I'm 45 with painful periods 4 well over a yr. Diagnosed with lge than usual cyst lft ovary? Wud the cyst be there over a yr too? .Cud it b cancerous?

Left ovarian cyst. Possible, however, nobody knows for sure how long the cyst has been there unless you had something a year ago to compare with. You should have it evaluated by agynecologist and have serial sonogram to follow up. If the cyst looks suspicious from the size, pattern etc- then your doctor has to investigate further to rule out malignancy.