Background: There are number of entities that can result in diffuse unilateral findings on breast MRI. This can create a diagnostic challenge. Therefore, it is important for breast radiologists to be aware of the differential diagnosis of diffuse unilateral breast MRI entities when this pattern is observed.
Learning Objectives: 1. Discuss imaging findings of diffuse unilateral breast entities encountered on mammography and their corresponding imaging findings on breast magnetic resonance imaging (MRI). 2. Compare and contrast etiologies of diffuse unilateral breast abnormalities seen on mammogram and MRI.
Abstract Content/Results: This educational review will provide a pictorial review of seven entities which can cause diffuse unilateral findings on breast MRI. We will discuss imaging characteristics and MRI findings of these entities which include diffuse breast cancer, diffuse inflammatory breast cancer, unilateral diffuse granulomatous mastitis, lupus mastitis, unilateral venous obstruction, unilateral lactation, and unilateral radiation-induced changes. Multiple examples will be shown.
Conclusion: Diffuse breast cancer typically demonstrates diffuse enhancement on magnetic resonance imaging often with confluent masses and non-mass enhancement encompassing several quadrants. Inflammatory breast cancer presents with non-mass enhancement and is characterized by unilateral skin and trabecular thickening and edema. Granulomatous mastitis presents with heterogenous ill-defined masses, non-mass enhancement with mixed kinetics, cystic lesions with rim enhancement, and focal skin thickening. Lupus mastitis mimics the stages of fat necrosis with multiple lesions of fat cavities and a post-contrast rim enhancement. Venous obstruction presents with unilateral skin thickening and increased vascularity with dilated mammary ducts. Radiation-induced changes of the breast leads to two distinct patterns: early manifestations of whole breast radiation include interstitial edema and skin thickening in the radiated breast while and later manifestations include reduced background parenchymal enhancement to the treated breast. Unilateral lactation demonstrates diffuse increased breast parenchymal enhancement and increased fibroglandular tissue of the lactating breast. This educational review will discuss relevant literature and pertinent imaging so that proper differential diagnoses of diffuse unilateral breast abnormalities on MRI can be developed.
