236 Journal of the College of Physicians and Surgeons Pakistan 2014, Vol. 24 (4): 236-240 INTRODUCTION Colorectal cancer is the third most common cancer worldwide. 1 In United States it is the second leading cause of death. 2 The incidences of colorectal cancers has been increasing in South East Asia specially Pakistan for the last decade. In Pakistan, colorectal cancers constitute 25.4% of gastrointestinal malig- nancies in males and 20.1% of gastrointestinal malignancies in females. 3 According to cancer registry of Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, colorectal cancer is among top four malignancies. 4,5 About 40 - 50% of large bowel cancers occur in rectum. Adenocarcinomas are most frequent comprising approximately 98% of rectal cancers. 1,6 Patients with rectal cancer can present with bleeding per rectum, weight loss, abdominal pain and obstructive symptoms. As a first step of clinical management, colonoscopy is carried out. In case of visible tumour or suspicious area, biopsy is performed and biopsy material is sent for histopathological examination. If malignancy is confirmed by histopathology, pre- operative radiological investigations are performed to determine the stage and extent of disease. Various radiological modalities are available for this purpose; these include Magnetic Resonance Imaging (MRI), Computed Tomography (CT) and Endorectal Ultra- sound (ERUS). MRI is considered more sensitive and specific to determine tumour relation to mesorectal fascia. Radiological investigation provides information regarding tumour size, lymph node status, any metastatic deposit and distance of tumour from mesorectal fascia. 6,7 The most important factor influencing prognosis is complete mesorectum removal (circumferential margin status). 8 Complete mesorectal removal is also known as Total Mesorectal Excision (TME). Another very important factor which determines clinical outcome of rectal cancers is the distance of tumour from mesorectal fascia; incidences of local recurrence increases as tumour reaches closer to the circumferential margin. 9,10 When comparison between radiological and patho- logical finding is done, radiological findings show discordant results to histopathological findings. 1,7,9 Accuracy of MRI of predicting mesorectal fascia status (circumferential margin) is 76% with sensitivity and specificity of 96.9% and 73.8% respectively. 11,12 ORIGINAL ARTICLE Comparing Histopathological and Magnetic Resonance Imaging Based Mesorectal Fascia Status in Patients with Rectal Carcinoma Usman Hassan, Rizwanullah Khan and Muhammad Tariq Mehmood ABSTRACT Objective: To compare mesorectal fascia status on histopathological findings with MRI based radiological mesorectal fascia status in patients with rectal carcinoma taking histopathology finding as gold standard. Study Design: Analytical study. Place and Duration of Study: Department of Pathology, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, from January 2011 to April 2012. Methodology: Biopsy proven cases of rectal adenocarcinoma undergoing abdominoperineal resection were included in this study. Microscopic examination of slides was done to determine mesorectal fascia status as involved or otherwise without knowing the results of mesorectal fascia status on MRI. Mesorectal fascia status of MRI was determined by a radiologist who was not aware of the histopathological assessment of mesorectal fascia. Mean and standard deviation was calculated for age. Frequency and percentage were calculated for gender and mesorectal fascia status. 2 x 2 table was generated to calculate sensitivity, specificity, positive predictive value and negative predictive values and diagnostic accuracy of MRI for mesorectal fascia involvement taking histopathology as gold standard. Results: The sensitivity of MRI to detect mesorectal fascia involvement was 23.07% and specificity was 70.5%. Positive predictive value of MRI was 10% and negative predictive value was 54.54%. Diagnostic accuracy of MRI for mesorectal fascia involvement was calculated as 50%. Conclusion: MRI findings regarding mesorectal fascia status as involved or otherwise are not helpful when compared with histopathological findings which is the gold standard. Key Words: Mesorectal fascia. Rectal adenocarcinoma. Total mesorectal excision. Magnetic resonance imaging. Histopathology. Department of Pathology, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore. Correspondence: Dr. Usman Hassan, House No. 356, Street 4, Phase 4, Gulraiz Housing Scheme, Rawalpindi. E-mail: drusmanhassan256@gmail.com Received: February 02, 2013; Accepted: October 23, 2013.