Solitary Fibrous Tumor of the Female Genital Tract: A Clinicopathologic Analysis of 25 Cases

Abstract

Aims

Solitary fibrous tumor (SFT) is an uncommon spindle cell neoplasm of fibroblastic origin, first described as a tumor of the pleura and now well established at extrapleural sites. However, SFT in the female genital tract is rare and therefore not fully characterized.

Material and results

We describe a series of 25 SFTs arising throughout the gynecologic tract, including vulva (14 cases), vagina (1), cervix (1), uterus (6), ovary (2) and fallopian tube (1). The tumors demonstrated classic histology as well as known variant morphologic features, including those with a fatty component, diffuse stromal hyalinization, myxoid stroma, and giant cell angiofibroma-like features. Eleven (11/25, 44%) were considered histologically malignant based on mitotic counts ≥ 4 per 10 high-power field (HPF). Follow-up data was available for 9 (3 to 56 months; mean 25 months). Six patients are alive with no evidence of disease and three are alive with disease. SFT as well as other spindle cell lesions of the gynecologic tract were stained for STAT6. Ninety percent of SFTs showed nuclear expression of STAT6. The majority of other tumor types were negative for STAT6, except in a subset of inflammatory myofibroblastic tumors (1 of 3; 33%), fibroma/thecoma (3 of 56; 5%), and sclerosing stromal tumor (1 of 3; 33%) that demonstrated weak/focal staining.

Conclusion

Gynecologic SFT can be diagnosed reliably with careful morphologic evaluation and judicious use of immunohistochemical stains, and should be considered in the diagnostic workup of spindle cell tumors of unclear lineage in the female genital tract.

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