Expression of phosphodiesterase-5 in lymphatic malformation tissue.

Expression of Phosphodiesterase-5 in Lymphatic Malformation Tissue Lymphatic malformations (LMs) are uncommon and sometimesdebilitating congenital vascular anomalies that presumably arise because of developmental dysplasia of the lymphatic network in utero. They comprise primitive lymphatic sacs surroundedby a thickened layer of connective tissue and interspersedmuscle fibers.1 Current treatments forLMarepalliative and only partially successful and include compression, surgical resection, laser ablation, andsclerotherapy.A recent report by Swetman and colleagues2 noted marked reductions inLMsize in3childrenafter starting treatmentwith oral sildenafil citrate, an inhibitor of phosphodiesterase isoform 5 (PDE5). The localization of PDE5 in LM tissue and the mechanism of the effect of sildenafil on LM is unknown. To further investigatePDE5 localizationwithinLMtissue,weperformed immunohistochemical studies to identify the presence and relative location of PDE5 expression in vascular smooth muscle, vascular endothelium, and lymphatic endothelium.