Publication date: Sep 09, 2019
Despite classic teaching that intracranial metastases typically arise at the grey-white matter junction, small intracranial melanoma metastases (IMM) are frequently observed at the interface between the cortex and leptomeninges (i.e. “corticomeningeal interface”), suggesting possible leptomeningeal origin.
MRI brain examinations of melanoma patients treated at a specialist oncology centre from July 2015 to June 2017 were retrospectively reviewed. The MRI examination on which IMM were first visible was identified, utilising 1mm volumetric post-contrast imaging prior to local therapy. Individual metastases (up to 10 per patient) were assessed for the presence of leptomeningeal contact, as well as their number, size and morphology. Lesions ≥10mm in long axis were excluded, in order to examine early metastatic disease.
75 patients had evidence of IMM. 15 patients had only lesion(s) measuring ≥10mm at diagnosis, leaving 60 patients. 192 individual metastases were examined (median 2 per patient, interquartile range 1-4), 174 (91%) demonstrating leptomeningeal contact. A nodular morphology was observed in 154 of 192 (82%), 32 (17%) were ovoid but elongated along the cortex, and 6 (3%) were linear. Only three patients (5%) also exhibited a ‘classic’ linear leptomeningeal disease appearance.
Most IMM measuring between 2 and 9mm in diameter are corticomeningeal nodules. These data raise the hypothesis that deeper parenchymal extension of IMM occurs secondarily. If the leptomeninges provide a preferential site for establishment of IMM, further investigation of the underlying biology of this phenomenon may provide opportunities for novel therapeutic strategies for patients with IMM.
Lasocki, A., Khoo, C., Lau, P., Kok, D.L., and McArthur, G.A. High-resolution MRI demonstrates that more than ninety percent of small intracranial melanoma metastases develop in close relationship to the leptomeninges. 24057. 2019 Neuro Oncol.
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