How do i differentiate between breast cancer and fibrocystic disease?

YOU can't: Only an experienced doc with appropriate imaging (mammography, ultrasound, MRI - as indicated) can define a breast lump. Many times were not even sure and a biopsy is needed to sort it out. Any lump persisting through a menstrual period needs to be checked out!

Exam,Mamm,(sono)Gram: Fibrocystic changes may interfere w/breast examination and/or mammography. Nevertheless, using these modalities along w/breast ultrasound, we can usually distinguish between the two. Rarely, we need to check an MRI or even do a breast biopsy to evaluate a suspicious lump or mammographic abnormality.