[Role of master transcriptional factor Prox-1 in lymphatic endothelial differentiation of Kaposiform hemangioendothelioma].

Objective: To analyze the clinical and pathological features of Kaposiform hemangioendothelioma (KHE), and to investigate the role of master transcriptional factor Prox-1 in the regulation of lymphatic differentiation. Methods: Nine cases of KHE (during the period from October 2009 to June 2016) were collected with clinical and pathological data. H&E stained section review and immunohistochemietry using the Dako EnVision method were performed. Results: There were 6 female and 3 male patients with age ranging from 2 months to 8 years (median 3 years and 4 months). The patients presented with either single subcutaneous soft tissue mass, or bone tumors, with the duration of disease onset ranging from 1 month to 1 year. The sites of involvement included the skins of neck (2 cases), nose root (1 case), inguinal (1 case), thigh root (1 case), humerus (2 cases), lumbar vertebrae(1 case), and mesentery (1 case). These tumors were histologically composed of nodules of densely packed spindle or ovoid cells and deformed small blood vessels in an invasive growth pattern. The tumor cells were immunohistochemically positive for both blood vessels and lymphatic endothelial markers, including Prox-1, the master transcriptional factor, and VEGFR-3. With followed-up from 1 to 60 months (median 26 months), two patients died of the disease, while the remaining patients were alive without recurrence. Conclusions: KHE is a rare vascular tumor with at least partial lymphatic endothelial differentiation, in which Prox-1 may act as a master regulator for such differentiation. KHE is an aggressive tumor of intermediate malignant potential, with local invasion and recurrence tendency, and long term follow-up is required.