Colon Colonic polyps are usually epithelial, and are acquired or hereditary
Acquired polyps Adenomatous (tubular or villous) in morphology, ↑ frequency with age; although often asymptomatic, larger polyps are often announced by bleeding, or changed bowel habits; if really large, APs may form a leading 'front' of an intussusception; distinction between adenomatous polyps ('tight' round glands) and villous adenomas (finger-like fronds of elongated glands) has little practical importance–both have malignant potential; periodic colonoscopy and polypectomy yields a 3-fold ↓ in subsequent cancer; hyperplastic polyps are also acquired but are non-neoplastic
Hereditary polyps are epithelial and may overlap with each other
• Familial adenomatous polyposis (FAP) A premalignant, AD MIM 175100 condition presenting in early adulthood with 100s to 1000s of colonic polyps, related to a loss of the normal repression of DNA synthesis in the entire colonic epithelium; adenocarcinoma occurs in 70–100% of Pts, prevented by prophylactic colectomy
• Gardner syndrome A rare AD MIM 175100 condition with premalignant polyps of the entire GI tract, which is identical to FAP, but has, in addition, extraintestinal tumors; most Pts develop colon carcinoma; other neoplasms in GS Pts include bile duct carcinoma, osteomas of the mandible, skull, and long bones, soft tissue tumors (fibromas, lipomas), sebaceous cysts, and rarely, thyroid and adrenal gland cancers
• Turcott syndrome A rare AR MIM 276300 condition associated with brain tumors, eg medulloblastoma, glioblastoma
• Other colon polyps Hamartomas, hyperplastic polyps, juvenile and retention polyps–little neoplastic potential
• Turcott syndrome A non-hereditary condition characterized by diffuse GI polyposis, accompanied by alopecia, nail atrophy, cutaneous hyperpigmentation, weight loss, protein-losing enteropathy, electrolyte imbalance and malnutrition
• Peutz-Jeghers syndrome An AD MIM 175200 condition with hamartomas of the entire GI tract, predominantly of the small intestine, focal Paneth cell hyperplasia, melanin spots in buccal mucosa, lips, and digits, intussusception and bleeding; colonic adenocarcinomas, when seen in PJS, arise in adenomatous and not in hamartomatous polyps; PJS may be associated with Sertoli cell tumor with annular tubules, see SCTAT.
Female urogenital tract Endometrial and endocervical polyps are circumscribed foci of cystic glandular hyperplasia of the mucosa and may cause abnormal bleeding; carcinoma arising in such polyps is rare; when smooth muscle is also present, they are designated as adenomatous polyps DiffDx Polypoid smooth muscle tumors, benign and malignant. See Müllerian mixed tumor.
Nasopharynx Nasal polyps Inflammatory ('allergic') polyps of the nasal cavity are not neoplastic, but rather reactive to inflammation or allergy; unlike true polyps, nasal polyps display edema and chronic inflammation (eosinophils, plasma cells, and lymphocytes), are bilateral, recurrent, and intranasal
Skin Squamous polyps and fibroepithelial polyps or 'skin tags' are benign prolapses of upper dermis onto the skin surface, which have no neoplastic potential
Stomach polyp Gastric polyp It is often (incorrectly) assumed that colon polyps are analogous to gastric polyps; hyperplastic polyps (type I and II polyps by Japanese authors) comprise 75% of all gastric polyps; they are neoplastic, but are usually benign