Non-mass lesions (NML) represent approximately 5% of lesions seen on screening or diagnostic breast ultrasound examinations. Also called focal shadowing, duct-like structures, ductal changes, or non-mass image-forming lesions, NMLs have a broad pathologic spectrum. This spectrum ranges from benign (fibrocystic changes or stromal fibrosis) to ductal carcinoma in situ (DCIS) to invasive cancer.
Knowledge of and understanding about NMLs is scarce, according to Korean breast imaging specialists from the CHA Bundang Medical Center of CHA University in Gyunggi-do. They investigated 119 women who had NMLs to determine their final outcomes, and to identify radiologic variables that differentiate malignant from benign lesions.
The study, described in an article in Acta Radiologica, analyzed 119 consecutive patients (21 to 69 years old) with 121 NMLs identified by breast ultrasound examination over a four year period. Mammographic tissue density was collected and categorized from the 95 women old enough to have had screening mammograms.
The authors defined NMLs as lesions visible on two orthogonal planes, but which could not be characterized as a distinct mass because of lack of a conspicuous margin or shape. Because ultrasound feature description of NMLs has not been standardized, the authors had created categories for distribution and associated features. NMLs were classified as focal, linear-segmental or with a regional pattern for distribution. Features of NMLs were categorized by calcification, architectural distortion, or abnormal ductal changes. Each sub-category had specific pre-defined characteristics and parameters.
A total of 33 malignancies in 33 patients were pathologically confirmed. The majority of malignancies (51.5%) were diagnosed as DCIS and followed by invasive ductal cancer (24.2%). 82 benign diseases were identified in 81 patients, with the majority being fibrocystic changes (28%), stromal fibrosis (25.6%), and fibroadenomatoid hyperplasia (14.6%).
Lead author Jong Won Park, MD, and co-authors reported that 60% of the patients with malignancies had palpability symptoms — the only symptom they reported — compared to 22% of patients with benign lesions who reported symptoms. (Of the women with benign lesions, only 9% reported palpability.) Age and mammographic density were not significantly different between patients with malignant and benign lesions. Calcification combined with asymmetry seen on mammograms was more frequent in malignant (37.5%) than in benign lesions (6.3%).
The breast ultrasound examinations did show significant differences in the distribution between malignant lesions and benign. Linear or segmental distributions were identified in 45.5% of malignant lesions compared to 17% of benign ones. Focal distribution was identified in 60.2% of benign lesions compared to 33.3% of malignant ones. Calcification (27.3% vs 10.2%) and architectural distortion (18.2% vs 4.5%) were also significantly more prevalent in malignant lesions than benign ones.
“Breast NMLs on ultrasound showed high risk of malignancy…NMLs have to be managed according to clinical, mammographic, and Ultrasound findings,” they concluded. They stated that additional research is needed, preferably performed by multiple institutions with larger study groups.
Predictors of malignancy of non-mass breast lesions on ultrasound. Appl Radiol.