Lipoma: Symptoms, Types, Causes and Treatment

Lipomas are among the most common benign tumors found in humans. Although generally harmless and slow-growing, their presence can sometimes lead to discomfort, functional issues, or cosmetic concerns. Understanding their symptoms, diverse types, underlying causes, and the full spectrum of treatment options is essential for both patients and healthcare providers. This article brings together current research to offer a detailed, evidence-based overview of lipomas.

Symptoms of Lipoma

Lipomas are often discovered incidentally, as they may remain asymptomatic for years. However, when symptoms do occur, they can vary depending on the lipoma's size, location, and involvement with surrounding tissues. Recognizing these symptoms can help with timely diagnosis and management.

Symptom	Description	Frequency/Pattern	Source(s)
Lump	Soft, mobile, painless mass	Most common	2 6 7
Pain	Discomfort or tenderness	May occur if pressing on nerves or vessels	1 2 6
GI symptoms	Abdominal pain, nausea, bleeding	With gastrointestinal lipomas	1 8
Mechanical	Restriction of movement, joint pain	With intra-articular or musculoskeletal lipomas	2 11

Table 1: Key Symptoms

Common Presentations

The classic symptom of a lipoma is a soft, doughy, and mobile lump under the skin. Most lipomas are not painful and can range from less than a centimeter to several centimeters in diameter. However, they may cause discomfort if they press on nearby nerves or tissues, especially in confined spaces such as the hand, foot, or spinal canal 2 6.

Location-Specific Symptoms

• Gastrointestinal Lipomas: These can manifest with abdominal pain, nausea, vomiting, gastrointestinal bleeding, constipation, and weight loss, especially when larger or in critical locations like the small bowel or colon 1 8.
• Musculoskeletal and Intra-articular Lipomas: Lipomas within muscles or joints may cause mechanical symptoms such as restricted movement or joint swelling, sometimes leading to misdiagnosis as other joint diseases 2 6 11.
• Cardiac Lipomas: Rarely, lipomas within the heart can cause chest pain, palpitations, or even syncope, depending on their size and location 10.

When Symptoms Warrant Concern

While most lipomas are harmless, rapid growth, persistent pain, or changes in characteristics (such as hardness or fixation to surrounding tissues) should prompt further medical evaluation to rule out malignancies such as liposarcoma 4.

Types of Lipoma

Lipomas are not a uniform entity; they comprise a spectrum of subtypes, distinguished by location, cellular composition, and clinical behavior. Knowledge of these varieties is vital for accurate diagnosis and management.

Type	Distinguishing Feature	Common Location(s)	Source(s)
Conventional	Mature fat cells	Subcutaneous tissue	2
Spindle cell	Spindle-shaped cells	Posterior neck, shoulders	2 3
Intramuscular	Within muscle tissue	Trunk, limbs	6
Intermuscular	Between muscle groups	Anterior abdominal wall	6
Intraosseous	Inside bone	Long bones (e.g., femur)	2 5
Angiolipoma	Vascular component	Forearm, trunk	2
Lipoma arborescens	Villous projections in synovium	Knee joint	2 11
Cardiac	Within heart/pericardium	Cardiac chambers, pericardium	10
GI lipoma	GI tract submucosa	Colon, small bowel	1 8
Posttraumatic	Linked to trauma	Variable	7

Table 2: Lipoma Types

Conventional and Subcutaneous Lipomas

These are the most common type, presenting as soft, mobile masses in the subcutaneous tissues. They usually grow slowly and are benign 2.

Spindle Cell and Pleomorphic Lipomas

Spindle cell lipomas predominantly occur in middle-aged men and are mainly found on the posterior neck and shoulders. They can resemble malignant tumors but have an excellent prognosis with local excision 3.

Intramuscular and Intermuscular Lipomas

• Intramuscular Lipomas: These are found within muscle tissue and may be infiltrative or well-circumscribed. The infiltrative type has a notable risk for recurrence after excision 6.
• Intermuscular Lipomas: Located between muscles, these are rarer and less likely to recur 6.

Intraosseous Lipomas

Occurring within bones, intraosseous lipomas can cause pain or be discovered incidentally on imaging. They may undergo stages of fat cell death and calcification, sometimes mimicking other bone lesions 5.

Angiolipoma, Myolipoma, and Others

• Angiolipomas contain a prominent vascular component and often present as tender subcutaneous nodules, especially in the forearm 2.
• Myolipomas, chondroid lipomas, and hibernomas are rarer subtypes with unique histological features 2.

Lipoma Arborescens

A rare intra-articular variant, lipoma arborescens, primarily affects the knee and is characterized by villous fatty proliferation of the synovium, leading to joint swelling and pain 2 11.

Cardiac and Gastrointestinal Lipomas

• Cardiac Lipomas can occur anywhere in the heart and may present with a variety of cardiac symptoms or be found incidentally 10.
• Gastrointestinal Lipomas are slow-growing submucosal tumors that may cause bleeding or obstruction if large 1 8.

Posttraumatic Lipomas

These are thought to develop at sites of blunt trauma, possibly due to fat tissue herniation or inflammatory changes triggering fat cell proliferation 7.

