Pathology of Angiomyofibroblastoma [Infographic]

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Pathology of Angiomyofibroblastoma

Dr Sampurna Roy MD 2023

Angiomyofibroblastoma: [ Pathology Infographic ]

Angiomyofibroblastoma is a rare myofibroblastic tumour of superficial soft tissues described by Fletcher et al. in 1992.

Age: Usually occurs in young to middle aged females in their reproductive years (25 to 50 years).

Rare cases occur in males with the age ranging from 40 to 80yrs.

Site:

Occurs in the vulvovaginal region of women. Rare cases have been reported in the female urethra and fallopian tube.

Clinically the lesion may be mistaken for Bartholin's cyst or inguinal hernia.

In males, the tumour may occur in the scrotum or paratesticular tissues.

Clinically, the lesion may present as a scrotal mass, hernia or hydrocele.

Gross appearance:

The tumours are mostly well circumscribed, round, ovoid, or lobulated masses with a soft to rubbery consistency measuring 0.5-12 cm in maximum dimension.

The cut surface has a greyish-brown homogeneous appearance with no hemorrhage or necrosis.

In some cases the tumour may present as a gelatinous mass which is completely encapsulated by a thin fibrous capsule.

Microscopic features:

Tumour is characterized by alternating hypercellular and hypocellular edematous areas with abundant blood vessels.

Cellularity is quite variable and is related to the vascularity.

The hypercellular areas showed a perivascular proliferation of bland round, oval or spindle-shaped cells with eosinophilic cytoplasm.

There may be hyperchromatic degenerative nuclear changes.

These cells are often arranged in small epithelioid nests and cords.

Spindle cells form loosely organizing short fascicles.

The proliferating vessels are thin-walled and capillary-sized.

Perivascular fibrosis or sclerosis is often present.

The cells are set in a loose edematous or fibrocollagenous background.

The stroma is Alcian blue negative.

A variable number were binucleated or multinucleated cells are present.

Intralesional fat tissues are observed. In rare cases, adipose cells predominate and such tumours have been classified as the "lipomatous" variant of angiomyofibroblastoma.

Rarely the tumour may show prominent mitotic activity (3/10 high-power field). There are no abnormal mitotic figures.

A single case of sarcomatous transformation (angiomyofibrosarcoma) has been described.

Immunohistochemistry:

The stromal cells are consistently positive for vimentin and desmin (strongly and diffusely).

Muscle specific actin - negative or weakly positive. Alpha-smooth muscle actin - focally positive or negative.

Myosin, cytokeratins, S-100 protein and von Willebrand factor are negative

Both estrogen and progesterone (some cases) receptors may be diffusely expressed in the tumour, suggestive of the sex steroid-dependency of this tumour.

Differential diagnosis:

Aggressive Angiomyxoma: Angiomyofibroblastoma can be distinguished from aggressive angiomyxoma by its circumscribed non-infiltrative borders , much higher cellularity, more numerous blood vessels, frequent presence of plump stromal cells, minimal stromal mucin, and rarity of erythrocyte extravasation.

In angiomyofibroblastoma cells may aggregate or form masses around blood vessels.

The cells have a myoepithelial appearance.

Cellular Angiofibroma: Cellular angiofibroma: a benign neoplasm distinct from angiomyofibroblastoma and spindle cell lipoma.

Superficial Angiomyxoma: Superficial angiomyxoma (cutaneous myxoma): a clinicopathologic study of 17 cases arising in the genital region.

Superficial cervicovaginal myofibroblastoma: Superficial cervicovaginal myofibroblastoma: fourteen cases of a distinctive mesenchymal tumor arising from the specialized subepithelial stroma of the lower female genital tract.

Spindle cell lipoma ; Myxoid liposarcoma ; myxoid neurofibroma.