Fig. 1.

Inflammatory pseudotumor of breast in 60-year-old woman.

A, B. Left craniocaudal (A) and mediolateral oblique (B) mammograms reveal 1.5-cm-sized ill-defined, high-density mass (arrows) in axillary tail area of left breast.

C. Transverse US scan reveals irregular shaped, ill-defined homogeneous hypoechoic mass with echogenic halo in left axillary tail region. We found nodule surrounded by fat lobules and mass appearing to infiltrate around fat lobules.

D. Color Doppler study reveals moderate vascularity in peripheral halo portion of mass.

E. Upon gross pathology, we observed ill-defined pinkish-white mass (arrowheads) without necrosis or hemorrhage.

F. For microscopic findings at high magnification, proliferating spindle cells had bland-looking nuclei and nucleoli were inconspicuous. There were occasional mitoses (up to 3 of 10 per high-power field), but atypical mitoses were not found (Hematoxylin & Eosin staining, ×200).

G. Following immunohistochemical assay, spindle cells were found to be reactive for anti-SMA (smooth muscle actin), which demonstrates myofibroblastic differentiation (×200).