Solitary fibrous tumour of the female genital tract: a clinicopathological analysis of 25 cases.

AIMS: Solitary fibrous tumour (SFT) is an uncommon spindle cell neoplasm of fibroblastic origin, first described as a tumour of the pleura and now well established at extrapleural sites. However, SFT in the female genital tract is rare and therefore not fully characterised. Here, we describe a series of 25 SFTs arising throughout the gynaecological tract, including the vulva (14 cases), vagina (one), cervix (one), uterus (six), ovary (two), and fallopian tube (one).

METHODS AND RESULTS: The tumours showed classic histology as well as known variant morphological features, including a fatty component, diffuse stromal hyalinisation, myxoid stroma, and giant-cell angiofibroma-like features. Eleven (11/25, 44%) were considered to be histologically malignant on the basis of mitotic counts of ≥4 per 10 high-power fields. Follow-up data were available for nine (3-56 months; mean 25 months). Six patients are alive with no evidence of disease, and three are alive with disease. Both SFT and other spindle cell lesions of the gynaecological tract were stained for STAT6. Ninety per cent of SFTs showed nuclear expression of STAT6. The majority of other tumour types were negative for STAT6, except for a subset of inflammatory myofibroblastic tumours (1/3; 33%), fibroma/thecoma (3/56; 5%), and sclerosing stromal tumour (1/3; 33%), which showed weak/focal staining.

CONCLUSION: Gynaecological SFT can be diagnosed reliably with careful morphological evaluation and judicious use of immunohistochemical stains, and should be considered in the diagnostic workup of spindle cell tumours of unclear lineage in the female genital tract.