Abstract

Neoadjuvant chemoradiation (NACR) is now standard of care in stage II and III rectal cancer. The advent of this modality of treatment has impacted on the way the pathological evaluation of resection specimens that have been subjected to preoperative chemoradiation is conducted. The gross description, sectioning and microscopic examination have had to be adapted to accommodate the changes induced by NACR. Attempts at introducing a uniform approach to the gross triaging and reporting of these specimens have been met with muted response. There still exists much variation in approach. The purpose of this overview is to highlight some of the newer developments and issues around NACR-treated rectal cancers from a pathological point of view. The NACR-treated resection specimens should be handled in a consistent manner, at least within individual institutions, if not universally. There should be generous sampling with multiple sections taken as tumour is often sequestered deep in the bowel wall. Microscopic examination should be extra vigilant as residual cancer can be present as single cells or small clusters, often deep in the muscularis propria or serosa. Acellular pools of mucin or non-viable tumour cells in mucin within the bowel wall or lymph nodes are not regarded as positive and do not upstage the tumour. The issue of grading of regression has been the subject of much debate, and several approaches have been published. It is recommended that a system that has clinical meaning and use to oncologists be used. Lymph node counts will be reduced after NACR, but reasonable attempts to accrue 12 nodes should be made.