- Lipomas are the most common soft tissue tumors.
- Most are subcutaneous and composed of normal adipose tissue.
- Slow growing, often asymptomatic, and usually diagnosed by palpation
- Enveloped by a thin, fibrous capsule
- Reported to occur after trauma
- Lipomas rarely, if ever, become malignant but must be differentiated from liposarcomas and other tumors.
- They can occur at any age but are most common in middle-aged adults, peaking in the 40- to 60-year age group.
- They are rare <20 years of age.
Occur in about 1% of population
- Soft tissue trauma frequently has been cited as a cause, especially if the patient develops a posttraumatic hematoma.
- Alcohol consumption may be a predisposing factor for Madelung disease, or benign symmetric lipomatosis, with lipomas on the head, neck, shoulders, and proximal upper extremities. This may present with the characteristic “horse collar” cervical appearance.
- May appear as a hereditary trait in patients with hereditary multiple lipomatosis, an autosomal dominant condition. This is found most frequently in men, characterized by extensive symmetric lipomas mostly on extremities and trunk.
- Also seen in Gardner syndrome, a variant of familial adenomatous polyposis, an autosomal dominant disease characterized by gastrointestinal (GI) polyps, multiple osteomas, and skin and soft tissue tumors.
- Congenital lipomas have been observed in children.
- The pathogenetic link between soft tissue trauma and the formation of posttraumatic lipomas is still controversial.
- There are 2 potential explanations to correlate soft tissue trauma and adipose tissue tumor growth.
- The first is the formation of so-called posttraumatic pseudolipomas by prolapsing adipose tissue through fascia resulting from direct impact.
- A second possibility points toward lipoma formation as a result of preadipocyte differentiation and proliferation mediated by cytokine release following soft tissue trauma and hematoma formation.
They are reported to occur after trauma or after steroid injection, but most are idiopathic.
Commonly Associated Conditions
- Admixture of other tissue types leads to fibrolipomas, angiolipomas, and myolipomas.
- Unusual syndromes include the giant variety, hereditary multiple lipomatosis, adiposis dolorosa (multiple tender diffuse lesions), and Madelung disease (numerous, symmetrically distributed lipomas of the upper trunk).
- Liposarcomas rarely develop from benign lipomas. They can occur anywhere in the body, mostly in deep structures.
- Useful questions on history gathering are duration, associated symptoms, tenderness, recurrence, progression, similar lesions, and weight loss.
- Generally slow-growing; may take years before being noticed
- If fast growing, may indicate a liposarcoma
- Usually asymptomatic
- Infrequently may cause pain; seen with angiolipoma, a highly vascular lipoma
- If compression occurs, pressure or neuropathic symptoms may develop (mass effect) in locations such as the forearm or ankle.
- Most often patients show them to physicians for explanation and reassurance.
- They may be first noted by physicians on a physical exam.
- Lipomas are usually soft, homogeneous, oval, and nontender, and the overlying skin is mobile over them.
- They are commonly from 1–6 cm in diameter. If larger, this raises suspicion for liposarcoma.
- Rubbery or doughy consistency; if harder, suspect liposarcoma, sebaceous (epidermoid) cyst, or abscess
- Overlying skin is normal; if erythematous, might indicate an abscess.
- The tumor will be felt to slip out from under your fingers (“slippage sign”) as opposed to a sebaceous cyst or an abscess, which is tethered by surrounding induration.
- Individuals can have single lesions or a few. In ∼5% of cases, patients have multiple lesions.
- They are usually subcutaneous and often found in the upper trunk, especially the shoulders, back, neck, and head, but can be anywhere in or on the body.
- In the GI tract, lipomas present as submucosal fatty tumors. The most common locations include the esophagus, stomach, and small intestine. Symptoms occur from luminal obstruction or bleeding.
