Myoglobin (MB) is an iron- and oxygen-binding haemoprotein of the globin superfamily that contributes to intracellular oxygen storage and transcellular facilitated diffusion of oxygen. Damaged muscle releases large amounts of myoglobin, and it is a useful and sensitive biomarker for muscle injury and heart attacks. It also shows positivity in rhabdomyosarcoma and tumors with skeletal muscle differentiation. In immunohistochemistry of normal tissue, myoglobin antibodies are positive in striated cardiac and skeletal muscle. References: Clin Bio. 2005. 38 (11): 1027–30, PMID: 16125162; The Journal of Experimental Biology. 2004. 207 (Pt 20): 3441–6, PMID: 15339940;