Pathology of Colorectal Polyps and Colorectal Cancer

Flashcards covering the pathology, classification, genetics, and staging of colorectal polyps and adenocarcinoma based on the lecture material.

Polyp

A lesion or mass projecting on the surface into the lumen composed of epithelium surrounding a core and attached to tissue of origin with a stalk.

Pedunculated Polyps

A type of polyp that possesses a stalk.

Sessile polyps

A type of polyp that lacks a stalk.

Inflammatory Polyps

Non-neoplastic polyps associated with solitary rectal ulcer syndrome, presenting with rectal bleeding, mucus discharge, and a location on the anterior rectal wall.

Hamartomatous Polyps

Disorganized, tumorlike growths composed of mature cell types normally present at the site at which the polyp develops.

Juvenile polyp

The most common hamartomatous polyp, typically occurring in children younger than $5$ years in the rectum; characterized by cystically dilated glands filled with mucus.

Hyperplastic (Metaplastic) Polyps

Sessile polyps with no malignant potential caused by defective epithelial cell turnover, leading to a "saw-tooth appearance" of overcrowded goblet cells.

Adenoma of the Colon

Benign but premalignant neoplastic lesions that can be solitary, multiple, sessile, or pedunculated, with epithelial dysplasia as a mandatory feature for diagnosis.

Epithelial dysplasia

The hallmark of colonic adenomas, characterized by nuclear hyperchromasia, pleomorphism, elongation, and stratification.

Tubular Adenoma

A microscopic type of adenoma where tubules are confined to the epithelial surface and core, lined by low-grade dysplastic epithelium.

Villous Adenoma

A large, cauliflower-like polyp with villi of fibrovascular core lined by dysplastic epithelium, carrying a higher risk for malignancy.

APC protein

A tumor suppressor gene product that normally leads to the destruction of $\beta$-catenin; its mutation or absence allows $\beta$-catenin to activate genes promoting the cell cycle.

$\beta$-catenin

An oncogene that, when accumulated in the nucleus, coactivates genes that promote the cell cycle in the WNT signaling pathway.

Microsatellite instability (MSI)

Also known as mismatch repair deficiency, it occurs when mismatch repair genes (like MSH2 or MLH1) are mutated, leading to uncorrected DNA replication errors.

Familial Adenomatous Polyposis (FAP)

An autosomal dominant disorder requiring at least $100$ colorectal adenomas for diagnosis, caused by APC gene mutation and resulting in $100\%$ cancer risk if untreated.

Hereditary nonpolyposis colorectal cancer (HNPCC)

Also known as Lynch syndrome, an autosomal dominant condition caused by germline mutations in mismatch repair genes, leading to right-sided colon cancers at young ages.

Proximal colon carcinoma

Tumors occurring in the cecum or ascending colon that grow as polypoid, exophytic masses and rarely cause obstruction.

Distal colon carcinoma

Annular lesions producing "napkin ring" constrictions and luminal narrowing, often leading to obstruction.

Desmoplastic reaction

The creation of fibrosis inside a tumor, typically seen in distal colon carcinomas causing wall thickening and constriction.

Grade

A pathologically determined classification based on how closely a tumor resembles its tissue of origin, such as well-differentiated or anaplastic.

Stage

The most important prognostic factor for colorectal cancer, determined by the TNM system to measure how far the tumor has spread.

Tis (Staging)

Carcinoma in situ or intramucosal carcinoma where the tumor involves the lamina propria but does not extend through the muscularis mucosae.

T1 (Staging)

The stage at which a tumor invades the submucosa.

T2 (Staging)

The stage at which a tumor invades the muscularis propria.

T3 (Staging)

The stage at which a tumor invades through the muscularis propria into pericolorectal tissues.

N1 (Staging)

The status indicating that one to three regional lymph nodes are positive for metastasis.

N2 (Staging)

The status indicating that four or more regional lymph nodes are positive for metastasis.

M1 (Staging)

The stage indicating metastasis to one or more distant sites, organs, or the peritoneum.