To describe the radiologic findings of granulomatous mastitis of the breast.

This study included 19 patients (age range: 22 to 56 years; mean 37 years) with 22 lesions that were pathologically confirmed as having granulomatous mastitis. All the patients underwent a breast ultrasonography and 13 patients underwent a mammography.

The results of the mammography revealed focal asymmetry (n=9), multiple ill-defined isodense nodules (n=2), ill-defined nodular density on a craniocaudal view (n=1), and unremarkable finding (n=1). The sonographic findings included continuous or discontinuous multiple tubular and nodular low echoic lesions (n=7), ill-defined heterogeneously low echoic lesion (n=5), irregular-shaped, ill-defined low echoic mass (n=4), fluid collection with internal floating materials suggesting the presence of an abscess (n=4), ill-defined heterogeneously low echoic lesion and abscess (n=1), and multiple ill-defined nodules (n=1).

In the case of granulomatous mastitis, the mammography results indicate a lack of specificity between normal findings and focal asymmetry. The sonographic findings indicate that ill-defined heterogeneously low echoic lesions or irregularly shaped, ill-defined low echoic masses are difficult to differentiate from breast cancer. The sonographic findings of abscesses indicate a difficulty in differentiating them from cases of pyogenic mastitis. However, multiple tubular and nodular low echoic lesions, especially with a continuous appearance, should point to granulomatous mastitis, and is helpful in its differential diagnosis and treatment.