Prognostic analysis of rectal stromal tumors by reference of National Institutes of Health risk categories and immunohistochemical studies.

Abstract

Prognostic analysis of stromal tumors focusing on the rectal area is rarely performed. This study elucidated prognostic factors by referencing biomarkers of Ki67 and p53. Forty-nine surgically resected rectal stromal tumors were collected from 1986 to 2006. Immunohistochemical studies were performed with antibodies of CD117, CD34, smooth muscle actin, desmin, S100, Ki67, and p53. The immunoreactivities were: CD34, 83.6 percent; smooth muscle actin, 28.5 percent; S100, 4.1 percent; desmin,16.3 percent;, Ki67, 30.6 percent;, and p53 34.7 percent. Both p53+ and Ki67+ tumors were associated with increased tumor mitosis, increased tumor size, nonspindle cell type, and increased cell pleomorphism (P < 0.05). Increased National Institutes of Health risk was associated with old age, nonspindle cell types, and severe nuclear pleomorphism (P < 0.05). Survival analysis demonstrated that older patients (P = 0.0039), large tumor size (P = 0.003), high mitotic count (P < 0.001), increased risk categories (P < 0.001), high cell pleomorphism (P = 0.003), p53+ (P = 0.007), and Ki67 + (P = 0.002) were prognostic factors for poor disease-free survival. An independent prognostic factor was tumor mitotic count. This study demonstrated the prognostic role of Ki67 and p53 in rectal stromal tumors. Notably, tumor mitosis was superior for prognostic prediction compared to National Institutes of Health risk categories.