Polycystic ovary morphology (PCOM)
The ultrasound appearance of many small follicles in the ovary. One of the three Rotterdam criteria, and the source of the old, inaccurate "polycystic" name.
Polycystic ovary morphology is the appearance, on an ultrasound, of a higher-than-usual number of small follicles in the ovary, sometimes arranged in a "string of pearls" pattern around the edge.
It is one of the three Rotterdam criteria for PMOS. Importantly, what the scan shows are antral follicles, not cysts. This is the origin of the misleading "polycystic" name that the 2026 rename moved away from.
PCOM on its own does not mean someone has PMOS. Many people have this ovarian appearance without the condition, especially when young, so it counts only alongside the other criteria. For adolescents, the ultrasound criterion is not used at all, because a higher follicle count is common and normal in those years. A clinician reads PCOM in context, never in isolation.