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
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 .