Aquaporin-4 expression in primary human central nervous system lymphomas correlates with tumour cell proliferation and phenotypic heterogeneity of the vessel wall

No literature data are available concerning the expression of aquaporin-4 in primary central nervous system lymphomas and the relationship between aquaporin-4 expression and the morphological characteristics of blood vessels. Here, we have investigated this relationship in 24 human diffuse large B-cell primary central nervous system lymphomas by means of immunocytochemistry and confocal laser microscopy. Results have shown that: (i) a high aquaporin-4 expression correlated with a high Ki-67 index and aquaporin-4 marked tumour and endothelial cells in cytoplasm and plasma membranes, while aquaporin-4 expression was low in tumour areas with a low Ki-67 index where few tumour cells were positive to aquaporin-4, and endothelial cells showed aquaporin-4 expression on their abluminal side. (ii) Different type of cells participated in vessels formation: CD20 ⁺ tumour cells and factor VIII ⁺ endothelial cells; aquaporin-4 ⁺ tumour cells and CD31 ⁺ endothelial cells; CD20 ⁺ and aquaporin-4 ⁺ tumour cells; glial fibrillary acidid protein ⁺ endothelial cells surrounded by glial fibrillary acidic protein ⁺ tumour cells. Overall, these data suggest the importance of aquaporin-4 in primary central nervous system lymphomas due to its involvement in cerebral oedema formation and resolution and tumour cell migratory activity, and have documented that tumour microvasculature in lymphomas is extremely heterogeneous, confirming the importance of neoangiogenesis in the pathogenesis of lymphomas.