Colorectal adenomatous polyps are neoplastic polyps originating from glandular epithelium of colon and rectal mucosa. They are considered premalignant lesions in the adenoma-carcinoma sequence. Found in 25-30% of the general population with incidence increasing with age. Classified as low and high-grade dysplasia. Size (>10 mm), villous histology, and high-grade dysplasia increase malignant transformation risk. CT colonography and colonoscopy are primary diagnostic modalities.
Age Range
40-80
Peak Age
60
Gender
Male predominant
Prevalence
Common
Adenomatous polyps are clonal neoplastic proliferations originating from glandular epithelium of the colonic mucosa. Inactivation of the APC tumor suppressor gene (overactivation of Wnt signaling pathway) is the initiating event — beta-catenin accumulation increases cell proliferation. Polyps grow from mucosa into the lumen and show pedunculated (stalked) or sessile (broad-based) morphology. Histologically, they form glandular structures in tubular (80%), villous (5%), or tubulovillous (15%) patterns. Malignancy risk increases with villous component because villous structures carry more surface area and genomic instability. On CT, polyps appear as intraluminal soft tissue density protrusions — enhancement reflects tumor neovascularization. CT colonography reliably detects polyps >6 mm; clinical significance of <6 mm polyps is debated.
Polypoid protrusion of soft tissue density showing enhancement in the air-surrounded colon lumen on CT colonography. Enhancement presence is the basis for differentiation from fecal residue. This appearance is the signature finding of adenomatous polyp and indicates colonoscopic polypectomy.
Intraluminal polypoid lesion of soft tissue density on CT colonography. Shows homogeneous enhancement. Stalk may be visible in pedunculated type. Sessile type sits on wall with broad base.
Report Sentence
An intraluminal polypoid lesion measuring approximately ___ mm is seen in the ___ segment, consistent with adenomatous polyp; colonoscopic evaluation is recommended.
Homogeneous enhancement — reflects the regular vascular architecture of adenomatous polyp. Internal necrosis or calcification is not expected. Enhancement presence is critical for polyp-fecal residue differentiation.
Report Sentence
The lesion shows homogeneous enhancement on contrast-enhanced series, consistent with a true polyp.
Intraluminal protrusion of soft tissue density (30-60 HU) on non-contrast CT. Polyp profile surrounded by air is clearly visible. No calcification.
Report Sentence
An intraluminal protrusion of soft tissue density is seen in the ___ segment, consistent with a polyp.
Stalk structure in pedunculated polyps — thin vascular pedicle connects polyp head to wall base. Stalk appears as linear soft tissue band on CT.
Report Sentence
The polypoid lesion is connected to the wall base via a stalk (pedicle), consistent with pedunculated adenoma.
Sessile polyp — sits on the wall with a broad base (>2/3 of polyp height) without stalk formation. May be flat or slightly elevated.
Report Sentence
A broad-based sessile polypoid lesion is seen in the ___ segment, consistent with sessile adenoma.
Presence of multiple polypoid lesions. 3-10 polyps suggest sporadic multiple polyps, >10 polyps suggest polyposis syndrome (FAP, AFAP, MAP). >100 polyps is diagnostic for classic FAP.
Report Sentence
A total of ___ polypoid lesions are seen throughout the colon; clinical/genetic evaluation for polyposis syndrome is recommended.
Criteria
Most common type (80%). Forms tubular glandular structures. Villous component <25%.
Distinct Features
Usually small (<10 mm), pedunculated morphology common. Lowest malignant transformation risk (5%).
Criteria
Villous component 25-75%. Accounts for 15% of cases.
Distinct Features
Medium size (10-20 mm), sessile morphology more common. Intermediate malignant transformation risk (20%).
Criteria
Villous component >75%. Accounts for 5% of cases. Highest malignancy risk.
Distinct Features
Usually large (>20 mm), sessile or carpet-type lesion. Common in rectum. May secrete mucin. Malignant transformation risk 40-50%. May appear as large, lobulated, low-density (mucinous) mass on CT.
Distinguishing Feature
Adenocarcinoma shows transmural invasion, pericolic fat stranding, lymphadenopathy, and distant metastasis. Adenomatous polyp is mucosal-limited, wall is intact, no fat stranding.
Distinguishing Feature
Lipoma appears as homogeneous mass of fat density (-50 to -100 HU) without enhancement. Adenomatous polyp is soft tissue density (30-60 HU) with enhancement.
Distinguishing Feature
FAP has >100 polyps with diffuse distribution throughout the colon. Sporadic adenomatous polyp is usually <3 and focal. Confirmed by genetic testing.
Distinguishing Feature
Villous adenoma is usually >20 mm, sessile/carpet-type, and may secrete mucin. Standard adenomatous polyp is smaller, may be pedunculated, and does not secrete mucin. Histologic differentiation required.
Urgency
routineManagement
surgicalBiopsy
NeededFollow-up
3-monthTreatment of adenomatous polyps is colonoscopic polypectomy. Pedunculated polyps are removed by snare polypectomy, sessile polyps by EMR or ESD. Histopathologic examination determines dysplasia grade and presence of malignant focus. Surgical resection may be needed for incompletely removed or malignancy-containing polyps. Follow-up colonoscopy is planned by risk group: low-risk (1-2 tubular adenoma <10 mm) → 5-10 years, high-risk (≥3 adenomas, >10 mm, villous, HGD) → 3 years. If polyposis syndrome is detected, genetic counseling and family screening are initiated.
Premalignant lesion for colorectal cancer. Size (>10mm), villous histology, and high-grade dysplasia increase risk of malignant transformation. Removed by colonoscopic polypectomy.