A lipomatous lesion is a medical term for a lump or growth composed of fat cells. While discovering a lump can be unsettling, these lesions are frequently non-cancerous. This article provides information about lipomatous lesions, helping you understand their nature and what steps might be involved.
Understanding Lipomatous Lesions
A lipomatous lesion is a growth made up of mature fat cells (adipocytes). These growths present as soft, doughy, or rubbery masses that move easily with slight finger pressure, often giving a “slippage sign.” They are usually painless, though some can cause discomfort if they contain many blood vessels or press on nearby nerves.
These lesions grow slowly and vary in size; most are less than 2 inches (5 centimeters) in diameter. While they commonly appear just beneath the skin, particularly on the neck, shoulders, back, abdomen, arms, and thighs, they can also occur deeper within tissues, including muscles or organs. Lipomatous lesions are among the most common soft tissue tumors found in adults, with an estimated prevalence of about 1% to 2% of the general population.
Differentiating Types of Lipomatous Lesions
The term “lipomatous lesion” is broad, encompassing various types of fatty growths that range from harmless to, in rare instances, cancerous. Understanding these distinctions is important for evaluation and management.
Benign Lipoma
The most common type is a benign lipoma, a non-cancerous tumor made purely of fat tissue. These are harmless, slow-growing, and do not spread to other parts of the body. They remain stable in size after reaching their final growth. About 5% to 10% of individuals may develop multiple lipomas, a condition known as lipomatosis, which can be linked to genetic factors.
Atypical Lipomatous Tumor (ALT)
Atypical Lipomatous Tumor (ALT) is a borderline lesion, not outright cancerous but warranting closer monitoring. ALTs are locally aggressive and can grow larger over time, reaching significant sizes. While ALTs in the limbs do not spread to distant sites, they have a low potential to transform into a more aggressive, malignant form, known as dedifferentiated liposarcoma. These tumors show atypical cells and genetic changes.
Liposarcoma
Liposarcoma represents the malignant, or cancerous, form of a fatty tumor. Unlike benign lipomas, liposarcomas grow deeper within the body, in the arms, legs, or abdomen, and may feel firmer. While rare compared to benign lipomas, liposarcomas can grow rapidly and may cause symptoms such as pain, swelling, or numbness if they compress nearby nerves or organs. A biopsy is needed to distinguish liposarcoma from other fatty lesions, as imaging alone may not always provide a definitive diagnosis due to their similar appearance to some benign lipomas.
Identifying Lipomatous Lesions
The process of identifying a lipomatous lesion begins with a physical examination, followed by imaging studies and, in some cases, a tissue biopsy for a definitive diagnosis.
Many people first notice a lipomatous lesion as a soft lump under the skin. A healthcare provider will then perform a physical examination, feeling the lump to assess its size, consistency, mobility, and any associated pain.
If there is any uncertainty or if the lesion is large or deep-seated, imaging techniques are employed. Ultrasound is the initial imaging method for superficial lesions, as it can show the fatty nature of the mass and its relationship to surrounding structures. For a more detailed assessment, particularly for larger or deeper lesions, Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans are used. MRI is preferred as it provides excellent soft tissue contrast and can help differentiate between fatty and non-fatty components, though distinguishing a benign lipoma from a low-grade liposarcoma can still be challenging with imaging alone.
When malignancy is suspected, or to definitively differentiate between types of lipomatous lesions, a biopsy is performed. This procedure involves removing a small tissue sample from the lump, which is then examined under a microscope by a pathologist. A biopsy is considered the gold standard for diagnosis and is important for lesions that are growing rapidly, are painful, or have an unusual appearance.
Managing Lipomatous Lesions
Once a lipomatous lesion is diagnosed, the management approach depends on its type, size, location, and whether it is causing symptoms.
Many benign lipomas do not require treatment and can be monitored over time if they are small, painless, and not growing. This observational approach is common for asymptomatic lesions, as they pose no health risk.
Surgical removal, or excision, is the most common and effective treatment for lipomas. This procedure is recommended for cosmetic reasons, if the lipoma is causing pain or discomfort by pressing on nerves, if it is growing rapidly, or if there is any suspicion of malignancy. The surgery is an outpatient procedure performed under local anesthesia, aiming to completely remove the fatty lump and its surrounding capsule to minimize recurrence. Other less common methods for smaller lesions include liposuction, which uses a needle and syringe to extract the fatty tissue, or steroid injections that can shrink the lesion, though these may not result in complete removal and recurrence is possible.
After diagnosis or treatment, follow-up care is advised for larger or atypical lesions, to monitor for any changes or recurrence. You should seek medical advice if you notice a new lump, if an existing lump rapidly grows, becomes painful, changes in consistency (e.g., becomes hard or fixed), or if it is accompanied by other concerning symptoms like fever or unexplained weight loss.