CA125 measured during menstruation can be misleading.

The aim of these case reports and literature review is to report the importance of cyclical variation of serum CA-125 levels in two patients with endometriosis. Two case reports and a literature review of cyclical variation in serum CA-125 levels are discussed. There was significant variation in serum CA-125 levels taken during menses and mid-cycle in these two cases. Serum CA-125 levels increase dramatically during menstruation in women with endometriosis. This is important when assessing disease status.