ACP5 and thyroid gland carcinoma: As a first step, we validated the tartrate-resistant acid phosphatase 5b (TRACP5b) as a specific and sensitive marker of OC activity (Halleen et al., 2000, 2001; Avnet et al., 2008; Savarino et al., 2010) in a continuous series (n = 29) of patients with osteolytic BM from breast, renal, and thyroid carcinoma (Table 3).