Fig. 15.38 Colorectalcarcinoma.(A)Endoscopicviewofulceratedascendingcolonadenocarcinoma.(B)Circumferential,ulceratedrectalcancer.Notetheanalmucosaatthebottomoftheimage.(C)Cancerofthesigmoidcolonthathasinvadedthroughthemuscularispropriaandispresentwithinsubserosaladiposetissue(left). Areasofchalkynecrosisarepresentwithinthecolonwall(arrow). (Endoscopic image courtesy of Dr. Ira Hanan,The University of Chicago, Chicago, Illinois.) presence or absence of lymph node metastases. These factors were originally recognized by Dukes and Kirklin and form the core of the TNM (tumor-node-metastasis) classification and staging system from the American Joint Committee on Cancer. Staging systems have become more complex with time, reflecting more nuanced treatment approaches and personalized therapeutic strategies. The most important distinctions are:
Depth of invasion. Tumors limited to the submucosa (i.e., those that do not cross the muscularis mucosae) have 5-year survival rates approaching 100%, while invasion into the submucosa or muscularis propria reduces 5-year survival to 95% and 70% to 90%, respectively (for tumors limited to the primary site). Invasion through the visceral serosal surface or into adjacent organs and tissues reduces survival further.
The presence of lymph node metastases (
Fig. 15.40A ) further compromises survival. As a result, most cases with lymph node metastases receive radiation or chemotherapy. In some cases, these treatments may be administered prior to primary tumor resection, a process termed neoadjuvant therapy. Molecular characterization of the tumor can be helpful in guiding the specific therapeutic approach.
• Distant metastases to lung (
Fig. 15.40B ), liver (
Fig. 15.40C ), or other sites also limits survival, and only 15% or fewer of patients with tumors at this stage are alive 5 years after diagnosis. Because of the portal drainage, the liver is the most common site of metastatic lesions. However, the rectum does not drain by way of the portal circulation, and metastases from carcinomas of the anorectum region often circumvent the liver.
Regardless of stage, however, some patients with small numbers of metastases do well for years after resection of distant tumor nodules. This is particularly true of metastases to liver or lung and emphasizes the clinical and molecular heterogeneity of colorectal carcinomas.
Fig. 15.39 Histologicappearanceofcolorectalcarcinoma.(A)Well-differentiatedadenocarcinoma.Notetheelongated,hyperchromaticnuclei.Necroticdebris,presentintheglandlumen,istypical.(B)Poorlydifferentiatedadenocarcinomaformsafewglandsbutislargelycomposedofinfiltratingnestsoftumorcells.(C)Mucinousadenocarcinomawithsignetringcellsandextracellularmucinpools.
http://ebooksmedicine.net
Fig. 15.40 Metastaticcolorectalcarcinoma.(A)Lymphnodemetastasis.Notetheglandularstructureswithinthesubcapsularsinus.(B)Solitarysubpleuralnoduleofcolorectalcarcinomametastatictothelung.(C)Livercontainingtwolargeandmanysmallermetastases.Notethecentralnecrosiswithinmetastases.
COLONICPOLYPS,ADENOMAS,ANDADENOCARCINOMAS
Intestinal polyps canbeclassifiedasnonneoplastic orneoplastic. Thenonneoplasticpolypscanbefurtherdefinedasinflammatory, hamartomatous, orhyperplastic.
Inflammatory polyps formasaresultofchroniccyclesofinjuryandhealing.