Reviewed 16 Nov. 2005

1) Clinico-pathologic Considerations

The diagnosis of colorectal cancer is based upon biopsy usually achieved at sigmoidoscopy or colonoscopy. It is particularly important that the clinician define the level at which the cancer is found, as this may have important bearing on subsequent surgical and adjuvant therapy. Any patient with a diagnosis of colorectal cancer should have a complete evaluation of the entire colon, preoperatively where possible, because of the increased risk of finding additional polyps or cancers.

2) Diagnostic Pathology

The vast majority of colorectal malignancies are adenocarcinomas. Rarer entities (carcinoid, etc) are dealt with in other sections of this manual. On occasion, therapy may be influenced by knowledge of the degree of differentiation present. The presence or absence of lymphatic and vascular invasion in the region of the tumour is increasingly thought to be of importance and may also ultimately contribute to the determination of the need for adjuvant therapy.

The histologic report will consist of examination of the fixed specimen and should include reporting of the cell type and degree of differentiation, the maximal depth of penetration of the bowel wall , the proximal and distal margins, the circumferential margins, involvement of lymphatics and blood vessels at the proximal, distal, and apical mesenteric margins, and examination and reporting on lymph nodes (preferably at least 6-12).

Non-lymph node deposits within the pericolic fat have the same prognostic significance as involved lymph nodes and these deposits are recorded as node deposits in the staging of the primary cancer. Patients in whose specimens no lymph nodes are identified have a higher recurrence risk than those with no involved nodes, probably by virtue of understaging.