Rectal gastrointestinal stromal tumor: a clinical and pathologic analysis

Abstract

To investigate the clinicopathologic characteristics and therapy of rectal gastrointestinal stromal tumors (GISTs). Clinical findings, morphologic features, immunophenotype and prognosis of 53 cases (58 samples) of rectal GISTs were investigated. Thirty-three patients were male and 20 were female. The age of patients ranged from 19 to 81 years, with an average of 49.7 years. The main symptoms included rectal disorders in 29 patients and vaginal mass in 2 patients, while the tumors in 22 patients were found by routine physical examination. Thirty-five primary GISTs were resected completely without preoperative therapy, and thirteen tumors were resected after therapy of imatinib. Five tumors were recurrent. Imatinib therapy in 13 patients led to smaller and softer tumor mass grossly and decreased cellularity and marked degeneration histologically. Of the 35 primary rectal GISTs, there were 17 (48.6%), 6 (17.1%), 0(0), and 12 (34.3%) cases diagnosed as very low risk, low risk, medium risk, and high risk respectively. Eight cases had tumor of 1 cm or less in diameter. In the five recurrent cases, the tumors showed increased cellularity, mitotic figures, and Ki-67 index. Imatinib therapy led to smaller and softer tumor mass grossly and decreased cellularity and marked degeneration histologically. Immunohistochemical stains showed CD117, DOG1, and CD34 positivity, S-100 protein negativity and indefinite SMA stain. Rectal GISTs are rare tumors with a male predominance.Patients without obvious sypmtoms are found by themselves and by routine physical examination. The tumor diameter less than 2 cm is common while larger than 5 cm is few. Diagnosis of rectal GISTs is easily made by biopsy and patients often acquire preoperative therapy for preserving anal sphincter function.