Pathology of Aggressive Angiomyxoma

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Dr Sampurna Roy MD 2023

Aggressive angiomyxoma is a rare locally aggressive mesenchymal tumour which was first described by Steeper TA and Rosai J in 1983.

The tumour infiltrates locally and has a high risk of local recurrence after excision. Recurrence may occur many years after initial resection, hence a long term follow-up is required.

Recurrence of the tumour may be avoided by wide local excision.

The tumour has no potential to metastasize.

The patients are usually women, usually in the reproductive age group (second and third decade of life).

The tumour usually arises from the soft tissues of the pelvic region, perineum, vulva, buttock.

Rarely this tumour occurs in males in the scrotal region.

Aggressive angiomyxoma presents as a painless, poorly circumscribed gelatinous vulvar mass and clinically simulates a Bartholin gland cyst or an inguinal hernia.

Rarely, the tumour occurs in males in the scrotal region and presents as a scrotal mass, a hydrocele or a hernia.

On gross examination the tumours are lobulated, soft to rubbery, solid masses, usually more than 10 cms in diameter.

The cut surface reveals a glistening, soft homogeneous appearance.

Recurrent tumours show more prominent areas of hemorrhage and fibrosis

Histologically, the tumours are infiltrative, poorly circumscribed and are composed of bland round , spindle or stellate cells together with non-arborizing blood vessels of varied caliber, embedded in a hypocellular myxoid stroma.

The vessels are often thickened or hyalinized.

Thin bundles of smooth muscle fibres may be present in the stroma and around the vessels. Numerous foci of fresh hemorrhage are present around the blood vessels.

There is no evidence of atypia and any mitotic activity.

The backround stroma stains positively with alcian blue.

Immunohistochemical staining reveals that the tumour cells are immunoreactive for desmin, muscle specific actin and vimentin.

Estrogen and progesteron receptor protein may be positive.

The tumour cells are immunonegative for S100 protein, Factor VIII related antigen, carcinoembryonic antigen and cytokeratin.

The neoplastic cells of aggressive angiomyxoma exhibit fibroblastic and myofibroblastic features and appear to be hormonally influenced.

Cytogenetic analysis reveals chromosomal translocation involving chromosome 12 associated with rearrangement of the HMGIC gene.

HMGIC expression in aggressive angiomyxoma is of value in the distinction of difficult cases from its histological mimics.

Differential Diagnosis:

Angiomyofibroblastoma : This tumour is probably related to aggressive angiomyxoma and is derived from myofibroblasts and perivascular stem cells.

Unlike aggressive angiomyxoma this tumour exhibits the following features: Tumour size less than 8 cm , well circumscribed border, non infiltrative tumour, higher cellularity, prominent vascularity, plump stromal cells, minimal stromal mucin and rarely extravasation of red blood cells.

Cellular angiofibroma : Benign lesion with no evidence of recurrence.

Small lesion, less than 3cm in diameter.

The tumour is composed of spindle cells, bundles of collagen, hyalinized blood vessels and mature adipocyts, set in a loose cellular stroma.

Mitotic figures are conspicuous in some cases.

Immunohistochemistry reveals immunopositivity for CD34 and immunonegativity for actin, desmin and S100 protein.

Superficial angiomyxoma: Poorly circumscribed tumour with nodular growth pattern and composed of spindle cells set in a hypocellular stroma. Occasional binucleated and multinucleated cells are present. A mixed inflammatory infiltrate together with neutrophils are present in all cases. Cystic structures, strands of squamous epithelium or buds of basaloid cells are also identified.

Leiomyoma of vulva :The two variants commonly noted in vulva are myxoid and epithelioid.

In problematic cases immunostains play an important role in establishing the diagnosis.

Cervicovaginal myofibroblastoma: Moderate to highly cellular tumour composed of spindle and stellate cells. In areas, the tumour cells show lacelike or sievelike growth pattern, and vague fascicular pattern in more cellular areas. Abstract

The differential diagnosis also includes fibroepithelial polyps, intramuscular myxoma, spindle cell lipoma, myxoid neurofibroma, fibromatosis, myxoid liposarcoma, myxoid leiomyosarcoma, embryonal rhabdomyosarcoma and myxofibrosarcoma.