Clinical meaning
Ovarian cysts are fluid-filled sacs arising from or within the ovary. The vast majority are benign and classified as functional (physiologic) or neoplastic. Functional cysts arise from normal ovarian folliculogenesis. During each menstrual cycle, FSH stimulates recruitment of a cohort of primordial follicles. The dominant follicle reaches 18-25 mm under FSH/LH stimulation, producing increasing estradiol through granulosa cell aromatase (CYP19A1) activity converting thecal androgens to estrogens. The LH surge triggers ovulation - rupture of the follicle wall via MMP activation, prostaglandin-mediated inflammation, and proteolytic degradation of the follicular surface. A follicular cyst forms when the dominant follicle fails to ovulate or fails to regress - continued FSH/estradiol stimulation causes progressive fluid accumulation, typically reaching 3-8 cm. Most resolve within 1-3 menstrual cycles. Corpus luteum cysts form when the postovulatory corpus luteum fails to regress normally. After ovulation, granulosa cells undergo luteinization (stimulated by LH), transforming into large lutein cells that produce progesterone via cholesterol side-chain cleavage enzyme (CYP11A1) and 3β-HSD. The corpus luteum is highly vascular - angiogenesis driven by VEGF creates a rich capillary network. Corpus luteum cysts may...