Regarding breast cancer; mammograms screen for breast cancer, but any physician (family care, internal or general practitioner) can give you a referral to get one. Mammograms are recommended at or over the age of 40 on a yearly basis unless of you have certain risk factors in your medical of family history that change the recommendation to start mammograms at an earlier age (usually 35).
Treating cancer requires further physician specialization. Breast Cancers are treated by Oncologists while gynecologic cancers are treated by Gynecologic Oncologists. I would recommend establishing care with an OBGYN to discuss each of your questions in further detail.
Dr. von Walstrom