PMC5879850_01
(a) Mammogram showing well-defined soft-tissue density in retroareolar region (arrow) of the right breast. (b) Scanner view showing a well-circumscribed tumor, (H and E, x40). (c) Low-power view showing a tumor composed of fascicles of benign spindle cells, (H and E, x100). (d) High-power showing tumor cells interspersed with ropy collagen (H and E x400)
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F1
The mammogram identified a well-defined soft-tissue density in the retroareolar region without any evidence of microcalcification and classified as Breast Imaging Reporting and Data System 4a [Figure 1a]. On paraffin sections, the tumor was composed of spindle cells in fascicles traversed by thick ropy collagen fibers at places [Figure 1b-d]. Mitotic figures were occasional <1/50 high-power field and the tumor showed many thick-walled blood vessels.
(a) Tumor cells showing CD34 positivity (IHC x100). (b) Tumor cells showing smooth muscle actin positivity (IHC x100)
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F2
IHC, the tumor cells expressed CD34 [Figure 2a], vimentin, and smooth muscle actin (SMA) [Figure 2b] and were negative for S100. In view of the immunoprofile and the histology, a final diagnosis of MFB was given.