Large Ovarian Follicle Cyst: Benign Mimic of Cystic Adult Granulosa Cell Tumor.

While most ovarian follicle cysts are <8 cm in greatest dimension, much larger follicle cysts (up to 18.5 cm) have been reported. To our knowledge, the FOXL2 mutation status of such cases has not been documented in the literature. Here, we report the features of a 14 cm ovarian cyst with no FOXL2 mutation detected by targeted next-generation sequencing. While adult granulosa cell tumor was the chief entity in our differential diagnosis, the absence of convincing nuclear grooves, lack of architectural variability, presence of a theca layer, and absence of FOXL2 mutation were consistent with a diagnosis of ovarian follicle cyst.