35 YEAR‐OLD MAN WITH FALCINE TUMOR

CLINICAL HISTORY AND NEUROIMAGING

The patient is a previously healthy 35‐year‐old man who was admitted to our hospital for evaluation after experiencing vomitus, dizziness and headache for one month. A neurological examination elicited no abnormalities. CT and MR imaging were performed and revealed a 3.5 × 3.2 cm solitary, well‐delineated, extra‐axial midline mass arising from the frontal falx cerebri. The lesion was isointense to the cortex on T2 (Figure 1A) and hypointense on T1, with a marked homogenous enhancement after intravenous contrast administration (Figure 1B, 1C). Based on these findings, the radiological diagnosis was meningioma of the falx. At surgery, the tumour appeared as an extra‐axial lesion and was removed via a left midline frontal craniotomy. The excision was macroscopically complete.

Figure 1.

MACROSCOPIC FINDINGS

Macroscopically, the surgical specimen was whitish, soft, well circumscribed and measured 1.6 cm in diameter. Intraoperative pathological examination is not routinely performed during removal of meningiomas.

MICROSCOPIC FINDINGS

Microscopic features showed a neoplasm with high cellularity. The cells had irregular nuclei, the majority of which were naked, and in their midst were gemistocytic cells as well as pleomorphic cells with vescicular nuclei and abundant, eosinophilic cytoplasm. (Figure 2A). Mitotic figures were seen (3/10HPF), but without necrosis or microvascular proliferation. These cells laid in a fibrillary background. On immunohistochimical examination, the neoplasm was reactive for glial fibrillary acidic protein (GFAP—Figure 2B); MIB‐1 index was about 15% (Figure 2C). P53 protein was overexpressed (Figure 2D).

Figure 2.

What is the diagnosis?

DIAGNOSIS

Primary intracranial solitary leptomeningeal astrocytoma (WHO grade 3).

DISCUSSION

Primary intracranial solitary leptomeningeal astrocytoma (PLA) is very rare; it usually arises in the leptomeninges of the brain or spinal cord with no involvement of intraparenchymal tissue. PLA represent nests of glial tissue separated from the bulk of the CNS, which remain trapped in the leptomeningeal sheets, during embryogenesis, following an aberrant migration 1, 4. This form of astrocytoma differs from the more common secondary leptomeningeal astrocytoma, which refers to secondary spread from an intra‐axial glioma. PLA can present in two ways: a diffuse form that is macroscopically similar to meningitis, and a localized solitary form, that mimics other, more common, extra‐axial lesions, namely meningiomas.

Cooper and Kernohan criteria for a diagnosis of PLA are as follows: no attachment of meningeal tumor to the brain, no evidence of neoplasia within the brain, presence of leptomeningeal encapsulation around the tumour. All three criteria were satisfied in this case.

Concurrent adjacent meninigoma and astrocytoma has been described (2), but a retrospective analysis of the removed piece failed to detect any meningiomatous component of the lesion.

Fifteen cases of PLA are reported in the literature (3); the rarity of this pathological entity make this diagnosis a challenge on a neuroradiological basis. Notwithstanding, this challenge is of great importance since the diagnosis of astrocytoma versus meningioma implicates a notable difference both in prognosis and therapy. 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 appear to be straightforward radiological diagnoses.

ABSTRACT

A 35‐year‐old man presented with one month history of vomitus, dizziness and headache. CT and MR imaging revealed a 3.5 × 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.