Cellular Angiofibroma

Definition

Circumscribed inguinal / perineal mass composed of bland spindled cells will prominent medium sized round vascular component

Well circumscribed subcutaneous nodule
- May have thin fibrous capsule
- Predominantly dermal in 10% of cases
- 2/51 cases reported with infiltration
Uniform distribution of bland spindle cells
- Moderately cellular
- Low mitotic rate, usually <1/10 hpf
- Occasional findings
  - Mitotic rate up to 10/10 hpf in 10% of cases
  - Intranuclear inclusions and nuclear grooves
  - Vague nuclear palisading
Prominent hyalinized round vessels
- Small to medium size
- Generally evenly distributed
- Staghorn vessels focal about 10% of cases
Fat admixed in 25% of cases
- May make up 50% of lesion
Fine collagen bundles
- Edematous to fibrous stroma
One series of 13 cases reported with atypia or sarcomatous transformation (Chen)
- Typical areas of cellular angiofibroma present
- 12/13 female
- 4 with atypia
  - Large hyperchromatic cells
  - 3 cases with scattered foci, 1 with a discrete nodule
- 9 with sarcomatous transformation
  - 2 with pleomorphic liposarcoma
  - 3 resembling atypical liposarcoma
    - MDM2 and CDK4 negative
  - 4 with abrupt transition to pleomorphic spindle cells
- p16 multifocal or diffuse in atypical cells or sarcomatoid areas
  - Scattered weak to negative in ordinary cellular fibroma areas
- Same behavior so far as usual cellular fibroma
  - No recurrences or metastases
May form a spectrum with spindle cell lipoma and Mammary Type Myofibroblastoma

Mammary Type Myofibroblastoma	Spindle Cell Lipoma	Cellular Angiofibroma
Usually diffuse collagen	Ropey collagen	Wispy collagen with prominent round vessels
Desmin positive	Desmin negative	Desmin variable

All are CD34 positive with loss of Rb due to 13q14 abnormalities; all are benign

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/last update: 5/27/07, 3/14/16