Molecular and Pathological Analysis of FOXL2 and TERT Promoter Mutations in Adult-Type Granulosa Cell Tumors of the Ovary: a Study of 64 Japanese Patients

Objective: Adult-type granulosa cell tumors of the ovary (aGCTs) show ambiguous morphology and may be misdiagnosed as other tumors. Recently, heterozygous FOXL2 C402G mutations and TERT promoter C228T mutation have been reported as diagnostic and prognostic biomarkers of aGCTs. The objective of this study was to identify the characteristics of true aGCT cohort using these biomarkers in 72 aGCT samples. Methods: FOXL2 and TERT promoter mutational statuses of 64 primary and matched 8 recurrent aGCT samples were assessed. Non-aGCTs were excluded by the combination of FOXL2 mutational analysis and the pathological review. The characteristics and prognosis of molecularly/pathologically confirmed aGCTs (MP-aGCTs) were analyzed. Results: Of 18 FOXL2 wild-type (WT) tumors, 3 were excluded as they were of other histotype. None of 20 samples with the FOXL2 C402G mutation include other histotype. Clinical stage and age were prognostic factors for recurrence. Of the 61 MP-aGCTs, 46 harbored FOXL2 C402G mutation (44 heterozygous, 2 homozygous/hemizygous) and 15 had WT FOXL2. The presence of the FOXL2 mutation was associated with a worse prognosis. The mutational status of the TERT promoter in MP-aGCTs was 10 heterozygous and 51 WT. The TERT promoter mutation was highly identified in older patients and in larger tumors but had no prognostic impact. Conclusion: This is the first study to clearly demonstrate its practical application of FOXL2 in the diagnosis of aGCTs. Application of the molecular analysis to a large aGCT cohort is crucial for understanding true characteristics and establishing novel treatment strategy of this disease.