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Angiomyofibroblastoma is a rare, recently described, soft tissue tumour that occurs mainly, but not exclusively, in the vulval region of premenopausal women.1 We report a case arising in the vagina to draw the attention of pathologists to the fact that this rare neoplasm can occur outside the vulva.
A 54 year old woman, para 4 + 0, presented with a two year history of vaginal wall prolapse. Vaginal examination revealed a polypoid lesion on the anterior wall. Surgical removal and vaginal wall repair was performed.J Clin Pathol 2000;53:803–806
The surgical specimen consisted of surface mucosa with an underlying well circumscribed, firm, homogenous, white coloured lesion measuring 2.5 cm in maximum diameter. Histology showed unremarkable surface squamous epithelium. Deep to this, a well circumscribed but unencapsulated lesion was present. This contained numerous randomly distributed blood vessels, most of which were thin walled and capillary-like (fig 1A), whereas others had thick muscular walls. The surrounding stroma contained spindle shaped cells, some with wavy nuclei (fig 1B), and others with a plasmacytoid or epithelioid appearance. Occasional multinucleate cells were present (fig 1B). There was little or no nuclear pleomorphism and mitotic figures were not identified. In some areas there was a tendency for concentration of the stromal cells around blood vessels, although this was not a prominent feature. The stroma contained collagen fibres and was focally oedematous with some extravasation of red blood cells. Immunohistochemical staining showed diffuse positivity of stromal cells for vimentin (Dako, Copenhagen, Denmark). There was focal strong staining for desmin (Dako) and occasional cells were weakly positive for α smooth muscle actin (Sigma, Poole, Dorset, UK). There was no staining of stromal cells for S100 protein (Diagnostic Products Ltd, Abingdon, UK), AE1/AE3 (Dako), CD34 (Serotec, Oxford, UK), or factor VIII related antigen (Signet, Ontario, Canada). Staining for α smooth muscle actin, CD34, and factor VIII highlighted the vascular channels. There was diffuse strong positivity of stromal cells for the oestrogen receptor (ER) (Dako) and progesterone receptor (PR) (Dako).
Within the vulva the chief differential diagnosis of angiomyofibroblastoma is likely to be aggressive angiomyxoma. Angiomyofibroblastoma is distinguished from aggressive angiomyxoma by its circumscribed border and higher cellularity, by the frequent presence of plump stromal cells, and by a lesser degree of stromal myxoid change. Angiomyofibroblastoma of the vulva is almost always a benign lesion which, unlike aggressive angiomyxoma, shows little or no tendency for local recurrence. However, a single case with sarcomatous transformation has been described.2
Since the original description, angiomyofibroblastoma has been described outside the vulva, in the female urethra and in the male genital tract, and there have been occasional reports of this neoplasm arising in the vagina.3 In a report of 12 angiomyofibroblastomas, three had a vaginal location.3 When situated within the vagina, the main differential diagnoses are likely to be a leiomyoma with prominent vascularity or an angiomyoma. However, diffuse immunoreactivity with antidesmin antibodies would be expected in both these lesions, rather than the focal positivity seen in our present case.
The immunophenotype of angiomyofibroblastoma is not distinct but most cases are desmin positive and α smooth muscle actin negative. However, some are negative for desmin or positive for α smooth muscle actin. In this case, there was focal strong immunoreactivity for desmin, with only occasional cells staining with anti-α smooth muscle actin. Diffuse positivity for ER and PR was present and this has been described previously in vulval angiomyofibroblastoma.4 Although this raises the possibility that angiomyofibroblastoma is a hormone responsive neoplasm, positivity for ER and PR might simply be a reflection of the presence of these receptors normally in the subepithelial stromal cells of the vulva and vagina. It is probable that angiomyofibroblastoma in this region is derived from mesenchymal cells in the subepithelial myxoid stromal zone, which extends from the endocervix to the vulva.3 However, in a recent report this lesion has also been described in the fallopian tube.5