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Genetics
Hereditary syndromes causing increased colorectal polyp formation include:

Familial adenomatous polyposis (FAP)
Hereditary nonpolyposis colorectal cancer
Peutz–Jeghers syndrome
Juvenile polyposis syndromeSeveral genes have been associated with polyposis, such as GREM1, MSH3, MLH3, NTHL1, RNF43 and RPS20. Familial adenomatous polyposis
Familial adenomatous polyposis (FAP) is a form of hereditary cancer syndrome involving the APC gene located on chromosome q521. The syndrome was first described in 1863 by Virchow on a 15-year-old boy with multiple polyps in his colon. The syndrome involves development of multiple polyps at an early age and those left untreated will all eventually develop cancer. The gene is expressed 100% in those with the mutation and it is autosomal dominant. 10% to 20% of patients have negative family history and acquire the syndrome from spontaneous germline mutation. The average age of newly diagnosed patient is 29 and the average age of newly discovered colorectal cancer is 39. It is recommended that those affected undergo colorectal cancer screening at younger age with treatment and prevention are surgical with removal of affected tissues. Hereditary nonpolyposis colorectal cancer (Lynch Syndrome)
Hereditary nonpolyposis colorectal cancer (HNPCC, also known as Lynch syndrome) is a hereditary colorectal cancer syndrome. It is the most common hereditary form of colorectal cancer in the United States and accounts for about 3% of all cases of cancer. It was first recognized by Alder S. Warthin in 1885 at the University of Michigan.
They can be either benign growths or malignant growths. The malignant growths can either have primary or secondary causes. Adenomatous polyps are considered precursors to cancer and cancer becomes invasive once malignant cells cross the muscularis mucosa and invade the cells below. Any cellular changes seen above the lamina propria are considered non-invasive and are labeled atypia or dysplasia. Any invasive carcinoma that has penetrated the muscularis mocos has the potential for lymph node metastasis and local recurrence which will require more aggressive and extensive resection. The Haggitts criteria is used for classification of polyps containing cancer and is based on the depth of penetration. The Haggitts criteria has level 0 through level 4, with all invasive carcinoma of sessile polyp variant by definition being classified as level 4. Level 0: Cancer does not penetrate through the muscularis mucosa. Level 1: Cancer penetrates through the muscularis mucosa and invades the submucosa below but is limited to the head of the polyp. Level 2: Cancer invades through with involvement of the neck of polyp. Level 3: Cancer invades through with involvement of any parts of the stalk. Level 4: Cancer invades through the submucosa below the stalk of the polyp but above the muscularis propria of the bowel wall. Adenomas
Neoplastic polyps of the bowel are often benign hence called adenomas. An adenoma is a tumor of glandular tissue, that has not (yet) gained the properties of cancer.The common adenomas of the colon (colorectal adenoma) are the tubular, tubulovillous, villous, and sessile serrated (SSA).