Histopathological evaluation of response to neoadjuvant chemoradiotherapy in locally advanced rectal carcinoma

Preoperative neoadjuvant chemoradiotherapy (nCRT) followed by radical surgical resection is the mainstay of curative therapy in the management of patients with locally advanced (stage II and III) rectal carcinoma in order to reduce local recurrence and improve survival following surgery for rectal cancer. A brief survey of histopathological tumor regression grading (TRG) systems, other histomorphological and immunohistochemical findings and their clinical implications were reported including authors? experience. Possible diagnostic pitfalls are discussed specially on complete tumour regression (pCR), differentiation downstaging and downsizing and other aspects of standard histopathological examination and RT-induced histologic changes, including morphological, immunohistochemical and molecular transdifferentiation of tumour cells. Some of these histopathological parameters have to be considered when auditing rectal cancer resections and identifying prognostic factors