EXPRESSION OF CD34-ANTIGEN IN NASOPHARYNGEAL ANGIOFIBROMAS

Formalin-fixed, paraffin-embedded and frozen tissues of 24 patients wi th primary nasopharyngeal angiofibroma, of whom seven had recurrences, were studied immunohistochemically for the expression of CD34 antigen using two different antibodies (HPCA-1 and QBEND 10). In all cases, t here was an exclusive staining of endothelial cells, while pericytes, smooth muscle cells and stromal fibroblasts were not reactive. The sta ining intensity, however, was more pronounced in small tumor vessels o f capillary- and sinusoidal-type than in larger vessels, which were us ually characterized by an irregular smooth muscle coat. This different ial staining indicates an increased proliferative potential of the end othelium of the small vessel component of nasopharyngeal angiofibroma (neoangiogenesis) and an inhibitory influence of vascular smooth muscl e cells on endothelial cell growth. Moreover, the positive immunoreact ion of all endothelial cells for CD34 is indicative of the absence of lymphatic vessels, which confirms previous ultrastructural observation s. No differences in the staining pattern were observed between primar y versus recurrent tumors, formalin fixed, paraffin embedded versus sn ap-frozen acetone fixed material, or between both CD34 antibodies. Our findings indicate that nasopharyngeal angiofibroma is a vasoprolifera tive malformation. (C) 1998 Elsevier Science Ireland Ltd. All rights r eserved.