Causes of Lipoma

The precise reasons why some people develop lipomas remain an area of ongoing research. However, several contributing factors and hypotheses have been identified.

Cause	Mechanism/Description	Evidence/Notes	Source(s)
Genetic	Familial predisposition, certain syndromes	Familial multiple lipomatosis, inherited cases	2
Trauma	Fat necrosis or herniation after injury	Posttraumatic formation, “pseudolipoma”	7
Cellular	Differentiation of preadipocytes	Triggered by local factors (e.g., trauma)	7
Idiopathic	Unknown/unidentified causes	Most cases have no clear cause	2 7

Table 3: Causes of Lipoma

Genetic Factors

• Lipomas may run in families, and certain rare conditions, such as familial multiple lipomatosis, are characterized by the presence of multiple lipomas across generations 2.
• Some genetic syndromes are linked to multiple or atypical lipomas.

Trauma and Local Factors

• Blunt trauma is implicated in the development of some lipomas, possibly by creating a local environment that promotes the transformation of preadipocytes (immature fat cells) into mature fat cells, or by causing herniation of deeper fat into subcutaneous tissue 7.
• Not all trauma leads to lipoma; it may require fat necrosis and subsequent inflammatory response to trigger lipoma formation 7.

Cellular and Molecular Pathways

• The precise cellular mechanisms remain unclear, but local growth factors, inflammation, and preadipocyte differentiation all likely play a role, especially in posttraumatic and infiltrative types 7.

Idiopathic Nature

• For most individuals with a single lipoma, no identifiable cause is found, and these are considered idiopathic 2.

Treatment of Lipoma

Treatment is tailored to the individual, considering factors such as symptoms, lipoma size, location, and patient preference. Most lipomas are benign and do not require removal unless they cause discomfort or functional or cosmetic concerns.

Treatment	Method/Description	Indication/Outcome	Source(s)
Excision	Surgical removal	Symptomatic, large, uncertain diagnosis	2 3 6 10
Endoscopic	Removal via endoscopy (GI lipomas)	GI lipomas, less invasive	1 8
Arthroscopic	Synovectomy for intra-articular	Lipoma arborescens	11
Non-surgical	Observation, monitoring	Asymptomatic, small lipomas	2 5
Injection	Deoxycholate injection	Small, superficial lipomas	9

Table 4: Lipoma Treatment Options

Surgical Excision

• Standard Treatment: Simple surgical excision is the gold standard for most lipomas, especially when symptomatic, large, or rapidly growing. The procedure is typically curative with low recurrence rates, except for infiltrative intramuscular types 2 3 6.
• Musculoskeletal and Cardiac Lipomas: Surgery is also effective for intraosseous, intramuscular, and cardiac lipomas, though the approach may vary depending on anatomical complexities 5 6 10.
• Complicated Locations: In high-risk areas, such as the heart, complete excision may sometimes be challenging if the lipoma infiltrates surrounding tissues 10.

Minimally Invasive and Endoscopic Techniques

• Gastrointestinal Lipomas: Endoscopic removal is increasingly used for GI lipomas, especially those causing symptoms or complications. Techniques include endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD), with high rates of success and low risk of complications 1 8.
• Arthroscopic Synovectomy: For lipoma arborescens (especially in the knee), arthroscopic treatment is highly effective, with a success rate above 95% and minimal recurrence 11.

Non-Surgical and Observation

• Watchful Waiting: Asymptomatic and small lipomas often do not require treatment, and observation is a valid approach, especially when the diagnosis is clear and there is no suspicion of malignancy 2 5.
• Intraosseous Lipomas: Many intraosseous lipomas undergo spontaneous involution and may not need surgery unless symptomatic 5.

Injectable Treatments

• Deoxycholate Injections: For those seeking non-surgical options, especially for smaller superficial lipomas, injections of deoxycholate have shown promise in reducing lipoma size with minimal side effects. However, more research is needed to confirm long-term safety and efficacy 9.

Other Considerations

• Recurrence: Most lipomas do not recur after complete excision, though infiltrative types (particularly intramuscular lipomas) carry a higher risk 6.
• Malignancy: If there is uncertainty regarding the diagnosis, or if the lipoma demonstrates atypical features (rapid growth, pain, fixation), excision and histopathological examination are essential to rule out liposarcoma 4.

Conclusion

Lipomas are a diverse group of benign fatty tumors that can arise in virtually any part of the body. While most are harmless, understanding their symptoms, types, causes, and available treatments is essential for informed decision-making and optimal care.

Key takeaways:

• Symptoms: Most lipomas are painless, soft, and mobile, but location-specific symptoms can occur, especially in the gastrointestinal tract, joints, or muscles.
• Types: There is a broad spectrum of lipoma types, including subcutaneous, intramuscular, intraosseous, and specialized forms such as spindle cell, angiolipoma, and lipoma arborescens.
• Causes: While many lipomas are idiopathic, genetics and trauma can play a role in certain cases.
• Treatment: Options range from observation and minimally invasive techniques to surgical excision, with excellent outcomes in most cases. Novel therapies like deoxycholate injections are emerging for select patients.

If you notice a new or rapidly growing lump, or experience unusual symptoms associated with an existing lipoma, consult a healthcare professional for evaluation and guidance on the most appropriate management strategy.