How can you distinguish between benign and malignant breast tumors?

After bx: On examination a true lesion in a women past 40 yrs of age ,when fibroadenomas don't present denovo, will feel like a firm lump when pt. examined with hand behind side being examined. This in distinction to fibrocytic changes that are soft and diffuse. On mammo the lesion appears as a stellate mass, May be associated with skin dimpling. Bx definitive for diagnosis.