A Case of Kaposiform Hemangioendothelioma and Kasabach‐Merritt Phenomenon

Kaposiform hemangioendothelioma (KH) is a vascular tumor of intermediate malignancy that occurs in childhood, of which 50% are present at birth. The tumor has a predilection for the trunk, extremities, and retroperitoneum. It is commonly associated with Kasabach‐Merritt phenomenon, a consumptive coagulopathy characterized by profound thrombocytopenia and hypofibrinogenemia. The histologic differential diagnosis of kaposiform hemangioendothelioma includes infantile hemangioma, tufted angioma, Kaposi's sarcoma, and spindle cell hemangioendothelioma. We present a case of a neonate with a soft tissue mass encompassing the proximal two‐thirds of the right thigh. After delivery by Ceasarean section for failure to progress, the patient developed repiratory failure, consumptive coagulopathy and intracranial hemorrhage. The initial clinical differential diagnosis included KH, infantile hemangioma, and infantile fibrosarcoma, all entities which have been associated with Kasabach‐Merritt phenomenon. An biopsy demonstrated a nodular vascular proliferation composed of grouped, spindled endothelial cells forming irregular, slit‐like vascular lumens. There were associated fragmented red blood cells and hemosiderin deposits. The tumor cells were focally positive for D2–40, an antigen specific for lymphatic endothelium and expressed by KH, and were negative for GLUT‐1, an antigen expressed in infantile hemangiomas but not KH. The histologic and immunohistochemical findings confirmed the diagnosis of KH.