FOXL2 and in situ carcinoma: GB arises in the context of granulosa cells, staining positive for FOXL2 and negative for SOX9 (a Sertoli cell marker), this in contrast to the precursor lesion arising in a testicular environment, being CIS, in which the supportive (Sertoli) cells are negative for FOXL2 and stain positive for SOX9 [22].