In humans, Mb is synthesised at concentrations of ∼200–300 μM in striated muscle and, although at much lower levels, in a variety of human tumours including medullomyoblastoma (Smith and Davidson, 1984), thymolipoma (Iseki et al, 1990), acute leukaemia (Ruck et al, 1995) and desmoplastic small round cell tumours (Zhang et al, 2003). Here, MB is linked to neoplasm.