BACKGROUND: Breasts are assumed to be symmetrical bilaterally, and abnormal findings on breast imaging are largely based on such an assumption. Clinically noticeable breast asymmetry beyond that of normal range is rarely encountered.

CASE REPORT: A 38-year-old female presented with unilateral enlargement of her left breast for 3 months and complained of polymenorrhea twice a month. Mammography and ultrasonography revealed that the left breast had a larger volume of fibroglandular tissue than the right breast, without accompanying signs of malignancy or abnormality. Magnetic resonance imaging demonstrated unilateral, diffuse, stippled enhancement in the left breast, which was located peripherally in the early phase and propagated centrally in the delayed phase with a persistent kinetic pattern. Ultrasonography-guided core needle biopsy was performed for the left breast, leading to a pathological diagnosis of fibrocystic change. The condition could be presumably due to a different response of the breasts to imbalance in endogenous hormones.

CONCLUSIONS: Based on our findings, we believe that radiologists should consider that the breast has a unique dynamic physiology and that features on breast imaging can be affected by hormonal alteration.

Keywords: Breast, Fibrocystic Breast Disease, Magnetic Resonance Imaging, Mammography, Ultrasonography