|Classification and external resources|
Lipoma on forearm
|ICD-10||D17 (ILDS D17.910)|
A lipoma is a benign tumor composed of adipose tissue (body fat). It is the most common benign form of soft tissue tumor. Lipomas are soft to the touch, usually movable, and are generally painless. Many lipomas are small (under one centimeter diameter) but can enlarge to sizes greater than six centimeters. Lipomas are commonly found in adults from 40 to 60 years of age, but can also be found in younger adults and children. Some sources claim that malignant transformation can occur, while others say this has yet to be convincingly documented.
There are many subtypes of lipomas::624–5
- Adenolipomas are lipomas associated with eccrine sweat glands.:627
- Angiolipoleiomyomas are acquired, solitary, asymptomatic acral nodules, characterized histologically by well-circumscribed subcutaneous tumors composed of smooth muscle cells, blood vessels, connective tissue, and fat.:627
- Angiolipomas painful subcutaneous nodules having all other features of a typical lipoma.:624
- Cerebellar pontine angle and internal auditory canal lipomas
- Chondroid lipomas are deep-seated, firm, yellow tumors that characteristically occur on the legs of women.:625
- Corpus callosum lipoma is a rare congenital brain condition that may or may not present with symptoms. This occurs in the corpus callosum, also known as the colossal commissure, which is a wide, flat bundle of neural fibers beneath the cortex in the human brain.
- Hibernomas are lipoma of brown fat.
- Intradermal spindle cell lipomas are distinct in that they most commonly affect women and have a wide distribution, occurring with relatively equal frequency on the head and neck, trunk, and upper and lower extremities.:625
- Neural fibrolipomas are overgrowths of fibro-fatty tissue along a nerve trunk, which often leads to nerve compression.:625
- Pleomorphic lipomas, like spindle-cell lipomas, occur for the most part on the backs and necks of elderly men and are characterized by floret giant cells with overlapping nuclei.:625
- Spindle-cell lipomas are asymptomatic, slow-growing subcutaneous tumors that have a predilection for the posterior back, neck, and shoulders of older men.:625
- Superficial subcutaneous lipomas, the most common type of lipoma, lie just below the surface of the skin. Most occur on the trunk, thigh, and forearm, although they may be found anywhere in the body where fat is located.
Approximately one percent of the general population has a lipoma. These tumors can occur at any age, but are most common in middle age, often appearing in people from 40 to 60 years old. Cutaneous lipomas are rare in children, but these tumors can occur as part of the inherited disease Bannayan-Zonana syndrome.
Lipomas are usually relatively small with diameters of about 1–3 cm, but in rare cases they can grow over several years into "giant lipomas" that are 10–20 cm across and weigh up to 4–5 kg.
The tendency to develop a lipoma is not necessarily hereditary although hereditary conditions, such as familial multiple lipomatosis, may include lipoma development. Genetic studies in mice have shown a correlation between the HMG I-C gene (previously identified as a gene related to obesity) and lipoma development. These studies support prior epidemiologic data in humans showing a correlation between HMG I-C and mesenchymal tumors.
Cases have been reported where minor injuries are alleged to have triggered the growth of a lipoma, called "post-traumatic lipomas." However, the link between trauma and the development of lipomas is controversial.
Usually, treatment of a lipoma is not necessary, unless the tumor becomes painful or restricts movement. They are usually removed for cosmetic reasons, if they grow very large, or for histopathology to check that they are not a more dangerous type of tumor such as a liposarcoma. This last point can be important as the characteristics of a "bump" is not known until after it is removed and medically examined.
Lipomas are normally removed by simple excision. The removal can often be done under local anaesthetic, and takes less than 30 minutes. This cures the great majority of cases, with about 1–2% of lipomas recurring after excision. Liposuction is another option if the lipoma is soft and has a small connective tissue component. Liposuction typically results in less scarring; however, with large lipomas it may fail to remove the entire tumor, which can lead to regrowth.
Operating field after removal of the lipoma. Arrow marks the median nerve that was compressed by the lipoma.
Lipomas are rarely life-threatening and the common subcutaneous lipomas are not a serious condition. Lipomas growing in internal organs can be more dangerous, for example lipomas in the gastrointestinal tract can cause bleeding, ulceration and painful obstructions (so-called "malignant by location", despite being a benign growth histologically). Malignant transformation of lipomas into liposarcomas is very rare and most liposarcomas are not produced from pre-existing benign lesions. A few cases of malignant transformation have been described for bone and kidney lipomas, but it is possible these few reported cases were well-differentiated liposarcomas in which the subtle malignant characteristics were missed when the tumour was first examined. Deep lipomas have a greater tendency to recur than superficial lipomas, because complete surgical removal of deep lipomas is not always possible.
