maximum tumor size and mitotic count (Fletcher et al. Cilengitide 2002). Many techniques have been proposed for accurately predicting prognosis for GISTs. Chromosomal aberrations with loss of chromosomes 9 and 1 have been found to be quite specific for malignant GISTs (Debiec-Rychter et al. 2001).