Health

What are the most common primary tumor sites that can show colon metastases?  These include lung, stomach, breast, ovary, endometrium, and melanoma. These tumor cells creep under the surface epithelium or form submucosal nodules of varying sizes.More than one focus is generally seen.The surface epithelium lacks dysplasia (expected with primary colon adenocarcinomas). IHC may be …

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How are neuroendocrine tumors classified?  The spectrum ranges from well-differentiated neuroendocrine tumors (carcinoid tumors) to poorly differentiated (small cell carcinomas) and large cell neuroendocrine carcinomas. The common site of involvement is the rectum, followed by the cecum and sigmoid colon. The histologic characteristics are similar to those described in the small intestine section. These are …

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Adenomatous polyp syndromes FAP affects the entire colon and rectum; there is 100% risk of cancer. Histologically, tubular adenomas and occasionally tubulovillous and villous adenomas are identified. The variants include attenuated FAP, Gardner syndrome, Turcot syndrome, hereditary flat adenoma syndrome, and Muir-Torre syndrome. All are hereditary syndromes.

Hamartomatous polyp syndromes Hamartomatous polyps include juvenile hamartomatous polyp and the hamartomatous polyp of Peutz-Jeghers type. Peutz-Jeghers syndrome involves the entire GI tract (small intestine most common); there is a 93% lifetime risk of cancer. Sporadic Peutz-Jeghers polyps can occur but are extremely rare. Follow-up of these patients is warranted. Histologically, these typically show arborizing smooth muscle …

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What is the abnormality in MSI unstable sporadic CRCs?  These constitute approximately 12% to 15% of CRCs. The MSI-H is caused by somatic inactivation of hMLH1 mismatch repair gene due to hypermethylation of the promoter region preceding the gene sequence, whereas in HNPCC, the instability is due to germline mutation in the MMR genes. Most of the sporadic ones …

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What histologic features seen in CRCs can predict MSI H?  These tumors are usually right sided, show a medullary or syncytial growth pattern, have mucinous or signet ring cell features, are poorly differentiated, and show lymphocytic infiltration. Also, a Crohn-like reaction (nodular lymphoid aggregates) is seen beyond the advancing edge of the tumor. These features, …

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What genetic abnormalities point to HNPCC?  HNPCC presents in a younger age group and has an autosomal dominant pattern of inheritance. Revised Bethesda Criteria are set to screen the patients for MSI. DNA mismatch repair (MMR) gene defect is tested for hMLH1 (50%), hMSH2 (39%), hMSH6 (8%), and hPMS2 (1%) genes. These defects result in insertion or deletion of nucleotides in the microsatellite sequences, which …

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