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The case of a 65‐year‐old female patient who has had a large right vulval mass for over 30 years is reported here. The mass was excised, but the hypocellular mesenchymal tumour was difficult to classify histologically. On further specialist assessment, it was found to be identical to the recently recognised distinctive prepubertal vulval fibroma. These are very rarely reported in children, and till now, has never been reported in an adult.
A 65‐year‐old postmenopausal woman was referred with a painless vulval swelling that the patient had had for over 30 years. It had gradually increased in size over the past few years, causing discomfort during sexual intercourse and when riding a bicycle. It also caused an embarrassing bulge in her leotard as she taught yoga. She remained fit and healthy. There was no previous medical history of note. Examination revealed a 9 cm×5 cm×5 cm soft, non‐tender, non‐reducible right vulval mass with normal skin fully mobile over it. It was partially fixed to underlying structures (fig 11).
MRI of the pelvis and perineum revealed a diffuse abnormality causing enlargement of the right side of the vulva and perineum extending from the infrapubic region to the anal margin. There was extensive signal change within the perineal fat. No discrete mass was seen and no lymphadenopathy was detected.
An initial incisional biopsy suggested that the unusual vulval mass was a benign smooth muscle harmatoma without atypia or malignancy. Surgical excision of the mass was performed with excellent cosmetic results followed by further histological assessment. This showed that the lesion was composed of bland fibroblastic cells associated with abundant stromal collagen, which seemed to be infiltrating and replacing large parts of the submucosal tissue, entrapping nerves, vessels and adipose tissue and extensively disrupting normal pre‐existing smooth muscle (fig 22).). The cellularity was increased above the appearances, normal at this site. The individual spindle cells had pale distinct cytoplasm with bland nuclei and no conspicuous mitotic activity. Immunostains showed CD34 positivity whereas S‐100 protein and smooth muscle actin were negative. The tumour stained oestrogen and progesterone receptor negative. As the lesion was difficult to classify, a specialist histological opinion was sought. Morphologically, this lesion was considered to be identical to a distinctive vulval fibroma of so‐called prepubertal type.
This represents the first report in the literature of a distinctive vulval fibroma of the prepubertal type in an adult. Moreover, our patient was postmenopausal. This mesenchymal tumour has only recently been recognised by Iwasa and Fletcher1 who analysed a series of 11 prepubertal girls with an age range of 4–12 years. As in their series, the tumour was hypocellular and poorly marginated consisting of bland spindle‐shaped cells and stromal collagen. There was diffuse infiltration between pre‐existing local tissues such as neural and smooth muscle. Cytological atypia and mitotic hyperactivity were absent. The tumour stained for CD34 but not for S‐100 or smooth muscle actin.
The main differential diagnosis is with a desmoplastic fibroblastoma or collagenous fibroma, but this usually forms a discrete mass with more distinctive larger stellate fibroblastic cells and does not stain for CD34.2,3 The other differential diagnosis included a number of mesenchymal and tumour‐like lesions, the most important of which was aggressive angiomyxoma. This tumour shares some histological features with vulval fibroma but, unlike the latter, has a diffusely myxoid stroma with delicate collagen fibrils and perivascular smooth muscle proliferation. Vulval fibroma, by contrast, contains short bundles of thick, wavy collagen, myxoid change is not so diffuse and there is no perivascular smooth muscle proliferation. The cells of aggressive angiomyxoma are immunoreactive for desmin whereas those of vulval fibroma are not. Cytogenetics can be used to differentiate the two, but this is not widely available and routine histological and immunohistochemical examinations can differentiate between the two in most cases.4
Other differential diagnosis included angiomyofibroblastoma, cellular angiofibroma, fibroepithelial stromal polyp, neurofibroma and desmoplastic fibroblastoma. Angiomyofibroblastoma is a benign well‐circumscribed vulval tumour with a thin fibrous tissue capsule, variable cellularity, prominent thin‐walled blood vessels and desmin positive tumour cells grouped around vessels. Cellular angiofibroma is a relatively well‐demarcated tumour, which is invariably more cellular than vulvar fibroma and often contains adipocytes towards the periphery of the tumour. The vessels are more numerous and usually hyalinised. Neurofibroma occurs rarely as a solitary lesion at this site. Although, the stroma can appear similar to vulval fibroma the spindle cells are tapered with wavy, buckled nuclei and show consistent S‐100 immunoreactivity. Fibroepithelial stromal polyps can rarely have a myxoid stroma and contain stellate‐shaped spindle cells with multinucleate cells, which extend to the base of the epithelium. The lesional cells are oestrogen and progesterone receptor positive.
Although non‐aggressive, prepubertal vulval fibromas have been shown to recur with incomplete excision. A complete surgical excision was desirable in this patient but this was technically impossible because of the extent of the tumour and the desired cosmetic results. Since our patient had a slow‐growing benign tumour re‐excision is unlikely to be required in this 65‐year‐old. The patient had been counselled appropriately before surgery and was made aware of the possibility of recurrence. She remains well about 20 months after surgery with no sign of recurrence of the lesion. She remains under biannual surveillance.
We thank Professor C D M Fletcher, Department of Pathology, Harvard Medical School, Boston, Massachusetts, USA for providing a specialist opinion on the histological slides.
Competing interests: None declared.