Hello, I have a 9cm cyst on my left ovary. It is not the corpus luteum, that one was found on my right ovary and much smaller. The giant cyst has been there for a long time. Mine is being monitored and will be reassessed at my 12 week scan. If it has grown, they may want to do a small procedure to shrink it. The biggest concern with a large cyst is torsion. I really hope it has shrunk, however, I can feel it at times. I bet yours is just the corpus luteum being so small.