What are the symptoms of a breast cyst? i'm a 21 year old female.

No symptoms: Many breast cysts cause no symptoms. Some can cause pain. You should have it checked by a doctor if you haven't already, to make sure it is a cyst.

(painful) lump: Breast cysts arise from fluid accumulation within a blocked milk duct. These appear to be estrogen-dependent and very common, occurring in 35-50% of women aged 35-50. When small, they usually are "silent"; but, when large, they can be quite painful. Aspiration is reserved for those that are causing pain or those that are atypical in appearance by ultrasound.