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Solitary Fibrous Tumor of the Vulva

Report of 2 Cases, Including a De Novo Dedifferentiated Solitary Fibrous Tumor Diagnosed After Molecular Demonstration of NAB2-STAT6 Gene Fusion

Tardío, Juan C., M.D., Ph.D.; Machado, Isidro, M.D., Ph.D.; Alemany, Isabel, M.D.; López-Soto, M. Victoria, M.D.; Nieto, M. Gema, Ph.D.; Llombart-Bosch, Antonio, M.D., Ph.D.

International Journal of Gynecological Pathology: November 2018 - Volume 37 - Issue 6 - p 547–553
doi: 10.1097/PGP.0000000000000464

Solitary fibrous tumor (SFT) is a neoplasm of fibroblastic lineage that has been documented in almost every anatomic location. Vulval SFT is very rare with only 10 cases reported to date. We present 2 additional SFTs located in the vulva, in adult women of 59 and 25 yr of age. The first showed a classic morphology and immunophenotype with uniform and strong STAT6 nuclear expression. The other one was a spindle-cell de novo dedifferentiated SFT with heterogeneous nuclear and cytoplasmic STAT6 staining, which could only be correctly diagnosed after molecular analysis with demonstration of a NAB2-STAT6 gene fusion. This genetic aberration is considered to represent the major pathogenic driver in SFT and is highly specific for this neoplasm. The differential diagnosis of vulval SFT is wide and varies depending on the histologic SFT subtype. Molecular analysis is mandatory for a correct diagnosis in cases without the characteristic histopathologic and immunophenotypical features.

Department of Pathology, University Hospital of Fuenlabrada (J.C.T., I.A.)

Department of Pathology, University Hospital Alcorcón Foundation (I.A.), Madrid

Department of Pathology, Molecular Biology (M.G.N.)

Department of Pathology (A.L.-B.), University of Valencia

Department of Pathology, Valencian Institute of Oncology (I.M.), Valencia, Spain

Department of Pathology, Enrique Cabrera National Hospital, Havana, Cuba (M.V.L.-S.)

The authors declare no conflict of interest.

Address correspondence and reprint requests to Juan C. Tardío, MD, PhD, Servicio de Anatomía Patológica, Hospital Universitario de Fuenlabrada, Camino del Molino 2, Fuenlabrada, Madrid 28942, Spain. E-mail:

©2018International Society of Gynecological Pathologists