These initial results indicate that FET PET is a useful method to identify malignant brain lesions. It appears that high- and low-grade brain tumours exhibit a different uptake kinetics of FET. A kinetic analysis of FET PET may provide additional information in the differentiation of suspected brain lesions.

The presence of histological variants of haemangioblastoma is well established, but data on the prognostic implications of histological subtyping are missing. We thus characterized clinical factors associated with histological subtypes, that is, of the cellular and reticular variant of haemangioblastoma, in a series of 88 consecutive primary haemangioblastomas of the central nervous system. Ten haemangioblastomas were classified as 'cellular' according to Cushing and Bailey. As compared to the more common 'reticular' variant (n = 78), the proportion of tumours containing glial fibrillary acidic protein-positive tumour cells (80% vs. 7%), as well as median Ki67 (MIB1) proliferation indices [4% (quartiles: 1-8%) vs. < 1% (<1-2%)], was significantly higher in cellular haemangioblastomas (P < 0.01). Recurrences were more frequent in the cellular variant [2/8 (25%) vs. 4/51 (8%)]. Kaplan-Meier analysis confirmed a significantly higher probability of recurrence in the cellular variant (Log-Rank test P < 0.01). Cox regression analysis not only confirmed the well established association of von Hippel-Lindau disease with tumour recurrence (P < 0.01), but also revealed an independent effect of histological subtype on the probability of recurrence (P < 0.05), whereas no significant influence of age, sex or tumour location was observed. To conclude, the results from this retrospective study suggest that histological subtyping of haemangioblastomas has prognostic implications and might contribute to identify patients at risk for recurrence.

Histological findings, differential diagnosis and specific treatment are reviewed and discussed. Patients with PCG should be radiologically staged. Long term prognosis of PCG is good in cases surgically resectable. Nevertheless, patients require lifelong follow up.

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Using single-photon emission tomography (SPET), the radiopharmaceutical l-3-iodine-123-alpha-methyl tyrosine (IMT) has been applied to the imaging of amino acid transport into brain tumours. It was the aim of this study to investigate whether IMT SPET is capable of differentiating between high-grade gliomas, low-grade gliomas and non-neoplastic brain lesions. To this end, IMT uptake was determined in 53 patients using the triple-headed SPET camera MULTISPECT 3. Twenty-eight of these subjects suffered from high-grade gliomas (WHO grade III or IV), 12 from low-grade gliomas (WHO grade II), and 13 from non-neoplastic brain lesions, including lesions after effective therapy of a glioma (five cases), infarctions (four cases), inflammatory lesions (three cases) and traumatic haematoma (one case). IMT uptake was significantly higher in high-grade gliomas than in low-grade gliomas and non-neoplastic lesions. IMT uptake by low-grade gliomas was not significantly different from that by non-neoplastic lesions. Diagnostic sensitivity and specificity were 71% and 83% for differentiating high-grade from low-grade gliomas, 82% and 100% for distinguishing high-grade gliomas from non-neoplastic lesions, and 50% and 100% for discriminating low-grade gliomas from non-neoplastic lesions. Analogously to positron emission tomography with radioactively labelled amino acids and fluorine-18 deoxyglucose, IMT SPET may aid in differentiating high-grade gliomas from histologically benign brain tumours and non-neoplastic brain lesions; it is of only limited value in differentiating between non-neoplastic lesions and histologically benign brain tumours.