Extracardiac tumor tracer uptake in myocardial perfusion scintigraphy.

A 74-year-old man was referred to the Cardiology clinic with a 3-week history of exertional chest tightness. These episodes lasted a few seconds without any limitation to activity. The gentleman is an ex-smoker and a hypertensive on treatment. The results of the clinical examination and ECG were unremarkable. An exercise tolerance test was found to be negative, albeit at a subtarget heart rate. Myocardial perfusion scintigraphy with technetium-99 m–labeled tetrofosmin was subsequently performed, and the result was negative for inducible ischemia. However, there was an incidental finding of focal extracardiac tracer uptake seen on the source images. This was identified, on the computed tomography scan performed for attenuation correction, as uptake within a 5 × 3 cm mass present in a destroyed anterior right fourth rib (Figures 1 and 2, Movie I in the onlineonly Data Supplement). A contrast computed tomography scan confirmed this as a solitary lesion. He was found to have a moderate-sized IgGK paraprotein with a trace of urinary Bence-Jones protein. Bone marrow aspirate showed 2% plasma cells consistent with monoclonal gammopathy of unknown significance. Computed tomography–guided biopsy of the lesion confirmed a malignant plasmacytoma. The gentleman has been referred for local radiotherapy by the hematologists. It is known that myocardial perfusion scintigraphy agents such as tetrofosmin are taken up in a variety of tumors. Although the incidence of pathological extracardiac uptake is rare, review of the raw data must be performed routinely by physicians before interpretation to avoid missing potentially fatal conditions. Our case confirms the importance of the review of these areas in myocardial perfusion scintigraphy studies.