P06.10 * MAST CELL CONTENT IN ANGIOMATOUS MENINGIOMA IN COMPARISON WITH OTHER MENINGIOMA SUBTYPES

Abstract

We report here that angiomatous meningioma exhibit elevated numbers of mast cells within their tissue architecture compared to most other meningioma subgroups, but similar to the so-called secretory variety of this tumour type. This finding might help to understand the development of the vascular component of this neoplasm and might equally be helpful in diagnosing such tumours, since diagnostic criteria are by no means clear: The (WHO-) definition of the entity states, that angiomatous meningioma is a tumour that exhibits numerous blood vessels on the background of a typical meningioma. But the quantitative aspect i.e. the percentage of vasculature required for this diagnosis is not specified. Our analysis of 27 angiomatous meningiomas revealed a mast cell density of 0.32 % of all tumour cells. This is a significant increase (α = 0.05, U-test) compared to an unselected sample of meningiomas of various, mostly endotheliomatous specimens (0.13 %). This finding relates angiomatous meningiomas to the similarly highly vascular secretory variant, that presents with an even higher percentage of mast cells (1.11 %). This latter subgroup, however, is well defined by the occurrence of secretory products, whereas angiomatous meningioma in other and our samples present with at least two morphological types, microvascular and macrovascular. Single cases of angiomatous as well as secretory meningiomas may therefore produce abundant intracranial edema. The microvascular subtype of angiomatous meningioma is very similar to the so-called mircrocystic variety of meningeal tumors. Thus, the similarity between both on one side (general morphology) as well as the common occurrence of mast cells, prominent vasculature and increased edema formation in angiomatous and secretory meningiomas raises the question of the rationale of meningioma subtyping. In this respect, descriptive morphological analysis may yield significant results.