The presence of multiple lipomas is known as lipomatosis and is more commonly encountered in men. Some superficial lipomas can extend into deep fascia and may complicate excision. Liposarcoma is found in 1% of lipomas and are more likely in lesions of the lower extremities, shoulders and retroperitoneal areas. Other risk factors for liposarcoma include large size (>5 cm), associated with calcification, rapid growth and/or invasion into nearby structures or through fascia into muscle tissue.
In veterinary medicine
Lipomas occur in many animals, but are most common in older dogs, particularly older Labrador Retrievers, Doberman Pinschers and Miniature Schnauzers. Overweight female dogs are especially prone to developing these tumors and most older or overweight dogs have at least one lipoma. In dogs, lipomas usually occur in the trunk or upper limbs. Lipomas are also found less commonly in cattle and horses, and rarely in cats and pigs. However, a pedunculated lipoma can cause entrapment and torsion of the intestine in horses, causing necrosis, colic, and possibly death. The intestine becomes wound around the stalk of the lipoma and loses blood supply.
Other conditions involving lipomas
Lipomatosis is believed to be a hereditary condition in which multiple lipomas are present on the body.
Benign symmetric lipomatosis (Madelung disease) is another condition involving lipomatosis. It nearly always appears in middle-aged males after many years of alcoholism. But, non-alcoholics and females can also be affected.
- Bancroft LW, Kransdorf MJ, Peterson JJ, O'Connor MI (October 2006). "Benign fatty tumors: classification, clinical course, imaging appearance, and treatment". Skeletal Radiol. 35 (10): 719–33. doi:10.1007/s00256-006-0189-y. PMID 16927086.
- 'Obesity Gene' Causes Cancer of Fat Tissue, Schepens Scientists Find Schepens Eye Research Institute (Harvard Medical School affiliate). April 26, 2000
- Lipomas at eMedicine
- James, William D.; Berger, Timothy G.; Elston, Dirk M. (2005). Andrews' Diseases of the Skin: Clinical Dermatology (10th ed.). London: Elsevier. ISBN 0-7216-2921-0.
- James, William D.; Berger, Timothy G.; Elston, Dirk M. (2011). Andrews' Diseases of the Skin: Clinical Dermatology (11th ed.). London: Elsevier. ISBN 9781437703146.
- Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. p. 1838. ISBN 1-4160-2999-0.
- Crowson MG, Symons SP, Chen JM. Left cerebellopontine angle lipoma with mild brainstem compression in a 13-year-old female. Otology& Neurotology. Epub 2013 March 15.
- Wallace D (December 1976). "Lipoma of the corpus callosum". J Neurol Neurosurg Psychiatry. 39 (12): 1179–85. doi:10.1136/jnnp.39.12.1179. PMC 492562. PMID 1011028.
- Salam GA (March 2002). "Lipoma excision". Am Fam Physician 65 (5): 901–4. PMID 11898962.
- Buisson P, Leclair MD, Jacquemont S, et al. (September 2006). "Cutaneous lipoma in children: 5 cases with Bannayan-Riley-Ruvalcaba syndrome". J. Pediatr. Surg. 41 (9): 1601–3. doi:10.1016/j.jpedsurg.2006.05.013. PMID 16952599.
- Gujrati M, Thomas C, Zelby A, Jensen E, Lee JM (August 1998). "Bannayan-Zonana syndrome: a rare autosomal dominant syndrome with multiple lipomas and hemangiomas: a case report and review of literature". Surg Neurol 50 (2): 164–8. doi:10.1016/S0090-3019(98)00039-1. PMID 9701122.
- Lipoma—topic overview at webmd.com
- Hakim E, Kolander Y, Meller Y, Moses M, Sagi A (August 1994). "Gigantic lipomas". Plast. Reconstr. Surg. 94 (2): 369–71. doi:10.1097/00006534-199408000-00025. PMID 8041830.
- Terzioglu A, Tuncali D, Yuksel A, Bingul F, Aslan G (March 2004). "Giant lipomas: a series of 12 consecutive cases and a giant liposarcoma of the thigh". Dermatol Surg 30 (3): 463–7. doi:10.1111/j.1524-4725.2004.30022.x. PMID 15008886.
