From the Guidelines
Lipomas are typically mobile, as they can often be moved around beneath the skin with gentle pressure from the fingers, and this mobility is an important clinical characteristic that helps distinguish lipomas from other types of growths. These benign fatty tumors are composed of mature fat cells that grow slowly in the subcutaneous tissue, between the skin and underlying muscle layer. When examined by touch, lipomas can usually be moved around beneath the skin with gentle pressure from the fingers. This mobility is due to the fact that lipomas are encapsulated in a thin fibrous tissue that separates them from surrounding structures, allowing them to slide within the subcutaneous space 1.
Some key characteristics of lipomas include:
- They are usually solitary lesions, but multiple lipomas can occur
- They can have a yellow hue on endoscopy
- They often exhibit a pillow sign when probed with closed biopsy forceps
- They may exhibit some mobility, which is an important diagnostic feature 1
- On endoscopic ultrasonography (EUS) examination, they appear as intensely hyperechoic well-circumscribed masses arising from the submucosal wall layer, which is essentially diagnostic for a lipoma 1.
However, some lipomas may feel less mobile if they are located in areas with tighter tissue planes or if they grow between muscle fibers (intramuscular lipomas) 1. Additionally, very large lipomas or those that have been present for many years might develop attachments to surrounding tissues, potentially reducing their mobility. This characteristic mobility is one feature doctors use during physical examination to help diagnose a lipoma before considering further testing.
From the Research
Lipoma Mobility
- Lipomas are typically described as mobile or non-mobile based on their location and encapsulation.
- Subcutaneous lipomas, which are the most common type, are usually mobile due to their location under the skin and lack of deep tissue involvement 2.
- Deep-seated lipomas, on the other hand, may be less mobile due to their location under the enclosing fascia or within the muscle 2.
- Non-encapsulated lipomas may also be less mobile due to their infiltration into surrounding tissues 3.
Factors Affecting Lipoma Mobility
- Encapsulation: Encapsulated lipomas tend to be more mobile than non-encapsulated ones 3.
- Location: Subcutaneous lipomas are generally more mobile than deep-seated lipomas 2.
- Size: Larger lipomas may be less mobile due to their size and potential infiltration into surrounding tissues 4.
- Tissue involvement: Lipomas that infiltrate into surrounding tissues, such as muscle or fascia, may be less mobile than those that do not 2, 5.
Imaging Characteristics
- MRI features of lipomas can help distinguish them from other fatty tumors and assess their mobility 5, 4.
- Ultrasound and optoacoustic imaging can also be used to visualize lipomas and assess their mobility 6.
- Imaging characteristics, such as fat suppression and contrast enhancement, can provide information about the lipoma's composition and potential mobility 4.