Mast cells and T-lymphocytes in juvenile angiofibromas

Juvenile angiofibroma (JA) is regarded as a benign fibrovascular tumour of unknown aetiology. Due to its fibrovascular architecture the fibrous and vascular tumour component have been in the focus of most studies. This investigation aimed at characterizing inflammatory cells in JAs by immunohistochemical stainings and western blot analysis. Number and type of mast cells as well as T-lymphocytes were evaluated in a series of 10 JAs and 5 nasal mucosa (NM) specimens used as control tissue. A remarkable number of mast cells were found in JAs (14.6% of all cells). By using a combination of the mast cell markers tryptase and chymase three distinct mast cell populations could be identified: 12% expressed tryptase (T+) only, 3% stained for chymase (C+) only, and 85% were positive for both tryptase and chymase (TC+). Western blot analysis supported finding of remarkable expression of the mast cell markers tryptase and chymase in JAs and indicated for both proteins similar but also different molecular weights than being observed in NM. Furthermore an infiltration of the tumour by CD4- and CD8-positive T-lymphocytes (15.4% of all cells) was evident in immunofluorescent stainings. Compared to NM, a significantly higher number of TC+ (6.9% in JAs versus 2.7% in NM) and CD8-postive (9.7% in JAs versus 5.8% in NM) cells were found in the tumour tissue. Thus, mast cells and T-lymphocytes were identified as predominant cell types in JAs representing 30% of the cells in the tumour specimens analysed. Regarding these observations JAs are certainly not only built up by vascular cells and fibrous stroma cells. High rates of inflammatory cells like mast cells and T-lymphocytes have to be considered in this tumour.