The colorectal adenoma is a benign

glandular tumor A gland is a cell or an organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also function to remove unwanted substances ...

of the colon and the rectum. It is a precursor lesion of the colorectal adenocarcinoma (

colon cancer Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel ...

). They often manifest as

colorectal polyp A colorectal polyp is a polyp (fleshy growth) occurring on the lining of the colon or rectum. Untreated colorectal polyps can develop into colorectal cancer. Colorectal polyps are often classified by their behaviour (i.e. benign vs. malignant) ...

Comparison table

Pie chart of colorectal polyp etiologies

Tubular adenoma

In contrast to

hyperplastic polyps A hyperplastic polyp is a type of gastric polyp or colorectal polyp. Cancer risk Most hyperplastic polyps are found in the distal colon and rectum. They have no malignant potential, which means that they are no more likely than normal tissu ...

, these display dysplasia.

Tubulovillous adenoma

''Tubulovillous adenoma'', ''TVA'' are considered to have a higher risk of becoming

malignant Malignancy () is the tendency of a medical condition to become progressively worse; the term is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous benign tumor, ''benign'' tumor in that a malig ...

(

cancerous Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

) than tubular adenomas. File:Non-proliferative versus proliferative colonic crypts.jpg, Normal (left) versus dysplastic (large at right) colonic crypts, the latter conferring a diagnosis of a tubular and/or villous adenoma. File:Histopathology of high-grade dysplasia in tubulovillous adenoma, annotated.png, Histopathology of high-grade dysplasia in a tubulovillous adenoma, in this case seen mainly as loss of cell polarity, as cells become more plump and haphazard than the elongated and parallel nuclei of surrounding low-grade dysplasia.

Villous adenoma

These

adenomas An adenoma is a benign tumor of epithelial tissue with glandular origin, glandular characteristics, or both. Adenomas can grow from many glandular organs, including the adrenal glands, pituitary gland, thyroid, prostate, and others. Some adenomas ...

may become

(

). Villous adenomas have been demonstrated to contain malignant portions in about 15–25% of cases, approaching 40% in those over 4 cm in diameter. Colonic resection may be required for large lesions. These can also lead to secretory diarrhea with large volume liquid stools with few formed elements. They are commonly described as secreting large amounts of mucus, resulting in

hypokalaemia Hypokalemia is a low level of potassium (K+) in the blood serum. Mild low potassium does not typically cause symptoms. Symptoms may include feeling tired, leg cramps, weakness, and constipation. Low potassium also increases the risk of an ...

in patients. On endoscopy, a "cauliflower' like mass is described due to villi stretching. Being an adenoma, the mass is covered in

columnar epithelial cell Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of many ...

Sessile serrated adenoma

Sessile serrated adenoma A sessile serrated lesion (SSL) is a premalignant flat (or sessile) lesion of the colon, predominantly seen in the cecum and ascending colon. SSLs are thought to lead to colorectal cancer through the (alternate) ''serrated pathway''. This diffe ...

s are characterized by (1) basal dilation of the crypts, (2) basal crypt serration, (3) crypts that run horizontal to the basement membrane (horizontal crypts), and (4) crypt branching. The most common of these features is basal dilation of the crypts.

References