A 35-year-old man presented with one month history of vomitus, dizziness and headache. CT and MR imaging revealed a 3.5 x 3.2 cm solitary extra-axial midline mass arising from the frontal falx cerebri; radiological findings were diagnostic of meningioma of the falx. At surgery, the tumour appeared as an extra-axial lesion and was removed via a left midline frontal craniotomy. Macroscopically, the surgical specimen was whitish, soft, well circumscribed and measured 1.6 cm in diameter; microscopic features showed a neoplasm with high cellularity, presence of mitotic figures, without necrosis or microvascular proliferation; the neoplasm was reactive for glial fibrillary acidic protein and MIB-1 index was about 15%. Given the localization, microscopic features were diagnostic of primary intracranial solitary leptomeningeal astrocytoma (PLA), WHO grade 3. PLA is a very rare lesion that arises in the leptomeninges of the brain or spinal cord with no involvement of intraparenchymatous tissue. Fifteen cases of PLA are reported in the literature. Retrospective neuroradiological analysis of this case failed to detect any findings to help in the differential diagnosis, thus confirming the fundamental role of the neuropathologist even in what can firstly appear to be a straightforward radiological diagnosis.