The germinal cell layer surrounding the oocyte before ovulation is known as :

In one area , the granulosa cells are collected together to form a projection into the cavity of graffian follicle. This projection is referred to as the discus proligerus or cumulus oophorus. The ovum itself lies within it.With the exception of area around the discus, the peripheral granulosa cells form a layer only a few cells in thickness.,whereas at the discus the cells are between 12 and 20 layers thick. Reference: Shaw's Textbook of Obstetrics 15th edition page 28