Angiolipoma – Causes, Symptoms, Diagnosis, Treatment

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Angiolipoma is a rare benign neoplasm composed of mature fatty tissue and multiple small abnormal blood vessels. Infiltrating mediastinal angiolipoma is an extremely rare tumor associated with delayed diagnosis.

Angiolipomas are benign tumors that usually occur in the subcutaneous layer of the trunk and extremities. They rarely occur on the spine. Spinal angiolipomas commonly occur on the midthoracic spine and are located on the dorsolateral aspect of the cord. The symptoms of spinal angiolipomas usually appear gradually because of the progressive compression of the cord. However, sometimes, symptoms can arise rapidly because of intratumoral hemorrhage and venous thrombosis. Most spinal angiolipomas have a good prognosis following surgical resection, and noninfiltrating tumors are relatively easily dissected from the dura and adjacent structures because of the good encapsulation of the mass[. In contrast, infiltrating tumors are entirely or partially unencapsulated.

Types of Angiolipoma

Angiolipomas are classified as either noninfiltrating or infiltrating. Noninfiltrating angiolipomas are more common,, and are relatively easily dissected from the dura. However, if MRI suggests a highly vascular lesion, preoperative angiography and embolization can be performed. Noninfiltrating tumors are usually located in the posterior epidural space, and infiltrating tumors are generally located in the anterior epidural space. Infiltrating angiolipomas can also invade the vertebral body and paraspinal area. Sometimes, infiltrating angiolipomas may be mistaken for malignant tumors because of the invasion of surrounding tissue,.

  • Gastric angiolipomas – These occur in the stomach. According to one review, only four cases of gastric angiolipoma have been reported as of mid-2017. This type of angiolipoma might result in additional symptoms, like gastrointestinal bleeding and anemia.
  • Spinal angiolipomas – These occur in the thoracic epidural space of the spine. This is the space located just outside the spinal cord lining of the upper and lower back. Fewer than 200 casesTrusted Source have been reported as of mid-2017. A spinal angiolipoma can result in weakness or tingling sensations in the body or problems with balance.
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Pathology

The tumor is composed of mature adipose fat cells and vascular components, and to be classified as a SAL, more than 50% of the cells must be fat cells.[rx,rx,rx] The benign nature of the tumor has also been described as a mixture of developed adipocytes and dividing miniature vessels containing fibrin, as well as a neoplasm or a congenital malformation of pluripotent mesenchymal stem cell origin.[rx,rx] The tumor has been described, in certain cases, to deteriorate more rapidly resulting in hemorrhage, thrombosis, vascular steal phenomena, or expand into a larger tumor volume.[rx,rx,rx,rx] In certain cases of SAL, significant amounts of smooth muscle can be appreciated, further classifying the tumor as an angiomyolipoma. Without an adventitia, the smooth muscle may mesh into the surrounding tissue, or into cartilage or osteoid tissue in the vicinity.[rx] The tumor can result in eroded pedicles, trabeculation of vertebral bodies or mediastinum, and/or spinal cord compression.[rx,rx] In certain cases, the trabeculations present as vertical striations of the vertebral bodies, which is also characteristic of spinal hemangiomas.[rx]

Causes of Angiolipoma

Some angiolipomas have no known cause. In other cases, they can be caused by:

  • Genetics – If a parent or sibling has an angiolipoma, a person is more likely to have them, as well.
  • Injury – Angiolipomas can result from blunt trauma, such as a previous car accident.
  • Antiretroviral therapies – Medications used to reduce the incidence of viruses, such as HIV, can make angiolipomas more likely.
  • Diabetes – A person with diabetes is more likely to develop angiolipomas.

Symptoms of Angiolipoma

Unlike other lipomas, angiolipomas may feel tender or even painful. The skin over the angiolipoma is usually healthy. A person can usually feel it and may notice several other lesions around the area.

