How often are microcalcifications cancer?

It depends on where: Microcalcifications, can be benign or indicative of possible malignancy, often in- situ cancers as is the case with breast cancer. They can also occur in thyroid gland where they are often associated with cancer.

? in a mammogram ?: About 12% of microcalcifications seen on mammography are indicative of cancer. There are characteristics of the ca which lead the mammographer and/or surgeon to be suspicious. Good luck.