[en] Full text: A 61-year-old female presented to the Nuclear Medicine Department with shortness of breath and central chest pain for the previous 2 months, for investigation of reversible myocardial ischaemia. The patient was administered 259 MBq of ⁹⁹Tc^m-sestamibi (MIBI) at rest, and SPET images of myocardial perfusion were acquired using a Siemens Multispect3 gamma camera, at 45 min post-administration. The patient then underwent 3 min of exercise on a bicycle, achieving a peak workload of 25 W and a peak heart rate of 161 beats-min^-1 The exercise was terminated due to the patient's usual shortness of breath. The ECG was normal at rest and peak stress. The patient was injected with 777 MBq of ⁹⁹Tc^m-MIBI 2 min prior to peak exercise. SPET images were again acquired at 45 min post-administration. Gated images could not be performed. Reconstructed images showed no scintigraphic evidence of reversible myocardial ischaemia, but there was a fixed anterior wall defect. Review of the raw planar images demonstrated markedly increased lung uptake in a heterogeneous distribution. Further questioning confirmed a history of follicular thyroid cancer with pulmonary metastases, which were confirmed on current chest X-ray, in a distribution identical to the scintigraphic images. The fixed anterior defect may be a reconstruction artefact, rather than a prior infarct. In conclusion, we have demonstrated an unusual cause for increased lung uptake on routine myocardial perfusion imaging with ⁹⁹Tc^m-MIBI; thyroid cancer should be included in the differential diagnosis of such an appearance