Ultrasound Features of Lipomas

Key Sonographic Characteristics

Lipomas most commonly arise from the submucosal layer (third layer) on endoscopic ultrasound, according to the American Gastroenterological Association 1, 2, 3
Lipomas appear intensely hyperechoic compared to surrounding tissues, as reported by the American College of Gastroenterology 2
Some lipomas may contain thin, curved echogenic lines within the mass, with minimal to no internal vascularity on Doppler examination, as noted by the American College of Radiology 4
No acoustic shadowing is typically observed in lipomas, according to the American College of Radiology 4

When combined with endoscopic evaluation, the "pillow sign" (indentation when pressed with biopsy forceps) is highly suggestive of a lipoma with 98% specificity, as reported by the American Gastroenterological Association 1

Endoscopic ultrasound (EUS) is the modality of choice for evaluating subepithelial lesions including lipomas, as recommended by the American College of Gastroenterology 2, 3
For superficial lipomas, conventional ultrasound provides accurate identification with high sensitivity (94.1%) and specificity (99.7%), according to the American College of Radiology 4
When ultrasound features are typical (hyperechoic, well-circumscribed, minimal vascularity), further imaging may not be necessary, as suggested by the American College of Radiology 4
Atypical features warrant additional evaluation, which may include contrast-enhanced imaging or tissue sampling, as recommended by the American College of Radiology 4

A benign tumor composed of mature adipocytes encapsulated in fibrous tissue is definitively a lipoma, not a fibroma 5, 6, 7
Histologically, lipomas consist of mature adipocytes that are relatively uniform in size and lack cytologic atypia 5

On endoscopic ultrasound (EUS), lipomas appear as intensely hyperechoic, well-circumscribed masses arising from the submucosal wall layer (3rd layer) 5, 6, 7
On endoscopy, lipomas often have a yellow hue and exhibit a "pillow sign" when probed with closed biopsy forceps 6, 7
The pillow sign has high specificity (98%) but lower sensitivity (40%) for identifying lipomas 6, 7

Lipomas are typically benign, slow-growing lesions but can cause clinical symptoms in some cases 6, 7
Symptoms may include bleeding (if ulceration occurs), obstruction, or pain depending on location and size 6, 7
For asymptomatic, small lipomas with classic imaging features, observation may be appropriate 8
For symptomatic lipomas or those with uncertain diagnosis, complete surgical excision is the standard treatment 8

Radiographs are the traditional first step in evaluating soft tissue masses, but may be unrewarding for small, deep-seated, or non-mineralized masses, according to the American College of Radiology 9, 10
Radiographs can identify intrinsic fat in only about 11% of soft tissue masses, as reported by the American College of Radiology 9
Ultrasound has emerged as the most useful initial imaging modality for suspected lipomas, especially for superficial lesions, as recommended by the American College of Radiology 9, 10

Physical examination alone is insufficient, as it correctly identifies only about 85% of lipomas, highlighting the importance of diagnostic testing, according to the American College of Radiology 9