Lipoma

Variant: Angiolipoma

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

CD34 and CD31 stain endothelium of vessels
Genetic studies have generally shown no abnormalities
- Contrasts with ordinary lipomas

Kaposi Sarcoma	Cellular Angiolipoma
Patches, plaques or nodules	Subcutaneous nodules
Associated with HIV	Associated with typical angiolipomas
Poorly localized	Circumscribed
Cytologic atypia	No atypia
Slits with red cell extravasation	Small vessels with fibrin thrombi

Spindle Cell Hemangioendothelioma	Cellular Angiolipoma
Poorly localized	Circumscribed
Frequent cavernous vessels	Small vessels with fibrin thrombi
Biphasic spindle and epithelioid cells	Small vessels and spindle cells
Not associated with typical angiolipomas	Frequently associated with typical angiolipomas

Angioleiomyoma	Cellular Angiolipoma
Infrequent fat component (but may be seen)	Fat component focal but present
Large thick walled vessels	Vascular component is predominantly capillaries
No fibrin thrombi	Fibrin thrombi

Angiomyolipoma	Angiolipoma
Myoid component	No myoid component
Large thick walled vessels	Vascular component is predominantly capillaries
HMB45 positive	HMB45 negative

Common lesion
Age range 16-84 years, median 24 years
- Usually adult onset
Most common on arms and trunk
- Uncommon on legs, hands, head, face and neck
Frequently multiple
- Commonly 2-4 nodules
- Occasionally innumerable nodules
  - Multiple cases may be familial
May be painful
- One of the five painful tumors of the skin (see Lists at left)
- Very difficult to treat if too many nodules to resect
Recurrences very rare

Hunt SJ, Santa Cruz DJ, Barr RJ. Cellular angiolipoma. Am J Surg Pathol. 1990 Jan;14(1):75-81.
Sciot R, Akerman M, Dal Cin P, De Wever I, Fletcher CD, Mandahl N, Mertens F, Mitelman F, Rosai J, Rydholm A, Tallini G, Van den Berghe H, Vanni R, Willen H. Cytogenetic analysis of subcutaneous angiolipoma: further evidence supporting its difference from ordinary pure lipomas: a report of the CHAMP Study Group. Am J Surg Pathol. 1997 Apr;21(4):441-4.
Lin JJ, Lin F. Two entities in angiolipoma. A study of 459 cases of lipoma with review of literature on infiltrating angiolipoma. Cancer. 1974 Sep;34(3):720-7.
Howard WR, Helwig EB. Angiolipoma. Arch Dermatol. 1960 Dec;82:924-31.
Hattori H. Epidural angiolipoma is histologically distinct from its cutaneous counterpart in the calibre and density of its vascular component; a case report with review of the literature. J Clin Pathol. 2005 Aug;58(8):882-3.
Cina SJ, Radentz SS, Smialek JE. A case of familial angiolipomatosis with Lisch nodules. Arch Pathol Lab Med. 1999 Oct;123(10):946-8.