Article
Low uptake of [18F]FDG-PET in primary central nervous system lymphoma: Two cases report
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Published: | May 8, 2006 |
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Objective: Primary central nervous system lymphoma (PCNSL) has a characteristic findings in 18F-fluorodeoxyglucose positron emission tomography ([18F]FDG-PET). It is a useful tool to diagnose PCNSL showing a huge accumulation of FDG on the tumor. However, FDG is not perfect and there are limitations to its use; high physiological uptake, benign conditions with increased glycolysis such as infection, inflammation. Our PCNSL patients did not display a increase in FDG uptake compared with the normal lesion. This report proposes 2 cases with low uptake of the [18F]FDG-PET in unusual diffusely infiltrating PCNSL.
Results: Case 1: A 75-year-old-man had rapidly progressive dementia over 2 months. T2-weighted MR image of the head showed increased signal intensity in deep white matter of both cerebral hemispheres. Enhancement was little after administration of contrast material. He did not show a significant increase in FDG uptake. The diagnosis was made by biopsy of the right superior temporal gyrus and pathological specimens were positive for anaplastic large T cell lymphoma. The patient received whole brain irradiation of 46Gy and a focal brain boost 14Gy.
Case 2: A 14 year-old-man had rapidly progressive right hemiparesis over 2 weeks. T2-weighted MR image of the head showed increased signal intensity in white matter of left frontal and temporal lobe. Enhancement was little after administration of contrast material. He did not show a significant increase in FDG uptake. The diagnosis was made by open biopsy and pathological specimens were positive for malignant large- cell lymphoma, B-cell phenotype.the patient received mainly high-dose methotrexate chemotherapy.
Conclusions: An [18F]FDG-PET is a useful to diagnose PCNSL. But our 2 cases that a diffusely infiltrating PCNSL showed low uptake of [18F]FDG-PET. It may be in relation to cellular density. These cases are easily mistaken on MRI or PET findings for other conditions that cause infectious, inflammatory or neurodegenerative etiologies. In this condition, we propose that biopsy should be done immediately.