FDG-PET detection of primary lung cancer in a patient with an isolated cerebral metastasis.

Positron emission tomography (PET) is a new diagnostic technique. It is used to differentiate benign from malignant pulmonary nodules and to detect metastasis and lymph node involvement in primary lung cancer, but little has been published about its possible interest for detection of unknown primary tumors. We report the case of a man who underwent resection of a cerebral tumor. A histological diagnosis of cerebral metastasis from adenocarcinoma with a probable pulmonary origin was made. Preoperative staging (including thoracoabdominal CT-scan and bone scan) did not show any pathologic image, particularly in the thorax. A whole body FDG-PET-scan was then performed. An isolated (1.5 cm of diameter) hypermetabolic focus was discovered in the left upper lobe. Bronchoscopy was normal An upper left lobectomy confirmed the presence of the primary lung adenocarcinoma. In this particular case, FDG-PET proved to be a very useful diagnostic method. New indications are being developed for it.