Prevalence and Clinical Significance of Acellular Mucin in Locally Advanced Rectal Cancer Patients Showing Pathologic Complete Response to Preoperative ChemoradiotherapyLim, Seok-Byung MD*; Hong, Seung-Mo MD†; Yu, Chang Sik MD*; Hong, Yong Sang MD‡; Kim, Tae Won MD‡; Park, Jin-hong MD§; Kim, Jong Hoon MD§; Kim, Jin Cheon MD*The American Journal of Surgical Pathology: January 2013 - Volume 37 - Issue 1 - p 47–52 doi: 10.1097/PAS.0b013e3182657186 Original Articles Abstract Author Information Occasionally, patients with locally advanced rectal adenocarcinoma who receive preoperative chemoradiotherapy (CRT) show acellular mucin in resection specimens that had shown pathologic complete response (pCR), but the clinical and prognostic significance of this finding has been controversial. This study analyzed data from 217 consecutive patients showing pCR to preoperative CRT followed by resection to evaluate the clinicopathologic features and prognostic significance of acellular mucin. Patients were categorized according to the presence of acellular mucin, as identified by pathologic analysis. The clinicopathologic findings and oncologic results were compared. Acellular mucins were identified in 35 (16.1%) of 217 pCR patients. Acellular mucins were found predominantly in male patients (20.8% vs. 9.8%, P=0.039) and in those with mucinous/signet ring cell differentiation (66.7% vs. 15.1%, P=0.008). The presence of acellular mucin was more frequent in patients with a shorter (<42 d) CRT-operation interval (22.6% vs. 10.3%, P=0.017). With a mean follow-up of 41 months (range, 2 to 119 mo), the 3-year overall survival (96.8% with mucin vs. 95.9% without mucin, P=0.314) and the 3-year disease-free survival (97.0% with mucin vs. 93.0% without mucin, P=0.131) did not differ between the groups. The presence of acellular mucin in rectal cancer patients showing pCR to preoperative CRT is associated with male sex and mucinous differentiation and does not have a significant impact on oncologic outcomes. Acellular mucins are also associated with the CRT-operation interval as a phenomenon of time-dependent response to CRT. Departments of *Surgery †Pathology ‡Oncology §Radiation Oncology, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Seok-Byung Lim, MD, Department of Colon and Rectal Surgery, University of Ulsan College of Medicine and Asan Medical Center, Asanbyeongwon-gil 86, Songpa-gu, Seoul 138-736, Korea (e-mail: email@example.com). © 2013 Lippincott Williams & Wilkins, Inc.