Meningiomas with Collagenous Rosettes: A Report of Three Cases

Formation of rosettes is very rarely encountered in meningiomas. The 2016 WHO classification of central nervous system tumors mentions it as a rare pattern secondarily encountered in different variants. We report three cases of meningiomas forming collagenous rosettes. Case 1 was a 60-year-old male with a right frontoparietal mass lesion. Excisional biopsy showed features of atypical meningioma (WHO Grade II) with diffusely scattered collagenous rosettes. Case 2 was a 48-year-old male with right frontoparietal space-occupying lesion. Microscopy revealed a papillary variant of meningioma (WHO Grade III) with prominent diffusely scattered collagenous rosettes. Case 3 was a 75-year-old female with left parietal convexity tumor. Microscopy revealed a clear-cell meningioma (WHO Grade II) with cerebral invasion. Focal collagenous rosettes and fibrosclerotic whorls were noted. In all three cases, Masson's trichrome was used to confirm collagenous nature of the rosettes. All three tumors were positive for epithelial membrane antigen and vimentin.