Answer:
Most breast lumps are benign cysts, particularly in younger women. Size and tenderness may vary with the menstrual cycle. When lumps are tender, they are more likely benign, but about 10 percent of breast cancers do cause breast pain or tenderness.
Cancers
tend to feel much harder than benign cysts and fibroadenomas. Both benign and malignant
masses can be rounded and mobile. Only when cancers are quite advanced are they fixed
to skin or the underlying chest wall, and not moveable.
Any new, persistent,
or changing lump in your breast should be evaluated by your physician. Sometimes mammograms
and ultrasound can differentiate between benign and malignant breast masses. But,
often just a needle aspiration of the lump can quickly prove that it is just a cyst
when fluid drains.
The best approach is to get regular screening mammograms
on a schedule defined by the American Cancer Society - starting early if there
is a family history of breast cancer or other risk factors. With very dense breasts
that are difficult to evaluate with exam and mammogram, targeted or 3D ultrasound
may be added.