- Lipomas have been reported in anatomic locations as varied as cardiac, intrathoracic, endobronchial, retroperitoneal, breast, intermuscular, calf, thigh, scapular, intraosseous, fingers, palmar, toe, epidural, spinal, intraarticular (knee), parapharyngeal, nasopharyngeal, adrenal, inguinal, bladder, scrotal, ovarian, intracranial, intraneural, and GI tract (most often in the ileum).
Diagnostic Tests & Interpretation
Most subcutaneous lipomas can be diagnosed based on history and physical, and no imaging studies are required.
- Magnetic resonance imaging (MRI) and computed tomography scan are used mostly for atypical locations and as a preoperative measure.
- Because of differences in treatment, prognosis, and long-term follow-up, it is important to preoperatively distinguish simple lipomas from well-differentiated liposarcomas.
- MRI is highly sensitive in the detection of well-differentiated liposarcomas and highly specific in the diagnosis of simple lipomas.
- Reported MRI findings suggestive of liposarcoma include a partially ill-defined margin, neurovascular involvement, enhancing thick/nodular septum, and a partially bright signal intensity on T1 weighted images. A thick/nodular septum was identified as the most statistically significant predictor of liposarcoma (1).
- When an extremity or body wall lesion is considered suspicious for well-differentiated liposarcoma, it is more likely (64%) to represent one of many benign lipoma variants (2).
- If liposarcoma is suspected, fine- and core-needle aspirations have been proposed along with imaging.
- A core-needle biopsy has been proposed as the preferred biopsy method; it can provide accurate diagnosis and assessment of malignant potential and grade if examined by an experienced pathologist (3).
If diagnosis is uncertain, excisional biopsy is a preferred assessment tool.
- Lipomas are composed of adipose tissue, with varying amounts of a network of connective tissue.
- Lipomas differ from normal fat with increased levels of lipoprotein lipase and a larger number of precursor cells.
- In the subcutaneous location, the primary differential diagnosis is a sebaceous cyst or an abscess.
- Sebaceous (epidermoid) cysts are also rounded and subcutaneous. They can be differentiated from lipomas by their characteristic central punctum and surrounding induration.
- Benign lipomas must be differentiated from liposarcomas.
- Rapid growth and pain should prompt consideration of malignancy.
- Refer to History and Physical Exam for more clues on differential diagnosis.
- Most lipomas can be observed without treatment (4)[C].
- They need excision if there is diagnostic uncertainty, lack of homogeneity to palpation, rapid growth, associated pain, or cosmetic concern. Treatment is excision, but steroid injection or liposuction can be useful in certain locations (such as facial) (4)[C].
- A successful trial of lipomas treated with subcutaneous deoxycholate injections has been reported suggesting that low-concentration deoxycholate may be a relatively safe and effective treatment for small collections of fat. However, controlled clinical trials will be necessary to substantiate these observations (5).
- Spinal lipomas should be operated on as soon as possible on a prophylactic basis, and careful and constant follow-up should be carried out to permit prompt reintervention in cases with deterioration (6).
- Plan the incision to follow skin lines, if possible, to minimize scarring. Use a surgical marker to draw out the palpable margins of the lipoma and the planned incision. The incision should be about 60% of the lipoma width. Be prepared to extend the incision if needed.
- After anesthesia, a linear incision is carried out down to the level of the capsule using a number 11 or 15 blade.
- Blunt dissection (curved hemostat) and sharp dissection (iris scissor) are used to free up the lipoma and to separate it from the inferior normal tissue.
- As the lobule is lifted, the dissection is continued to free up the entire tumor.
- Apply pressure to the outside of the lipoma to express it through the skin opening (7). In many cases, the lipoma will just pop out. If not, more dissection may be needed, or the incision may be lengthened.
- After the lipoma is out, pressure with gauze is usually all that is needed to obtain good hemostasis. If bleeding persists, use electrocoagulation before closing the incision.
- The dead space may be closed with deep absorbable sutures, but often this is not necessary.
- The skin may be closed with nonabsorbable simple interrupted sutures. For small lipomas, closure may be performed with wound-closure strips or the linear incision left open.