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Angiolipoma lumps usually have the following symptoms:

  • Circumscribed subcutaneous mass
    • Frequently multiple
    • Rarely greater than 2 cm
    • Infiltrating intramuscular tumors are considered intramuscular hemangiomas
    • Spinal angiolipoma is regarded as a distinct entity
  • These are composed of mature fat with numerous small blood vessels
  • The vascular component may be patchy
    • Frequently accentuated in subcapsular area
    • Vessels are predominantly capillaries
    • Fibrin thrombi are almost always present
    • Fibrosis may be associated with a vascular component
  • Cellular variant
      • Defined as having 95% cellular, angiomatous tissue
      • Spindle cells are abundant in cellular areas
      • There is only mild pleomorphism
      • Mitotic figures are inconspicuous
    • These have been associated with usual angiolipomas in the same patient
  • round or spherical in appearance
  • soft to touch
  • a doughy or rubbery texture when touched
  • easily moved
  • often occurring in multiples

Diagnosis of Angiolipoma

Diagnostic Criteria

  • Circumscribed subcutaneous mass
    • Frequently multiple
    • Rarely >2 cm
    • We consider infiltrating intramuscular tumors to be intramuscular hemangiomas
    • We consider spinal angiolipoma to be a distinct entity
  • Composed of mature fat with numerous small blood vessels
    • Vascular component may be patchy
      • Frequently accentuated in subcapsular area
    • Vessels are predominantly capillaries
    • Fibrin thrombi are almost always present
    • Fibrosis may be associated with vascular component
    • Cellular variant
      • Defined as 95% cellular, angiomatous tissue
      • Spindle cells abundant in cellular areas
      • Only mild pleomorphism
      • Mitotic figures inconspicuous
      • Have been associated with usual angiolipomas in the same patient
      • No clinical significance

Other diagnostic tests useful in confirming a diagnosis include:

  • Biopsy – A doctor takes a small piece of the angiolipoma and sends it to a laboratory for testing. This may be done to rule out the possibility of cancer or to differentiate an angiolipoma from another type of lipoma. In general, an angiolipoma has a higher degree of vascularity, or blood vessel development, than a lipoma.
  • MRI and CT scan – Your doctor may use an MRI or CT scan to make a diagnosis. This may be the case if your doctor suspects that the growth is actually a cancerous condition called liposarcoma.

Treatment

Angiolipomas are usually easy to remove with surgery, though removal can be complicated with growths in deeper tissue, such as the spine.

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Corticosteroid injections can shrink or get rid of an angiolipoma by causing the fat cells to shrink and die. This involves injecting a local anesthetic and steroid mixture into the lipoma. Sometimes, a doctor must administer multiple injections.

New methods under development are supposed to remove the lipomas without scarring. One is removal by injecting compounds that trigger lipolyses, such as steroids or phosphatidylcholine.[rx][rx] Other potential methods based on tissue-targeted heating include cauterization, electrosurgery, and harmonic scalpel.[rx]

After removal, a lipoma, usually does not return in the same place.[rx]

Differential Diagnosis

  • The typical angiolipoma can be confused only with an ordinary lipoma
Kaposi SarcomaCellular Angiolipoma
Patches, plaques or nodulesSubcutaneous nodules
Associated with HIVAssociated with typical angiolipomas
Poorly localizedCircumscribed
Cytologic atypiaNo atypia
Slits with red cell extravasationSmall vessels with fibrin thrombi

 

Spindle Cell HemangioendotheliomaCellular Angiolipoma
Poorly localizedCircumscribed
Frequent cavernous vesselsSmall vessels with fibrin thrombi
Biphasic spindle and epithelioid cellsSmall vessels and spindle cells
Not associated with typical angiolipomasFrequently associated with typical angiolipomas

 

AngioleiomyomaCellular Angiolipoma
Infrequent fat component (but may be seen)Fat component focal but present
Large thick walled vesselsVascular component is predominantly capillaries
No fibrin thrombiFibrin thrombi

 

AngiomyolipomaAngiolipoma
Myoid componentNo myoid component
Large thick walled vesselsVascular component is predominantly capillaries
HMB45 positiveHMB45 negative

References