Most malignant (non-adipose) mesenchymal soft tissue neoplasms (Table 1) did not stain for UCP1, but it was noted that tumour cells in a few leiomyosarcomas and alveolar and pleomorphic rhabdomyosarcomas stained strongly for UCP1 when the polyclonal antibody was diluted 1:500 or less (Fig. 4a–c). Here, UCP1 is linked to pleomorphic rhabdomyosarcoma.