Corpus Luteum with Cavity.

Corpus Luteum with Cavity.
Corpus luteum with a cavity (lacuna) sometimes referred to as a hollow corpus luteum, or misleadingly as a "cystic CL". These corpora lutea are functionally normal. They produce a comparable amount of progesterone to that of a normal diestrous CL or a gravid CL.

Bartolome J (2006)