Expression of PROX ‐1 in oral K aposi's sarcoma spindle cells

Background The histogenesis of neoplastic spindle cells of K aposi's sarcoma is still uncertain, but some studies consider it a lymphatic vessel differentiation. Prox‐1 is a nuclear transcription factor that plays a major role during embryonic lymphangiogenesis, and it has been considered a specific and sensitive lymphatic endothelial cell marker. The aim of this study was to determine the expression of P rox‐1 in oral K aposi's sarcoma comparing the results with oral benign vascular tumors including capillary hemangiomas and pyogenic granulomas. Methods Expression of P rox‐1 and HHV ‐8 was evaluated by immunohistochemistry in 30 oral K aposi's sarcoma, 5 oral capillary hemangiomas, and 10 oral pyogenic granulomas. The labeling index was expressed as the percentage of positive cells for each case studied. Statistical comparison was performed using the W ilcoxon– M ann– W hitney rank sum test. Results Twenty‐eight (93.3%) and 30 oral K aposi's sarcoma cases were positive for P rox‐1 and HHV ‐8, respectively, while all oral benign vascular tumors were negative for these markers. The number of P rox‐1 and HHV ‐8 oral K aposi's sarcoma‐positive cells increased significantly from patch/plaque to nodular histological stages. Conclusion The expression of P rox‐1 in the neoplastic spindle cells supports the view of a lymphatic differentiation in oral K aposi's sarcoma. Prox‐1 may also be involved in the pathogenesis of oral K aposi's sarcoma as the number of positive spindle cells increased progressively from patch to nodular stages and could be eventually useful as an additional diagnostic tool for differential diagnosis between oral K aposi's sarcoma and benign oral vascular lesions.