If an abnormal mammogram turns up, a breast biopsy is the preferred follow-up procedure even though other options are available. Biopsy has long been considered the “gold standard” in the diagnosis of breast cancer.
Even a biopsy may not be 100 percent accurate. Research has shown that the false-negative rate for core biopsy, a type of needle biopsy, can be as high as 8 percent. Needle biopsies, in particular, are relatively inaccurate compared to surgical biopsies. A core needle biopsy, for example, may miss a cancerous tumour and take a sample of normal tissue instead.
In the case of fine-needle aspiration, the evaluation may potentially be inaccurate because the tissue sample taken is very small. When used alone, up to about 10% of breast cancers may be missed. Consequently, when a fine needle aspiration does not find cancer, it may still need to be followed up with another type of biopsies, such as a core needle or surgical biopsy.