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Granulomatous inflammation appears to be part of a spectrum of sigmoid diverticulitis. In this setting, caution should be exercised to avoid an inappropriate diagnosis of Crohn's disease.

Macroscopic examination of large intestinal resection specimens by the surgical pathologist provides important diagnostic and prognostic information. This review summarises current recommended protocols and evidence based guidelines for gross description, dissection, and histological block selection in both neoplastic and non-neoplastic colorectal disease. Specific lesions discussed include colorectal cancer, polypectomies and polyposis syndromes, and inflammatory bowel disease. Microscopic examination is briefly described, with emphasis on certain pitfalls that might be encountered in routine practice. A section covering special techniques for the investigation of occult bleeding is included. (J Clin Pathol 2000;53:344-349) Keywords: large intestine; colorectal cancer; inflammatory bowel disease Large intestinal resections performed for neoplastic, vascular, and inflammatory disease form part of the everyday workload of many surgical histology laboratories. The importance of careful handling of colorectal cancer resections by the pathologist has received much attention recently.1 Identification of lymph node and resection margin involvement by adenocarcinoma is of paramount importance in determining whether patients will receive postoperative chemotherapy and/or radiotherapy.2 3 Macroscopic examination of the resection specimen also plays a major role in monitoring the quality of surgical practice. Gross examination of the large intestine in non-neoplastic conditions can also yield valuable diagnostic information, particularly in the classification of inflammatory bowel disease. Other conditions, such as angiodysplasia, require special preparation of the macroscopic specimen if the lesions are to be identified on subsequent microscopy.These guidelines aim to summarise current "good practice" recommendations for macroscopic examination and dissection of colorectal resections and polypectomy specimens, including the selection of appropriate blocks for histology. Details of microscopic examination and interpretation of biopsy specimens are beyond the remit of this paper; comprehensive guidelines for biopsy diagnosis of suspected inflammatory bowel disease have been published recently. 4 However, we have included a few guidelines relating to particular pitfalls in the histological assessment of large bowel lesions. Laboratory examination of large intestinal resections: general commentsResection specimens should be received fresh, unfixed, and unopened for optimum anatomical orientation. If the specimen is received outside laboratory hours, it can be refrigerated at 4°C overnight without risk of appreciable autolysis. Routine diagnostic immunocytochemistry and many molecular biological techniques can be applied to formalin fixed, routinely processed tissue, but receipt of fresh specimens also permits sampling for electron microscopy and research. Where receipt of fresh specimens is completely impractical, the theatre staV should be encouraged to send unopened specimens in an adequate volume of fixative-at...

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