Thallium 201 chloride uptake in tumours, a possible complication in heart scintigraphy

An abnormal uptake pattern of 201Tl thallous chloride observed during myocardial scintigraphy of a patient with known thoracic tumour localization suggested the possibility that thallous chloride may also accumulate in tumours. This was confirmed by observing 201thallous chloride accumulation in rhabdomyosarcoma implants in rats. Thallium 201 accumulation in tumour cells should be borne in mind as a possible complicating factor when using this reagent for the evaluation of cardiac conditions in oncological patients.