A benign, well-circumscribed myofibroblastic neoplasm, usually arising in the pelviperineal region, especially the vulva, and apparently composed of stromale cells distinctive to this anatomic region. There may be morphologic overlap with cellular angiofibroma.
Angiomyofibroblastoma is uncommon, having an incidence comparable to aggressive angiomyxoma. These tumours arise predominantly in females, principally in adults between menarche and menopause. Around 10% of patients are postmenopausal. Convincing examples have not been described before puberty. Rare cases occur in males.
Sites of involvement
Virtually all cases arise in pelviperineal subcutaneous tissue, with the majority arising in the vulva. Around 10-15% of
cases are located in the vagina. Lesions in men occur in the scrotum or paratesticular soft tissue.
Most cases present as a slowly enlarging, painless, circumscribed mass. The most frequent preoperative diagnosis is
Bartholin’s gland ‘cyst’. The aetiology is unknown.
These lesions are well circumscribed but not encapsulated, with a tan/pink cut surface and a soft consistency. Necrosis is not seen. Most cases measure less than 5 cm in maximum diameter, although rare examples measuring up to 10 cm have been recognized.
Tumours are generally well demarcated by a thin fibrous pseudocapsule and, at low power, show varying cellularity with prominent vessels throughout. Vessels are mostly small, thin-walled and ecstatic and are set in an abundant loose, oedematous stroma. The tumour cells are round-to-spindle shaped with eosinophilic cytoplasm and typically are concentrated around vessels. Mitoses are rare. Binucleate and multinucleate tumour cells are common. Some cases show very plasmacytoid or epithelioid cytomorphology and rare examples show degenerative (‘ancient’) nuclear hyperchromasia and atypia. Around 10% of cases have a variably prominent well differentiated adipocytic component. In post-menopausal patients the stroma is often less oedematous and more fibrous and there may be hyalinization of vessel walls. Some cases show morphologic overlap with cellular angiofibroma and rare cases show morphologic overlap with aggressive angiomyxoma.
The majority of cases show strong and diffuse desmin positivity, while, at most, there is usually only focal positivity for
smooth muscle actin or pan-muscle actin. Desmin staining may be reduced or absent in postmenopausal cases. Tumour cells are consistently positive for oestrogen receptor and progesterone receptor, occasionally positive for CD34 and negative for S100 protein, keratin and fast myosin.
Tumour cells show fibroblastic or myofibroblastic features by electron microscopy.
Angiomyofibroblastoma is entirely benign and has never been reported to recur locally, even after marginal local
excision. There is one reported case of a clinically malignant counterpart of angiomyofibroblastoma.