Cystic Corpus Luteum.

Cystic Corpus Luteum.
The right ovary shows a bulging, round corpus luteum that may be mistaken for a luteal cyst on palpation because of its shape. However, there is an ovulation papilla. The term cystic CL is perhaps unfortunate because these cavitated CL produce the same concentration of progesterone as a solid CL, hence they function normally.

Drost M (1970)