Pigmented lesion of the central nervous system: what is it?

Meningiomas are the most common primary central nervous system (CNS) neoplasms in adults, arising from arachnoid cells as extra-axial tumours.We report a rare case of World Health Organization (WHO) grade 2 metaplastic meningioma with lipomatous differentiation in a 70-year-old man presenting with persistent headaches.Magnetic resonance imaging revealed a dyshomogeneous left parieto-occipital extra-axial mass with calcific components and dural thickening suggestive of infiltration, confirmed histologically by brain parenchyma invasion, atypical cell proliferation with hemosiderin-containing brownish pigmentation (Prussian blue-positive), and lipoblast-like elements.Immunohistochemistry showed positivity for epithelial membrane antigen and progesterone receptor, with negativity for S100, glial fibrillary acidic protein, and Olig2, confirming meningothelial lineage and excluding melanocytic or glial neoplasms.According to WHO CNS 2021, brain parenchyma invasion warranted a grade 2 designation; however, the prognostic implications of this criterion in metaplastic meningioma remain to be fully established.