Hyperostosis is the most common skull change associated with meningioma. Five hyperostosis cases of meningioma en plaque infiltrating the skull processed without previous decalcification of the bone tissue were investigated histologically and immunohistochemically with antibodies against somatostatin receptor 2A (SSR2A). Undecalcified bone biopsies embedded in methylmethacrylate and paraffin-embedded extraosseous tumor tissues were analyzed. All five cases were well-differentiated meningotheliomatous meningiomas en plaque according to the WHO classification of tumors and revealed areas of hyperosteoidosis. Furthermore, all five meningiomas en plaque presented strong positive reactions to antibodies against SSR2A in both the intraosseous and extraosseous tumor proliferates. In summary, similar morphological changes characterized by hyperosteoidosis were observed in a small cohort of meningioma en plaque associated with expression of SSR2A and reports in the literature of the histogenesis of hyperostosis in meningioma en plaque are discussed.
