Polyclonal antibodies can cross-react with structurally-related molecules [28] so it is possible that staining with the anti-UCP1 antibody of malignant tumour cells in some non-adipose sarcomas could represent a cross-reaction with a UCP1 homologue, such as UCP2 and/or UCP3 in rhabdomyosarcomas. The gene discussed is UCP2; the disease is rhabdomyosarcoma.