Soft tissue

Adipose tissue tumors

Lipoma and variants

Angiolipoma


Resident / Fellow Advisory Board: Josephine K. Dermawan, M.D., Ph.D.
Deputy Editor-in-Chief: Borislav A. Alexiev, M.D.
Laura Warmke, M.D.
Jeanne Meis, M.D.

Last author update: 9 December 2021
Last staff update: 9 December 2021

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PubMed Search: Angiolipoma[TI] soft tissue

Laura Warmke, M.D.
Jeanne Meis, M.D.
Page views in 2021: 16,893
Page views in 2022 to date: 14,032
Cite this page: Warmke L, Meis J. Angiolipoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueadiposeangiolipoma.html. Accessed August 14th, 2022.
Definition / general
  • Benign, soft tissue tumor consisting of mature adipose tissue and clusters of thin walled vessels, often containing intraluminal fibrin thrombi
  • First described in 1912 by Bowen (Hum Pathol 1981;12:739)
  • Established as a distinct entity in 1960 by Howard and Helwig (Arch Dermatol 1960;82:924)
Essential features
  • Mature adipocytes
  • Clusters of capillary sized vessels
  • Fibrin thrombi in vessels
Terminology
  • Cellular angiolipoma (morphologic variant)
ICD coding
Epidemiology
  • Relatively common in young adults (Arch Dermatol 1960;82:924)
  • Usually appears in late second to early third decade of life
  • Rare in children or adults > 50 years
  • Male predominance
Sites
  • Forearm, trunk and upper arm common sites
  • Rare on scalp or face
  • Intramuscular hemangiomas represent different lesions (Arch Surg 1980;115:281)
  • So called angiolipomas of parenchymal organs and central nervous system represent different lesions containing larger vessels (World Neurosurg 2018;114:264)
Pathophysiology
  • Unknown
  • Association between sporadic angiolipoma and overlying cutaneous capillary malformation has been reported (Am J Clin Dermatol 2008;9:389)
Etiology
Clinical features
  • Frequently present as multiple subcutaneous small nodules
  • Nodules are usually tender or painful
  • There is no correlation between degree of vascularity and intensity of pain (Hum Pathol 1981;12:739)
Diagnosis
  • Tender, often multiple subcutaneous nodules (Arch Dermatol 1960;82:924)
  • Mature adipocytes
  • Clusters of capillary sized vessels
  • Intraluminal fibrin microthrombi
Radiology description
  • Ultrasound (Skeletal Radiol 2012;41:1055):
    • Oval shaped
    • Well defined margins
    • Hyperechoic lesions compared to muscle
    • Color Doppler flow present in < 25% of cases
  • CT (Arch Pathol Lab Med 2017;141:862):
    • Heterogeneous appearance
    • Mixed fat and soft tissue density
  • MRI (Skeletal Radiol 2018;47:859):
    • Fatty component shows high signal intensity on T1 weighted images and signal suppression on fat suppressed images
    • Vascular component shows areas of low signal intensity on T1 weighted images and high signal intensity on fat suppressed T2 weighted images
Radiology images

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Gastric angiolipoma

Prognostic factors
Case reports
Treatment
Clinical images

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Familial multiple angiomatosis

Familial multiple angiomatosis

Soft nodular mass

Multilobular

Gross description
Gross images

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Lesion and its microscopic appearance

Microscopic (histologic) description
  • Consists of mature adipose tissue and branching capillary sized vessels
  • Thin walled vessels often contain bright pink fibrin thrombi
  • Vascularity is more prominent in the periphery (Hum Pathol 1981;12:739)
  • Well formed capillaries often have a lobular arrangement
  • Occasionally, few thin fibrous septae present
  • Proportion of adipocytes and vessels varies
  • No nuclear atypia in the adipocytic or vascular component
  • Endothelial cells are bland and uniform
  • Morphologic variant: cellular angiolipoma (vessels predominate)
Microscopic (histologic) images

