Meningioma with trabecular architecture: a harbinger of BAP1 deficiency.

BRCA (BReast CAncer gene)-associated protein 1 (BAP1) is a tumor suppressor protein encoded by the BAP1 gene. BAP1 mutations and the loss of BAP1 expression on immunohistochemistry are poor prognostic factors for meningiomas. These mutations have been previously reported in papillary and rhabdoid meningiomas. However, BAP1-deficient meningiomas with a trabecular architecture are rare, with only one previous report describing two cases. Here, we present the case of an 80-year-old male who experienced two recurrences of meningiomas over a 14-year period. The initial tumor exhibited a mixture of typical meningothelial meningioma and meningioma with trabecular architecture, whereas the second recurrence was almost entirely trabecular. Immunohistochemical analysis revealed a BAP1 deficiency. This case highlights the importance of the trabecular architecture as a histological pattern that may indicate BAP1 loss and poor prognosis. Given the potential for targeted therapies, further research is needed to establish this histological subtype as an independent entity with poor prognosis.