small increases in the size of the ovary at times could be due to hormonal
influences in your body, causing functional cysts, which are usually of small sizes. A large cyst as what you are describing from ultrasound
results need a more keener investigation, to actually elucidate whether its organic or inorganic. Delayed diagnosis could lead to complications such as torsion, hemorrage or rupture, which at times could be very painful or necessitate surgery. A proper consultation with your gynecologist for mproper investigations to rule out malignancy and actually confirm or control the size of the cyst, together with other lab results are imperative.