Histopathology of Colorectal Cancer after Neoadjuvant Chemoradiation Therapy

Neoadjuvant treatment has become the standard of care for locally advanced gastrointestinal carcinoma, hence, the pathologist increasingly encounters treated primary and metastatic colorectal tumors. The pathologic assessment of therapeutic response and evaluation of residual disease is important because the histologic response to therapy or tumor response grade (TRG) has been shown to correlate with survival. Therefore, it is important for the pathologist to be familiar with the changes seen in colorectal cancer and metastatic colorectal cancer after neoadjuvant therapy. This review discusses the treatment effects seen in colon, rectal and liver resections including lymph nodes and the evaluation of residual tumor tissue in these specimens.