A False Positive Lung Scan In A Middle Aged Man Due To Encasement Of Pulmonary Vasculature By Atypical Mediastinal Carinoid Tumour Demonstrated On SPECT/CT

Encasement of the arterial pulmonary vascular bed is a recognized, albeit uncommon, cause for false positive results in ventilation/perfusion imaging. We present a case of a 49 year-old man with a history of atypical mediastinal carcinoid tumour of unknown primary who had a false positive ventilation/perfusion lung scan, which was shown by C.T. P.A. (computed tomographic pulmonary angiogram) to be due to selective encasement of the pulmonary vessels. The accurate diagnosis prevented inappropriate anticoagulation and the patient was managed symptomatically.