Contributed by Laura Warmke, M.D. and Jeanne Meis, M.D.
Angiolipoma

Angiolipoma

Subcutaneous angiolipoma

Subcutaneous angiolipoma

Cluster of vessels

Cluster of vessels

Mature adipose tissue

Mature adipose tissue

Peripheral vessels

Peripheral vessels


Mature adipose tissue with vessels

Mature adipose tissue with vessels

Well circumscribed nodule

Well circumscribed nodule

Vascular component

Vascular component

Fibrin thrombi

Fibrin thrombi

Intraluminal fibrin thrombi

Intraluminal fibrin thrombi



Cellular angiolipoma
Cellular angiolipoma

Cellular angiolipoma

Circumscription at lesion's periphery

Circumscription at lesion's periphery

Prominent spindle cell component

Prominent spindle cell component

Fibrin thrombi

Fibrin thrombi

Myxoid stromal change

Myxoid stromal change

Virtual slides

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Angiolipoma

Angiolipoma

Subcutaneous angiolipoma

Subcutaneous angiolipoma

Cytology description
  • Not clinically relevant
Immunofluorescence description
  • Fluorescein labeled antihuman fibrinogen demonstrates intense, irregularly homogeneous fluorescence of the fibrin thrombi (Hum Pathol 1981;12:739)
Positive stains
  • Immunohistochemical stains generally not needed for diagnosis (Arch Pathol Lab Med 2017;141:862)
  • S100 protein (focal to diffuse positivity in adipocytes)
  • ERG (vascular component)
  • CD31 (vascular component)
  • CD34 (vascular component)
  • CD61 (platelet marker highlights thrombi)
Negative stains
Electron microscopy description
  • Adipose tissue with central lipid droplet surrounded by thin rim of cytoplasm
  • Capillaries lined by one or more endothelial cells
  • Decreased number of Weibel-Palade bodies in endothelial cells (Hum Pathol 1981;12:739)
  • Endothelial cells frequently surrounded by pericytes
  • Variable numbers of fibrin thrombi within capillaries
Molecular / cytogenetics description
Molecular / cytogenetics images

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Karyotype of angiolipoma

Videos

Angiolipoma

Sample pathology report
  • Skin and subcutaneous tissue, left forearm, excision:
    • Angiolipoma (see comment)
    • Comment: Sections show an oval, well circumscribed lesion composed of mature adipose tissue with clusters of capillary sized vessels. Multiple fibrin microthrombi are identified with the lumen of the vessels, supporting the above diagnosis.
Differential diagnosis
  • Lipoma:
    • Mature adipose tissue
    • Lacks vascular component and fibrin thrombi
    • Various translocations of chromosome 12q or 6p
    • May mimic fat predominant angiolipoma
  • Intramuscular hemangioma:
    • Previously known as infiltrating angiolipoma
    • May have fatty overgrowth
    • Large, infiltrative lesion
    • Located deep in muscle (not subcutaneous tissue)
    • Large thick walled vessels present
  • Spindle cell hemangioma:
    • Multiple painful subcutaneous nodules in extremities
    • Cavernous vascular spaces
    • Cellular zones of spindled and epithelioid endothelial cells
    • Large calcified thrombi (phleboliths)
  • Angiomyolipoma:
    • Spindle cells that are HMB45+ smooth muscle cells
    • Large caliber and thick walled vessels
    • Rare in subcutaneous tissue
  • Kaposi sarcoma (distinguish from cellular angiofibroma):
    • Spindled endothelial proliferation
    • Extravasated red blood cells
    • HHV8+ endothelial cells
    • Lack of encapsulation
    • PAS+ hyaline globules instead of fibrin thrombi
  • Angiosarcoma (distinguish from cellular angiofibroma):
    • Nuclear atypia in endothelial cells
    • Aggressive, infiltrative growth
    • Mitotic activity and necrosis frequent
    • Loss of pericytic (perivascular smooth muscle) cells
    • Lack of fibrin thrombi
Board review style question #1

What is the most common anatomic location for sporadic angiolipoma?

  1. Face
  2. Forearm
  3. Lower extremity
  4. Retroperitoneum
Board review style answer #1
B. Forearm

Comment Here

Reference: Angiolipoma
Board review style question #2

Which of the following histologic features is associated with angiolipoma?

  1. Bundles of smooth muscle
  2. Cytologic atypia
  3. Fibrin thrombi
  4. Large, thick walled blood vessels
Board review style answer #2
C. Fibrin thrombi

Comment Here

Reference: Angiolipoma
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