[Histopathologic examination of rectal carcinoma]

In patients with rectal carcinoma, the histopathological evaluation of the surgical specimen provides pivotal prognostic and therapeutic information. Important parameters are tumor site, depth of invasion, histological type and grade, pattern of invasion (diffusely infiltrating versus expanding margin), degree of peritumoral lymphocytic infiltration, and tumor involvement of surgical margins and lymph nodes. Evaluation of the circumferential (deep, lateral) margin is of utmost importance. It should be labeled with ink in the gross specimen and should be examined histologically using several tissue blocks. The number of lymph node metastases and the total number of lymph nodes examined should be reported. A histological evaluation of the distal mesorectum in its entirety is recommended to detect discontinuous distal mesorectal tumor spread. The histopathological findings should be summarized using the TNM-classification.