Gastrointestinal stromal tumors of the rectum: Clinical, pathologic, immunohistochemical characteristics and prognostic analysis

Objective. To describe the clinical, pathological and immunohistochemical characteristics of rectal gastrointestinal stromal tumors ( GISTs) and to correlate them with clinical outcomes. Material and methods. A retrospective review of 29 patients with surgically treated rectal GISTs during the period from 1997 to 2005 was undertaken. The NIH ( National Institute of Health Consensus) criteria were applied. Results. All the rectal GISTs in our series originated in the lower half of the rectum and patients underwent primary surgery for complete resections; High-risk, intermediate-risk, low-risk and very low-risk GISTs were found in 11, 6, 5 and 7 patients, respectively. Necrosis, adjacent ( mucosal or serosa) invasion and marked pleomorphisms were found in 10, 7 and 20 patients, respectively. Positive expression of CD117, CD34, SMA and S-100 was found in 28, 28, 7 and 3 patients, respectively. Twelve patients had recurrence or metastasis within the median disease-free survival time of 41 months. Among the patients who underwent local resections, the recurrence rate for low-risk and very low-risk GISTs was only 1/10; for intermediate-risk and high-risk GISTs, the recurrence rate after local resections was 3/4, which was higher than the recurrence and metastasis rate of 8/13 after laparotomy. Of the 12 patients with adverse outcomes, 4 patients underwent secondary complete resections; however, all 4 patients had further recurrences. On univariate analysis, risk classification ( p = 0.0002), necrosis ( p = 0.0205), adjacent invasion ( p = 0.0090) and marked pleomorphism ( p = 0.0480) were significant predictors of disease-free survival. In the Cox regression model, only the risk classification ( p = 0.012) was found to be an independent factor. Conclusions. We found that rectal GISTs arise predominantly in the lower half of the rectum and have high CD117 and CD34 expression. Local resection may be a good choice for very-low-risk and low-risk GISTs, but aggressive surgery may be more beneficial for high-risk and intermediate-risk GISTs. For patients with disease recurrence, the results of secondary surgery were poor. Only the NIH risk classification proved to be an independent prognostic factor for rectal GISTs, whereas the proof for other factors was insufficient.