A mammogram is a key tool for monitoring breast health and detecting potential abnormalities. Radiologists use a standardized system to classify findings, ensuring clear communication among healthcare providers. This article focuses on what a BI-RADS Category 4 result signifies.
The BI-RADS Classification System
The Breast Imaging Reporting and Data System (BI-RADS) is a universal scoring system developed by the American College of Radiology. It standardizes how radiologists describe mammogram, ultrasound, and MRI findings, ensuring consistency in reports and follow-up recommendations. BI-RADS categories range from 0 to 6, each representing a different level of concern and guiding patient care.
Category 0 indicates an incomplete assessment, meaning additional imaging is needed. Categories 1 and 2 signify negative findings, where breast tissue appears normal or abnormalities are definitively benign. Category 3 suggests a finding is probably benign, with a very low chance of being cancerous (typically less than 2 percent). Categories 5 and 6 indicate a high probability of malignancy or biopsy-proven cancer, respectively. This spectrum helps place Category 4 within the broader context of breast imaging results.
Understanding BI-RADS Category 4
A BI-RADS Category 4 classification indicates a “suspicious abnormality” on breast imaging. This finding is not clearly benign nor definitively malignant, requiring further investigation. Radiologists assign this category when there is concern the abnormality could be cancerous, though it is not a certainty. Category 4 is a broad classification, encompassing a range of suspicion levels.
This category is divided into three subcategories for more specific guidance. Category 4A represents a low suspicion for malignancy (2% to 10% probability of cancer). Category 4B indicates a moderate suspicion (10% to 50% chance of malignancy). Category 4C denotes a high suspicion (50% to 95% probability). Examples include new masses with irregular shapes or margins, or clusters of calcifications with suspicious patterns.
Despite the term “suspicious,” most BI-RADS 4 findings are benign after a biopsy. The overall malignancy rate for BI-RADS 4 lesions typically ranges from 20% to 35%. This means 65% to 80% of these findings are not cancerous. While a BI-RADS 4 result warrants follow-up, it does not automatically mean a cancer diagnosis.
Next Steps After a BI-RADS 4 Finding
Upon receiving a BI-RADS 4 result, a biopsy is typically recommended. This procedure obtains a tissue sample from the suspicious area for microscopic examination by a pathologist. A biopsy is the only definitive way to determine whether the abnormality is benign or malignant.
Several types of biopsies are available, chosen based on the abnormality’s size, location, and characteristics. A fine-needle aspiration (FNA) biopsy uses a thin needle to withdraw fluid and cells. A core needle biopsy uses a slightly larger needle to remove small, tube-shaped tissue pieces for analysis. These procedures are often guided by imaging techniques like ultrasound, mammography (stereotactic biopsy), or MRI to ensure precise targeting. In some cases, a surgical (excisional) biopsy may be recommended, involving removal of the entire abnormal area and a margin of surrounding healthy tissue.
What Biopsy Results Reveal
After a biopsy, the tissue sample is sent to a pathology laboratory for detailed examination. The pathologist’s report definitively classifies the cells. If results are benign, no cancerous cells were found. In such cases, further immediate action may not be necessary, though regular follow-up imaging might be recommended to monitor the area.
If the biopsy reveals malignant cells, it confirms the presence of cancer. A treatment plan will then be developed based on the cancer’s specific type and characteristics. The biopsy process clarifies the diagnosis and guides appropriate medical management, whether continued monitoring or cancer treatment.