We’ve all had an X-ray - on a bone, or a joint, or checking for a cavity in the dentist’s office. Did you know that one of the most common uses of X-rays is for mammograms? A mammogram is the very best way to detect breast cancer early, when treatment is most effective. When should a woman get her first mammogram, and how are they interpreted?

(By the way, the term X-ray is short for X-radiation, discovered in 1895. The “X” was used because at the time, it was an unknown type of radiation.)

Guidelines for when a woman (at average risk for breast cancer) should have mammograms change. Current recommendations are back to having an annual mammogram starting at age 40; note that one in six new breast cancers are found among women between the ages 40 and 50. Those at higher risk should start earlier. There is limited scientific data on whether mammograms actually save lives after the age of 74, so practices differ. Age is not the sole criteria for when to stop having this diagnostic test; I discuss with each of my older patients how likely they would be to intervene if something were to be found on their mammogram.

Mammograms now also include an assessment of breast density, which is a description of how much of the breast tissue is fibrous and glandular, as compared to fatty. Dense breasts are not unusual, but the denser the breast tissue is, the harder it can be to detect abnormal areas. When a mammogram shows dense breasts, more testing may be recommended, including the use of a 3D mammogram. Also, glandular tissue (more prominent in dense breasts) is more susceptible to cancer than is fatty tissue. So, in addition to making the mammogram more difficult to read, women with dense breasts do have a higher risk of breast cancer than do women with fatty breasts.

Mammograms also detect calcifications, which are tiny flecks of calcium in the breast tissue. They usually cannot be felt, but do show up on a mammogram. They are very common, and the huge majority of them are noncancerous. Their size, shape and distribution may indicate whether they are benign, or need to be biopsied. Cysts and fibroadenomas will also show up in a mammogram, but are rarely cancerous.

A radiologist reads the mammogram and assigns a BI-RADS result. (This is the same system used for breast ultrasounds.) Results range from BI-RADS zero through six. BI-RADS 0 indicates that additional films are needed. BI-RADS 1 and 2 are normal readings. BI-RADS 3 is considered probably normal, but may require more frequent follow-up. BI-RADS 4 is a suspicious finding. BI-RADS 5 is highly likely to be malignant and a biopsy or other surgery is recommended. BI-RADS 6 confirms or follows up on a previously confirmed cancer.

If you are over 40 and female, I urge you to get annual mammograms. They are a great tool for early cancer detection.