[Detection of unknown primary tumor in a patient with cerebellar metastasis using FDG PET-CT: case report]

Identification of unknown primary tumors in patients with brain metastasis is a continued diagnostic challenge. Several clinical reports have suggested that 18F-flouorodeoxyglucose positron emission tomography (FDG PET) is useful for detecting them. PET has incomparable abilities to determine the metabolic activity of tissues. But it needs the assistance of higher-resolution, anatomic information. CT is the easiest and highest-resolution tomographic modality to be integrated into PET imaging. Because of this, the market for PET devices has shifted so dramatically toward PET-CT. We report a case to show that FDG PET-CT was able to detect an unknown primary tumor. A 75-year-old female underwent resection of a left cerebellar tumor. The histological diagnosis was adenocarcinoma metastasis. Conventional systemic evaluation (chest radiography, chest and abdomen CT, abdominal sonography, and so on) did not show any pathologic image. FDG PET-CT was then carried out. A hypermetabolic focus was revealed in the left hilum. In conclusion, from now on, FDG PET-CT will be considered as the first diagnostic process for patients presenting brain metastasis with an unknown primary tumor.