Brain 18F-choline PET/CT in primary diffuse leptomeningeal melanomatosis

Excerpt

A 55-year-old man presented with progressive asthenia, nausea, and headache since 6 months. Blood analysis showed no abnormalities apart from elevated prostate-specific antigen (PSA) levels (30 μg/L, normal <4 μg/L). A diagnosis of prostate adenocarcinoma was made based on radiological examinations and prostate biopsy, treated by radical prostatectomy. However, asthenia, nausea, and headache persisted and progressively worsened. Clinical examination, including complete skin examination, was normal. Brain magnetic resonance imaging (MRI) showed diffuse subarachnoid hyperintensities on fluid-attenuated inversion recovery (FLAIR) sequence and left frontotemporal subarachnoid hyperintensity on T1-weighted imaging (Fig. 1). Brain and spinal MRI revealed diffuse leptomeningeal enhancement on gadolinium-enhanced T1-weighted imaging. Repeated cerebrospinal fluid (CSF) analyses (n = 5) showed mild lymphocytic pleocytosis (range 2–15/mm³), elevated protein levels (range 1.47–1.81 g/L), and the presence of malignant cells (although the precise origin of the underlying malignancy could not determined). Blood and CSF PSA levels were undetectable. A CT of the thorax and abdomen and both brain and whole body 18F-FDG PET/CT did not show meaningful abnormalities. Brain 18F-Choline PET/CT, performed in search of brain metastasis from prostate cancer, showed hypermetabolic foci in the left frontotemporal area (SUVmax 2.3) corresponding to the MRI T1 hyperintensity. A left temporal meningeal biopsy showed leptomeningeal melanomatosis. A diagnosis of primary diffuse leptomeningeal melanomatosis was made. Oral temozolomide treatment (150 mg/m², od, during 5 days, monthly) was started.

…