Ovarian cyst vs follicle

Lots of patients are unsure about the difference between an ovarian cyst and a follicle.

The reality is that as far as an ultrasound scan is concerned, they both look exactly the same - they both appear like black bubbles.

The only differentiation is based on their size, which means  if it's large, we call it a cyst, and if it's small, we call it a follicle.

Now, the arbitrary size cutoff is 20- 25 mm, which means many patients think that a follicle should be 25 millimeters or less. The reality , however, is that there is a lot of overlap, and large follicles look exactly like small cysts do.

On a single scan, it's impossible to differentiate between the two, which is why serial ultrasound scans are so helpful . Follicles usually grow at 1-2 mm per day, and while cysts can grow as well, they are usually remain the same size over a few days

However, the final proof of the pudding is in the eating. When we do IVF and stick a needle in the follicle,  and get an egg, we call it a follicle. If we don't get an egg, we call it a cyst ! But we'll only know at the time of the egg collection whether this was a cyst or a follicle .

Read more at https://www.drmalpani.com/knowledge-center/articles/the-difference-between-follicles-and-ovarian-cysts