Purpose: 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.
Methods: 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.
Results: 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.
Conclusions: 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.