Prognostic value of histomorphological and immunohistochemical parameters in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) exhibit heterogeneous biological behavior, ranging from indolent lesions to aggressive malignancies, making accurate prognostic assessment essential. Prognosis is commonly determined using tumor size, mitotic count, and anatomical location; however, additional histopathological parameters may provide further prognostic insight. In this retrospective study, 40 GIST cases were evaluated to investigate the prognostic significance of histomorphological and immunohistochemical features. Tumors were classified into prognostic risk groups according to the Miettinen classification and categorized as low/very low risk or intermediate/high risk. Histomorphological parameters, including growth pattern, presence of necrosis, cellular atypia, and cell morphology, were assessed, along with immunohistochemical expression of Ki-67, CD34, smooth muscle actin, desmin, and S-100. Intermediate- and high-risk tumors were significantly associated with infiltrative growth pattern, tumor necrosis, and moderate-to-severe cellular atypia compared with low-risk tumors (p<0.05). The Ki-67 proliferation index was also significantly higher in the intermediate/high-risk group (p<0.001). No statistically significant associations were observed between prognostic risk groups and CD34, smooth muscle actin, desmin, or S-100 expression. These findings indicate that histomorphological features, such as necrosis, growth pattern, and cellular atypia, together with the Ki-67 proliferation index, may serve as valuable adjunctive prognostic markers in GISTs, complementing conventional risk stratification systems.