Engraftment of pMM cells in humanized mice coincides with osteolysis. (A) H&E staining shows an irregular bone surface with osteoclast-like cells (arrows). Shown is a representative slide (middle panel) of an MM-infiltrated ossicle (s) covered with bone (b). The left and right panels show the boxed areas at higher magnification. (B) Analysis of control (left panel)–, pAML (middle panel)–, and pMM (right panel)–engrafted ossicles for the presence of osteoclasts by tartrate-resistant acidic phosphatase staining. Shown are representative slides of a control, pMM-, and pAML-engrafted ossicle stained for tartrate-resistant acidic phosphatase.