No abstract

Positron emission tomography (PET) studies have been performed using 18-F-fluorodeoxyglucose in 29 adult subjects with primary brain tumors. Seventy-two percent of the patients were treated previously. The glucose metabolic state in the lesions was increased in 16 patients, and was normal or decreased in 13 patients. The hypermetabolic tumors tended to behave in a more malignant fashion. Patients with hypermetabolic tumors had a median survival of 7 months after PET scan, compared to 33 months for those with hypometabolic lesions. Among the high-grade glioma patients, the PET results separated them into a good prognosis group (hypometabolic, with 78% 1-year survival) and a poor prognosis group (hypermetabolic, with a 29% 1-year survival after PET). These results suggest that glucose metabolic studies may provide an independent measure of the aggressiveness of a brain tumor, and may supplement pathologic grading.

Pulmonary infection or inflammation might predispose patients to localized F-18 FDG chest uptake mimicking pulmonary metastases and limiting the specificity of whole-body scans performed in patients with cancer.

Two patients are described who showed abnormal fluorine-18 fluorodeoxyglucose (F-18 FDG) uptake that was due to benign disease, specifically tuberculous lymphadenitis and pneumonitis. The first patient had ulceration and oozing of the left nipple that was related to Paget's disease. An F-18 FDG PET, whole-body scan, which was performed for staging, showed no breast uptake. However, there was intense multifocal uptake in mediastinal, supraclavicular, and para-aortic areas that was confirmed radiologically to represent widespread lymphadenopathy. Pathologic examination of a mediastinal lymph node showed active tuberculosis. The second patient showed intense focal F-18 FDG uptake in mediastinal and supraclavicular areas and para-aortic lymphadenopathy due to non-Hodgkin's lymphoma. In addition, there was abnormal F-18 FDG lung uptake that revealed the presence of acid-fast bacilli on bronchial lavage. Intense focal F-18 FDG uptake in widespread lymphadenopathy or in the lung could be caused by infectious diseases such as tuberculosis. This possibility should be considered when whole-body scans of patients with cancer are interpreted, especially in those with a high incidence of infectious disease.

A 33-year-old woman presented with a 3-year history of progressive numbness in the hand, cerebellar ataxia, limb weakness, nystagmus, and dysarthria. T2-weighted MRI revealed abnormal foci of increased signal intensity mimicking demyelinating plaques in the periventricular white matter, and brain 18FDG-PET scan showed increased uptake in the pons. Biopsy from a tibial lesion showed aggregates of foamy histiocytes in the intertrabecular spaces replacing the bone marrow, characteristic of Erdheim-Chester disease. The patient was treated with craniospinal radiation. After 6 months, the clinical picture was stable and the MRI was unchanged.