- Leffell DJ, Braverman IM (August 1986). "Familial multiple lipomatosis. Report of a case and a review of the literature". J. Am. Acad. Dermatol. 15 (2 Pt 1): 275–9. doi:10.1016/S0190-9622(86)70166-7. PMID 3745530.
- Toy BR (October 2003). "Familial multiple lipomatosis". Dermatol. Online J. 9 (4): 9. PMID 14594582.
- Arlotta P, Tai AK, Manfioletti G, Clifford C, Jay G, Ono SJ. (May 2000). "Transgenic mice expressing a truncated form of the high mobility group I-C protein develop adiposity and an abnormally high prevalence of lipomas". J Biol Chem. 275 (19): 14394–400. doi:10.1074/jbc.M000564200. PMID 10747931.
- Signorini M, Campiglio GL (March 1998). "Posttraumatic lipomas: where do they really come from?". Plast. Reconstr. Surg. 101 (3): 699–705. doi:10.1097/00006534-199803000-00017. PMID 9500386.
- Aust MC, Spies M, Kall S, Jokuszies A, Gohritz A, Vogt P (2007). "Posttraumatic lipoma: fact or fiction?". Skinmed 6 (6): 266–70. doi:10.1111/j.1540-9740.2007.06361.x. PMID 17975353.
- "Lipoma removal surgery". Retrieved 2010-07-26.
- Dalal KM, Antonescu CR, Singer S (March 2008). "Diagnosis and management of lipomatous tumors". J Surg Oncol 97 (4): 298–313. doi:10.1002/jso.20975. PMID 18286473.
- Al-basti HA, El-Khatib HA (2002). "The use of suction-assisted surgical extraction of moderate and large lipomas: long-term follow-up". Aesthetic Plast Surg 26 (2): 114–7. doi:10.1007/s00266-002-1492-1. PMID 12016495.
- Bechara FG, Sand M, Sand D, et al. (2006). "Lipolysis of lipomas in patients with familial multiple lipomatosis: an ultrasonography-controlled trial". J Cutan Med Surg 10 (4): 155–9. PMID 17234112.
- Thompson WM (1 April 2005). "Imaging and findings of lipomas of the gastrointestinal tract". AJR Am J Roentgenol 184 (4): 1163–71. doi:10.2214/ajr.184.4.01841163. PMID 15788588.
- Taylor AJ, Stewart ET, Dodds WJ (1 December 1990). "Gastrointestinal lipomas: a radiologic and pathologic review". AJR Am J Roentgenol 155 (6): 1205–10. doi:10.2214/ajr.155.6.2122666. PMID 2122666.
- Milgram JW (1990). "Malignant transformation in bone lipomas". Skeletal Radiol. 19 (5): 347–52. doi:10.1007/BF00193088. PMID 2165632.
- Lowe BA, Brewer J, Houghton DC, Jacobson E, Pitre T (May 1992). "Malignant transformation of angiomyolipoma". J. Urol. 147 (5): 1356–8. PMID 1569683.
- Goldblum, John R.; Weiss, Sharon W.; Enzinger, Franz M. (2008). Enzinger and Weiss's soft tissue tumors (5th ed.). Mosby Elsevier. ISBN 0-323-04628-2.
- Fletcher, C.D.M., Unni, K.K., Mertens, F. (2002). Pathology and Genetics of Tumours of Soft Tissue and Bone. World Health Organization Classification of Tumours 4. Lyon: IARC Press. ISBN 92-832-2413-2.
- E.J. Mayeaux Jr. (2009). The Essential Guide to Primary Care Procedures, p.386, Wolters Kluwer Health. ISBN 978-0-7817-7390-4.
- Adipose Tissue Tumors The Merck Veterinary Manual, (9th ed.)
- Lipomas Veterinary & Aquatic Services Department, Purina
- Lipoma Virginia Polytechnic Institute and State University
- Lipomas (Fatty Tumors) Veterinary Q & A
- The Merck Veterinary Manual. Merial. 9th Edition. ISBN 0911910506.
- Lipomas at eMedicine
- Illustration from University of Connecticut Health Center
- Esophageal Lipomatosis MedPix Images from Uniformed Services University of the Health Sciences
- Lipoma images from DermAtlas
- humpath #2626
- List of possible treatment options