Malignant transformation of bronchogenic cyst revealed by 99mTc-MIBI-SPECT.

Adenocarcinoma arising from a mediastinal cyst was detected by exercise technetium-99m hexakis-2-methoxyisobuty-lisonitrile (99m)Tc-MIBI scintigraphy in a 65-year-old woman with known coronary disease. This guided further investigations and resection of the tumor which stained positive for P-glycoprotein. Three years earlier, myocardial scintigraphy was negative, probably due to down-expression of P-glycoprotein because the cells were in the early stages of carcinogenesis. After completing malignant transformation, the high P-glycoprotein expression resulted in MIBI uptake on the second myocardial scintigraphy.