by Bibianna Purgina, MD FRCPC
August 25, 2023
A lipoma is a non-cancerous tumour made up of fat cells. Most lipomas occur in the skin but this tumour can be found almost anywhere in the body.
A lipoma cannot turn into cancer over time. However, tumours that are incompletely removed can grow back.
Most lipomas are called idiopathic which means we do not know what causes them. The genetic syndromes familial lipomatosis and PTEN hamartoma syndrome are associated with the development of multiple lipomas.
Most lipomas in the skin are slow-growing and not associated with any symptoms. Lipomas on the neck or back may cause pain due to pressure on the tumour when lying down. Lipomas in other parts of the body also usually do not cause any symptoms and are discovered incidentally (by accident) when imaging is performed for another reason.
The diagnosis can be made after part or all of the tumour is surgically removed and sent to a pathologist for examination under a microscope. Under the microscope, lipomas look nearly identical to normal fat.
MDM2 is a gene that promotes cell division (the creation of new cells). Normal cells and those in lipomas have two copies of the MDM2 gene. In contrast, some cancers that look like a lipoma have more than two copies of the MDM2 gene.
Fluorescence in situ hybridization (FISH) is a test that allows pathologists to count the number of gene copies in a cell. A normal copy number or a normal ratio of MDM2 to a control gene such as CEP12 confirms that the tumour is a non-cancerous lipoma.