Risk Stratification of Gastrointestinal Stromal Tumors: Are Imaging Findings and Histopathological Features Correlated?

Ki-67 is a tumor proliferation marker for tumor staging and poorly differentiated malignancies. The aim was to compare qualitative and quantitative Computed Tomography (CT) findings with the Ki67 index to predict pre-op malignancy potential. Forty-five patients with GIST were confirmed histopathologically and underwent enhanced CT examination from 2012-2022. According to Miettinen and Lasota's classification, all tumors were classified as very low, low, moderate, or high. Location, size, shape, contour, growth pattern, necrosis, tumor mean density on the portal venous images, calcification, and intratumoral marked vascular findings were evaluated. Density (Hounsfield unit-HU) values were calculated in portal venous phase images, lesion/abdominal aorta (L/A.9, and paraspinal muscle (L/P) density ratios. GISTs were divided into three Ki67 groups of < 4%, 4-15%, and > 15%. CT findings were compared according to the mitotic index in the Miettinen classification and the Ki67 index. Ten (22.2%) tumors were very low, 9 (20%) low, 7 (15.6%) moderate, and 19 (42.2%) high malignancy potential. There was a significant correlation between the mitotic index and Ki67 index values (p < 0.001, r = 0.596). The most statistically significant cut-off value of Ki67 was 4% for differentiating tumors with poor prognosis indicators. The CT findings revealed statistically significant differences in size, density, and L/A and L/P ratios between the Ki67 groups (p < 0.03). Size, Lesion/Abdominal aorta, and Lesion/Paraspinal muscle HU ratios were highly correlated with high Ki67 index values, a valuable determinant of risk stratification.