Mammograms are an important tool in the early detection of breast cancer. These X-ray images help identify abnormalities, often before a lump can be felt. Early detection through regular screening can significantly improve treatment outcomes. While beneficial, it is important to understand a common aspect of breast cancer screening: the false positive result.
Understanding Mammogram False Positives
A mammogram false positive occurs when a screening mammogram indicates a potential abnormality that, upon further investigation, is determined not to be cancer. A true positive, in contrast, correctly identifies cancer, while a false negative means cancer is present but the mammogram appears normal.
False positives are a common occurrence in breast cancer screening. For women aged 40-49, false positives occur in about 10-12% of mammograms. Over a decade of annual screenings, approximately 50-60% of women can expect to experience at least one false positive result. This highlights that receiving a call for additional imaging is a frequent part of the screening process and does not automatically mean cancer.
Common Reasons for False Positives
Several factors can contribute to a mammogram yielding a false positive result. One reason is dense breast tissue, which contains more fibrous and glandular tissue than fatty tissue. This density can obscure or mimic abnormalities on a mammogram, making it challenging for radiologists to distinguish between normal tissue and potential cancerous lesions. Younger women often have dense breast tissue, contributing to higher false positive rates.
Benign breast conditions also frequently lead to false positives. These include cysts, which are fluid-filled sacs, and fibroadenomas, which are non-cancerous solid lumps. Small calcium deposits, known as calcifications, can also appear on mammograms and sometimes be mistaken for cancer, especially if they are clustered or have suspicious patterns. Normal variations in breast tissue, hormonal changes, previous breast surgeries or biopsies, and overlapping breast tissue can also create shadows or areas that look like masses, leading to a false positive.
Navigating a False Positive Result
Receiving a call back after a mammogram can cause anxiety, but most abnormal findings are benign or normal breast tissue. When a false positive occurs, the next steps typically involve additional imaging tests for a clearer picture.
These follow-up procedures often include a diagnostic mammogram, which takes more detailed images. An ultrasound may also be performed. In some cases, a breast MRI might be recommended. If these additional imaging tests still show a suspicious area, a biopsy may be necessary. This procedure involves removing a small tissue sample to determine if cancer cells are present. Approximately 80% of breast biopsies performed due to suspicious mammogram findings are found to be benign. Continuing with these follow-up tests is important for confirming the absence of cancer or for early diagnosis if cancer is present.