Summary
Aims: Juvenile nasopharyngeal angiofibroma (JNA) is a rare tumour occurring almost exclusively in young adult males. Although histologically benign, it can be locally aggressive with a significant recurrence rate. The finding of activating beta-catenin gene mutations in the stromal cells indicates these are the neoplastic cells and supports the association of JNA and familial adenomatous polyposis (FAP). Previous immunohistochemical studies have demonstrated a null or focal myoepithelial immunophenotype in the stromal cells. Recently, expression of several growth factors and oncoproteins including CD117 (c-kit) in the stromal cells has been demonstrated. Our objective is to evaluate the immunohistochemical phenotype of the stromal cell of JNA, particularly within the proliferative zone of the tumour, by application of antibodies against MNF116, CAM5.2, S-100, CD31, CD34, CD99, CD68, vimentin, EMA, SMA, desmin, calponin, Bcl-2 and (CD117) c-kit in a series of 54 cases.
Methods: A routine immunohistochemical protocol was applied to representative paraffin sections of 54 JNAs collected from the Port Moresby General Hospital, Papua New Guinea, and Princess Alexandra and Royal Brisbane Hospitals, Queensland, Australia. Immunoexpression of each antigen was assessed in the stromal cells and the vessels.
Results: The majority of stromal cells in more than half of the cases demonstrated no staining with any of the 14 antibodies other than vimentin. Of 54 cases, 22 contained a microvascular component (usually peripherally located and indicating the active growth front of the tumour) in which the stromal cells demonstrated a hybrid immunophenotype with both smooth muscle and endothelial differentiation. c-kit was negative in all cases.
Conclusions: The majority of stromal cells have an undifferentiated immunophenotype with no evidence of epithelial, myoid, endothelial or other lineage specific differentiation. In the microvascular component the stromal cells appear able to show smooth muscle or endothelial differentiation. No c-kit expression was identified.