ACP5 and AL amyloidosis: Histologic and electron microscopy studies from these authors showed that B cell malignancies presenting bone alterations, including CLL, displayed a discrete number of osteoclasts, identified as tartrate-resistant acid phosphatase (TRAP)+ cells and close to bone trabeculae, but smaller than those detected in multiple myeloma (MM): these cells induced areas of micro-resorption and appeared very close to malignant lymphoid cells.