Benign myofibroblastic lesion of the breast, actually more common in men
Mean age 64yrs
Classically, there are bundles of cytologically bland spindle cells separated by thick, hyalinized bands of collagen
Usually well demarcated from surrounding breast by a psuedocapsule; the lesion itself is devoid of lobules or ducts
In this particular variant, the cells are embedded in a fibrous, collagenous stroma without the deeply eosinophilic collagen bands that are classically seen
Cells are usually positive for CD34, muscle markers (actin, desmin, calponin), but are negative for p63 and S-100
Mesenchymal : Myofibroblastoma