Non-mass enhancements (NMEs) on breast Magnetic Resonance Imaging (MRI) are areas of unusual signal intensity that do not form a distinct lump or mass. While the detection of an NME can be concerning, it does not automatically signify the presence of cancer. These findings are often evaluated further to determine their nature. This article aims to provide clear information about NMEs, how they are evaluated, and the likelihood of them being cancerous.
Understanding Non-Mass Enhancements
NMEs appear on breast MRI when contrast material, such as gadolinium, collects in a diffuse, non-lump-like pattern within the breast tissue. Unlike a well-defined mass with distinct borders, NMEs show enhancement that is spread out, often intermingled with normal breast tissue. Radiologists describe these patterns based on their distribution and appearance.
Common patterns include focal (a confined area), linear (straight or branching, suggesting duct involvement). Segmental NMEs appear in a triangular or cone shape pointing towards the nipple, often indicating a single duct system. Regional NMEs span a broader area, while diffuse patterns are widely scattered. Various factors, including blood vessel changes, inflammation, or abnormal tissue growth, can cause the contrast agent to accumulate.
Diagnosing and Classifying NMEs
Upon initial detection, NMEs are investigated using specific MRI features. Dynamic contrast-enhanced MRI (DCE-MRI) assesses how quickly contrast enters and leaves (kinetics) and its shape and spread (morphology). These characteristics help radiologists classify NMEs using the Breast Imaging Reporting and Data System (BI-RADS).
BI-RADS assigns a category to the NME, indicating its level of suspicion. A BI-RADS 3 category suggests a “probably benign” finding (less than 2% likelihood of malignancy), typically managed with short-term follow-up. In contrast, BI-RADS 4 signifies a “suspicious abnormality” with a higher probability of cancer, prompting a recommendation for biopsy. For concerning NMEs, an MRI-guided core needle biopsy may be recommended to obtain tissue samples. This procedure uses MRI to guide a needle to the NME’s exact location.
The Likelihood of Cancer in NMEs
The percentage of non-mass enhancements found to be malignant varies, but studies indicate a significant minority are cancerous. Malignancy rates for NMEs can range from 12.2% for BI-RADS 4 focal NMEs to higher percentages based on specific characteristics. The likelihood of cancer in an NME is strongly influenced by its imaging characteristics, including its morphology and kinetic behavior.
Certain features are associated with a higher probability of malignancy. Segmental or linear NMEs are more suspicious than focal or regional patterns. Heterogeneous or clumped internal enhancement patterns also raise suspicion, with clustered ring enhancement being particularly concerning.
Kinetic analysis, describing how contrast moves in and out of the NME, also provides clues. Rapid uptake and quick washout are often associated with malignancy. Conversely, persistent enhancement patterns (where contrast remains over time) are more often benign.
Management and Follow-Up
The management of a non-mass enhancement depends on its BI-RADS classification and biopsy results. For BI-RADS 3 NMEs (probably benign), short-interval follow-up imaging, typically repeat MRI in 6-12 months, ensures stability. If the NME remains stable over a period, it may be downgraded to a benign finding.
When an NME is BI-RADS 4 or 5, indicating higher suspicion for malignancy, biopsy is recommended. If the biopsy confirms cancer, surgical removal of the affected tissue is often the next step. Even if biopsy results are benign but imaging remains suspicious, discuss the best course of action with a healthcare provider. This might still involve surgical excision to confirm the diagnosis. Personalized care, considering the specific NME characteristics and the individual’s overall health, guides these decisions.