Simultaneous FDG PET+/Glut1+ lung and FDG PET-/Glut1- subcarinal lymph node metastases from prostate cancer

A 78-year-old man with a history of prostate cancer and a rise in PSA presented with a new left lung mass, detected on computed tomography (CT). Positron emission tomography (PET)-CT (PET-CT) scan with 18-F fluorodeoxyglucose glucose revealed intense uptake in the lung mass without any other areas of abnormal uptake. Surgical resection of the mass and mediastinal lymph node dissection revealed metastatic adenocarcinoma from prostate cancer in the left lung mass (tumor size 5 cm) as well as in a subcarinal lymph node (tumor size 1.9 cm), which were identical on hematoxylin and eosin stains with a Gleason score of 8. The size of the subcarinal lymph node metastasis could not explain its non-visualization on PET. Glut1 stains of the lung mass were positive with moderate (2+ out of maximum 3+) reactivity in 95% of the carcinoma cells, whereas Glut1 stains of the subcarinal lymph node were negative with faint (1+ out of maximum 3+) reactivity in ca. 30% of the carcinoma cells. The low Glut1 expression in the subcarinal lymph node is the most likely explanation for its non-visualization on PET.