[1021] Immunohistochemical and Mutational Analysis of FOXL2 in Uterine Tumors Resembling Ovarian Sex-Cord Tumors.

Sarah Chiang, Blake Gilks, David G Huntsman, Esther Oliva. Massachusetts General Hospital, Boston; BC Cancer Agency, Vancouver, BC, Canada

Background: Somatic mutations in the FOXL2 gene have recently been described in adult granulosa cell tumors (AGCTs). The FOXL2 C>G mutation, which converts cysteine to tryptophan, is present in the vast majority of AGCTs. Uterine tumors resembling ovarian sex-cord tumors (UTROSCTs) are rare uterine neoplasms with predominant epithelial-like patterns that morphologically, immunohistochemically, and ultrastructurally resemble ovarian sex-cord tumors to variable degrees, particularly AGCTs. It is, however, unknown whether UTROSCTs express FOXL2 protein or harbor the same FOXL2 mutation as seen in AGCTs.
Design: Immunohistochemical stains for FOXL2 protein were performed on 16 UTROSCTs. Percentage of tumor cells with nuclear staining and intensity of staining were evaluated. Mutational analysis using a TaqMan real-time PCR-based allelic discrimination assay was performed on formalin-fixed, paraffin-embedded tissue from 22 UTROSCTs.
Results: Nuclear expression of FOXL2 was present in 4 of 16 UTROSCTs. Percentage of tumor cells with FOXL2 expression ranged from <10% to 40%. Intensity of nuclear staining ranged from 1+ (2 cases) to 3+ (1 case). Mutational analysis was successful in 14 of 22 tumors, but FOXL2 mutation was not identified in any of them.
Conclusions: Although a subset of UTROSCTs show focal FOXL2 nuclear expression by immunohistochemistry, FOXL2 is not mutated in these tumors. Despite overlapping features of UTROSCTs and AGCTs, a strong histogenetic relationship between these two tumor categories cannot be inferred from these results. Thus, UTROSCTs remain in the uncertain histogenesis category of tumors as currently placed by the latest WHO classification.
Category: Gynecologic & Obstetrics

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 191, Wednesday Afternoon


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