Capillary-lymphatic malformation, kaposiform hemangioendothelioma and delayed Kasabach-Merritt phenomenon

According to International Society for the Study of Vascular Anomalies classification, vascular anomalies are mainly divided into two groups: vascular tumors and vascular malformations. Nevertheless, a small group of patients present clinical and/or histopathologic overlapping features. We report a case of a 4-month-old boy that presented a vascular lesion on his right buttock with involvement of abdominal wall muscles, abdominal cavity and drainage to primitive iliac by a tortuous drainage vein. Surgery was performed and histopathology demonstrated a combined vascular malformation. Six months later he developed a thrombocytopenia and repeat magnetic resonance imaging revealed a new solid mass involving the majority of the abdominal cavity. At 18 months of age the patient developed a Kasabach-Merrit phenomenon and treatment with vincristine, interferon and then acetyl-salicilic acid and dypiridamol was started. No response in platelet counts was obtained and one more surgery was perfomed. On this occasion a histopathologic study revealed vascular malformation areas intermingled with areas of kaposiform hemangioendothelioma. This patient demonstrates the Kasabach-Merritt phenomenon with kaposiform hemangioendothelioma arising within a pre-existing combined vascular malformation.