Colorectal lipoma is a benign tumor composed of mature adipose tissue originating from the submucosal layer of the colon and rectum. It is the second most common cause of gastrointestinal submucosal tumors, accounting for approximately 4% of colonic lesions. Most commonly found in the cecum, ascending colon, and sigmoid colon. Usually asymptomatic and incidentally detected; however, large lipomas (>4 cm) can cause intussusception, obstruction, or bleeding. Homogeneous fat density (-50 to -100 HU) on CT is a pathognomonic diagnostic finding and usually requires no further imaging. No risk of malignant transformation; endoscopic or surgical excision is curative for symptomatic lesions.
Age Range
40-70
Peak Age
55
Gender
Female predominant
Prevalence
Uncommon
Colorectal lipoma arises from benign proliferation of adipocytes (fat cells) in the submucosal layer. Mature adipose tissue is organized in lobular pattern and surrounded by thin fibrous septa; this organization is histologically identical to lipomas elsewhere in the body. The tumor does not invade surrounding tissue but protrudes toward the lumen compressing the mucosa as it grows (polypoid appearance). Large lipomas (>4 cm) can be dragged within the lumen by peristaltic waves and serve as lead points for intussusception; this can lead to venous congestion and ischemia. The pathognomonic fat density (-50 to -100 HU) on CT results from the high triglyceride content and low atomic number/electron density of adipose tissue causing X-ray attenuation significantly lower than surrounding soft tissue. On MRI, fat signal appears bright on T1 (short T1 relaxation due to methylene protons) and shows signal loss on fat-suppression sequences.
Homogeneous fat density between -50 and -100 HU in submucosal location on non-contrast CT — pathognomonic for lipoma and not seen in any other colorectal lesion (except liposarcoma, which is heterogeneous).
Well-defined, oval or round, homogeneous fat-density (-50 to -100 HU) submucosal mass in the colon on non-contrast CT. Internal structure is homogeneous; contains no soft tissue component, calcification, or enhancement. The mucosal layer over the mass is intact and smooth. Submucosal location is recognized by the lesion's position between the bowel wall and lumen.
Report Sentence
A well-defined mass measuring approximately ... mm with homogeneous fat density (-... HU) is seen in the submucosal location of the colon; consistent with colorectal lipoma.
Well-defined mass showing markedly hyperintense signal on T1-weighted images. Signal intensity is equivalent to subcutaneous fat. T1 bright signal results from short T1 relaxation time (efficient spin-lattice relaxation of triglyceride methylene protons). Mass is homogeneous and contains no soft tissue component except internal septa.
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The mass shows hyperintense signal equivalent to subcutaneous fat on MRI T1-weighted images, consistent with macroscopic fat content.
Complete signal loss of the mass on fat-suppressed sequences (STIR or frequency-selective fat sat); this finding confirms macroscopic fat content. Signal loss should be homogeneous and complete; focal signal retention (area not suppressed) suggests soft tissue component and raises liposarcoma in differential.
Report Sentence
Complete signal loss of the mass on fat-suppressed sequences confirms macroscopic fat content; fully consistent with benign lipoma.
Appears as a well-defined, homogeneous hyperechoic mass in the submucosal location on ultrasound. Echogenicity is similar to subcutaneous fat. Posterior acoustic enhancement may be observed. Mucosal layer is intact and stretches smoothly over the mass. No vascularity on Doppler examination.
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A well-defined, homogeneously hyperechoic, avascular mass is seen in the submucosal location of the colon on ultrasound, consistent with lipoma.
Lipoma shows no enhancement on contrast-enhanced CT; density remains identical to non-contrast scan values. This finding confirms the avascular structure and benign character of the lesion. Thin septa may show slight enhancement but the main mass density does not change. Presence of enhancing soft tissue component suggests liposarcoma diagnosis.
Report Sentence
Absence of enhancement is confirmed on contrast-enhanced series; avascular fat-density lesion supports the diagnosis of benign lipoma.
Large lipomas (>4 cm) may present as intussusception lead points. In this case, a fat-density mass (lead point) is detected within the target sign. The fat density of lipoma makes the lead point identifiable as benign lipoma even in the context of intussusception. Proximal bowel dilatation and air-fluid levels may accompany.
Report Sentence
A fat-density lead point is identified within the intussusception mass, suggesting lipoma-related intussusception.
Criteria
Submucosal origin, covered by intact mucosa, intraluminal polypoid or sessile mass. Most common type; predominant in cecum and ascending colon.
Distinct Features
Homogeneous fat density, no enhancement, endoscopic cushion sign positive.
Criteria
Lipoma larger than 4 cm; carries risk of intussusception, obstruction, or bleeding. Symptomatic group with surgical indication.
Distinct Features
Same fat density but large size, obstruction findings may accompany, may be intussusception lead point.
Criteria
Rare lipoma variant located outside submucosa, in subserosa or muscularis propria. May show exophytic growth. Appears as pericolic fat-density mass on CT.
Distinct Features
Exophytic growth pattern, pericolic location, same fat density. Homogeneity important in liposarcoma differential.
Distinguishing Feature
Leiomyoma is at soft tissue density (30-50 HU) without fat; lipoma is at pathognomonic fat density (-50 to -100 HU).
Distinguishing Feature
GIST is a heterogeneously enhancing soft tissue density mass without fat; lipoma is homogeneous fat density and avascular.
Distinguishing Feature
Adenomatous polyp is enhancing intraluminal lesion at soft tissue density; lipoma is non-enhancing submucosal mass at fat density.
Distinguishing Feature
Liposarcoma is heterogeneous with soft tissue component, thick septa, and enhancement alongside fat density; lipoma is distinguished by homogeneous fat signal and absence of enhancement.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upColorectal lipoma is a benign tumor with no risk of malignant transformation. Small (<4 cm), asymptomatic lipomas require no follow-up; no additional workup needed after CT fat density diagnosis. Symptomatic or large (>4 cm) lipomas are treated with endoscopic polypectomy or surgical excision. Surgical resection is required for cases with intussusception. Recurrence rate is extremely low.
Benign lesion that does not require treatment. Large lipomas (>4 cm) may cause intussusception or obstruction. Definitive diagnosis is made by fat density; biopsy is not needed.