Appendiceal lipoma is a rare, benign tumor composed of mature adipose tissue in the appendiceal wall (usually submucosa). Gastrointestinal lipomas are most common in the colon; appendiceal location is quite rare. Generally asymptomatic and an incidental CT or colonoscopy finding. However, large lipomas can serve as lead points for appendiceal intussusception or cause luminal obstruction. On CT, it appears as a well-defined, homogeneous mass at fat density (-70 to -130 HU) — these density values are diagnostic.
Age Range
35-70
Peak Age
50
Gender
Equal
Prevalence
Appendiceal lipoma arises from benign proliferation of mature adipocytes in the appendiceal submucosa. Whether this tumor is a true neoplasm or hamartomatous growth is debated; however, cytogenetic studies have demonstrated 12q13-15 chromosomal rearrangement, supporting neoplastic nature. As the lipoma grows, it protrudes into the appendiceal lumen and can create intraluminal obstruction. Large lipomas extend into the lumen as polypoid masses and can become intussusception lead points by being pulled by peristaltic movements. On imaging, the specific physical properties of adipose tissue — low X-ray attenuation (CT: -70 to -130 HU), high T1 signal (short T1 relaxation), signal loss on fat suppression — allow lipoma diagnosis with high reliability. Absence of septation, enhancement, or calcification within fat tissue supports benign character; when these features are present, liposarcoma should be considered, though liposarcoma in the appendix is extremely rare.
Homogeneous, well-defined, fat-density (-70 to -130 HU) mass in the appendiceal wall. This density value is pathognomonic for fat tissue and establishes lipoma diagnosis with high reliability. Absence of enhancement and homogeneous internal structure support benign nature.
Well-defined, homogeneous, fat-density (-70 to -130 HU) mass in the appendiceal wall (usually submucosal). Mass may protrude toward the appendiceal lumen. No internal septation, nodular component, or calcification.
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A well-defined, homogeneous fat-density (__ HU) mass measuring __ x __ mm in the appendiceal wall is observed, compatible with lipoma.
High signal intensity mass in the appendiceal wall on T1-weighted sequences — isointense to subcutaneous fat. Signal markedly drops on fat-suppressed T1 (fat-sat or Dixon) — confirming fat content. Homogeneous signal distribution supports benign nature.
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A high signal intensity mass in the appendiceal wall is observed on T1-weighted sequences, with signal loss on fat suppression supporting lipoma diagnosis.
Lipoma shows intermediate-to-high signal intensity on T2-weighted sequences. Signal markedly drops on fat-suppressed T2 (STIR). Homogeneous internal structure and smooth margins support benign nature.
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The mass shows intermediate-to-high signal on T2-weighted sequences, with signal loss on STIR confirming fat content.
Hyperechoic, well-defined, oval mass in the appendiceal wall on ultrasonography. Shows soft deformation with compression (soft nature of fat tissue). Posterior acoustic enhancement or mild attenuation may be seen. No vascularity on Doppler.
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A hyperechoic, well-defined, compressible mass in the appendiceal wall is observed, compatible with lipoma.
Lipoma shows no enhancement on contrast-enhanced CT — pre and post contrast density values are similar. This finding confirms that the lipoma consists of avascular mature adipose tissue and is critical in differentiating from enhancing solid tumors.
Report Sentence
No enhancement is observed in the mass on contrast phase, consistent with lipoma diagnosis.
Criteria
Localized fat mass in the appendiceal submucosa. Most common location. Protrudes into the lumen as a smooth, polypoid mass over the mucosa.
Distinct Features
Pillow sign on colonoscopy — soft deformation and recoil when pressed with biopsy forceps. Submucosal location clearly visible on CT.
Criteria
Localized fat mass beneath the appendiceal serosa. Rarer. Shows exophytic growth.
Distinct Features
Fat-density mass protruding outward from the outer contour of the appendix on CT. Minimal luminal effect. Lower likelihood of being an intussusception lead point.
Distinguishing Feature
LAMN shows cystic dilatation and low but positive density (0-20 HU) mucinous content. Lipoma shows negative density (-70 to -130 HU) fat content — density measurement provides definitive differentiation.
Distinguishing Feature
Neuroma is a small soft tissue density (30-50 HU) nodule without fat density. Lipoma shows negative density (-70 to -130 HU).
Distinguishing Feature
Intussusception shows invaginated appendix with target sign within the cecum. Lipoma appears as an isolated fat-density mass; however, large lipomas can be lead points for intussusception.
Distinguishing Feature
Appendicolith is a high-density (>100 HU) calcified structure. Lipoma shows negative density (-70 to -130 HU) — completely opposite density values allow easy differentiation.
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
no-follow-upAppendiceal lipoma is a benign tumor that does not require treatment in most patients. Homogeneous, well-defined, non-enhancing mass at fat density on CT is diagnostic and biopsy is not needed. No follow-up indication for asymptomatic small lipomas. Surgical resection (laparoscopic appendectomy) is curative for symptomatic lipomas (obstructive symptoms, intussusception, recurrent right lower quadrant pain). If heterogeneous internal structure, enhancing solid component, or size >5 cm, surgical excision or biopsy should be considered to exclude liposarcoma — however, liposarcoma at appendiceal location has been reported at the case report level in literature.
Appendiceal lipoma is a benign lesion with no risk of malignant transformation. No treatment is required in asymptomatic cases. Surgical excision is curative in symptomatic cases (obstruction, intussusception). It can be confidently diagnosed by homogeneous fat density/signal on CT or MRI and does not require biopsy.