| Disease | Age of onset | Gene | Mode of inheritance | # Polyps | Polyps distribution | Histology |
| Non-neoplastic polyps | ||||||
| Inflammatory “cap” polyposis | 40 - 50 | - | Sporadic | 1 to >100 | Predominantly in distal colon, but can be throughout the colon | Hyperplastic crypts, inflammatory infiltrate and fibromuscular obliteration of the lamina propria, with a white cap of fibrinopurulent exudate |
| Hyperplastic polyposis | >40 | - | Familial cluster | 5 - 100, mostly 40 - 100 | Abundance throughout the colon, sparing of stomach or small bowel | Hyperplastic polyps, sessile serrated adenomas |
| Adenomatous polyposis | ||||||
| Classical Familial adenomatous polyposis (FAP) | 10 - 20 | APC | AD | >100 | Colorectum (100%), gastric fundic gland polyps, duodenum, and periampullary polyps | Adenoma ( tubular adenomas identical to sporadic adenomas) |
| Attenuated FAP (AFAP) | 20 - 30 | APC | AD | <100 | Colorectum, Gastroduodenum and periampullary polyps | Adenoma (same as FAP) |
| MUTYH- associated polyposis (MAP) | 40 - 60 | MUTYH | AR | 20 - 100 | Colorectum Gastric and duodenal polyps | Adenoma (tubular adenomas, with a minority of tubulovillous adenomas and few hyperplastic polyps) |
| Hamartomatous polyposis | ||||||
| Juvenile polyposis syndrome | <20 | SMAD4, BMPR1A, ENG | AD | 5 to 200 | More common in the colorectum. The chance in the stomach and small intestine are <20% | Mucous-filled, edematous stroma, dilated glands, inflammatory cell infiltration, and absence of smooth-muscle proliferation |
| Peutz-Jeghers syndrome | 10 - 30 | STK11 gene | AD | 1 - 20 | Most common in small intestine (100%), less common in colorectum and stomach (20%). Also seen extra-intestinal tract such as respiratory, uterus, or bladder | “Christmas tree” appearance at low power, Hamartomatous polyps supported by broad bands of muscularis mucosa smooth muscle |
| Cowden syndrome | 9 - 20 | PTEN | AD | Multiple | Throughout the GI tract | Hamartomatous polyps, histologically, similar to the juvenile polyps, frequently containing ganglion cells |
| Bannayan- Ruvalcaba- Riley syndrome | Early in life | PTEN | AD | Multiple | Majority are identified in the distal ileum and colon, though they may be seen throughout the GI tract | Hamartomatous polyps, histologically similar to the JPS-type polyp |
| Cronkhite- Canada syndrome | 50 - 60 | -- | Sporadic | 5 to numerous | Predominantly in stomach and colon (90%), followed by small bowel (80%) and rectum (67%), usually spare esophagus | Hamartomatous polps exhibiting glandular hyperplasia, cystic dilation, mucosal edema |