- If excessive skin remains, the linear incision can be turned into an ellipse to avoid redundant skin.
Usual surgical follow-up is needed, with treatment of any hematoma formation or infection.
Handout: “What Are Lipomas?” American Family Physician, March 1, 2002; http://www.aafp.org/afp/20020301/905ph.html
Most lipomas grow very slowly and are benign, asymptomatic, and remain stable.
- Hematoma formation or infection is rare but possible.
- Occasionally a bilobar lipoma may be missed, resulting in “recurrence.”
- Lipomas that grow rapidly or become painful or nodular must be evaluated for liposarcoma.
1. Jaovisidha S, Suvikapakornkul Y, Woratanarat P, Subhadrabandhu T, Nartthanarung A, Siriwongpairat P et al. MR imaging of fat-containing tumours: the distinction between lipoma and liposarcoma.Singapore Med J. 2010;51:418–23.
2. Gaskin CM, Helms CA. Lipomas, lipoma variants, and well-differentiated liposarcomas (atypical lipomas): results of MRI evaluations of 126 consecutive fatty masses. AJR Am J Roentgenol. 2004;182:733–9.
3. Heslin MJ, Lewis JJ, Woodruff JM, et al. Core needle biopsy for diagnosis of extremity soft tissue sarcoma. Ann Surg Oncol. 1997;4:425–31.
4. Bancroft LW, Kransdorf MJ, Peterson JJ, et al. Benign fatty tumors: classification, clinical course, imaging appearance, and treatment. Skeletal Radiol. 2006;35:719–33.
5. Rotunda AM, Ablon G, Kolodney MS. Lipomas treated with subcutaneous deoxycholate injections. J Am Acad Dermatol. 2005;53:973–8.
6. La Marca F, Grant JA, Tomita T, et al. Spinal lipomas in children: outcome of 270 procedures. Pediatr Neurosurg. 1997;26:8–16.
7. Kenawi MM. ‘Squeeze delivery’ excision of subcutaneous lipoma related to anatomic site. Br J Surg. 1995;82:1649–50.
Aust MC, Spies M, Kall S, et al. Posttraumatic lipoma: fact or fiction? Skinmed. 2007;6:266–70.
Blount JP, Elton S. Spinal lipomas. Neurosurg Foc. 2001;10(1):e3.
Lellouch-Tubiana A, Zerah M, Catala M, et al. Congenital intraspinal lipomas: histological analysis of 234 cases and review of the literature. Pediatr Dev Pathol. 1999;2:346–52.
Salam GA. Lipoma excision. Am Fam Physician. 2002;65:901–4.
Springfield D. Liposarcoma. Clin Orthopaed Rel Res. 1993;(289):50–7.
- 214.0 Lipoma of skin and subcutaneous tissue of face
- 214.1 Lipoma of other skin and subcutaneous tissue
- 214.2 Lipoma of intrathoracic organs
- 214.3 Lipoma of intra-abdominal organs
- 214.4 Lipoma of spermatic cord
- 214.8 Lipoma of other specified sites
- 214.9 Lipoma, unspecified site
- 93163002 lipoma (disorder)
- 93159009 lipoma of skin and subcutaneous tissue of face (disorder)
- 188990009 lipoma of skin and subcutaneous tissue (excluding face) (disorder)
- 93158001 lipoma of intrathoracic organs (disorder)
- 93157006 lipoma of intra-abdominal organs (disorder)
- 93162007 lipoma of spermatic cord (disorder)
- Slow growing, often asymptomatic, and usually diagnosed by palpation
- Asymptomatic lipomas can be followed clinically and only need treatment if they cause pain, are growing rapidly, or become nonhomogeneous.
- Most symptomatic lipomas are removed surgically, but for small ones, liposuction or cortisone injection has been reported to be successful.
- In the subcutaneous location, the primary differential diagnosis is a sebaceous (epidermoid) cyst or an abscess.
- Consider subspecialty care if a lipoma in a delicate anatomic location needs removal or if there is concern that the lesion might be malignant.