Kaposiform hemangioendothelioma complicated by Kasabach-Merritt phenomenon: ultrastructural observation and immunohistochemistry staining reveal the trapping of blood components.

Kaposiform hemangioendothelioma (KHE), a borderline tumor of endothelial origin, is associated with Kasabach-Merritt phenomenon, characterized by profound thrombocytopenia and consumptive coagulopathy resulting from the localized intravascular coagulation (LIC) in the tumor. Previous studies have suggested that the trapping of blood components, including platelets, may underlie the LIC in KHE. However, more evidence is needed to support this hypothesis. In this study, one case of a Chinese infant with a KHE in the left arm was complicated by Kasabach-Merritt phenomenon. The tumor was partially resected and the sample was used for ultrastructural observation and immunohistochemistry staining of Glut-1. Ultrastructural observation found the trapping of erythrocytes, platelets, macrophages, and lymphocytes in the slit-like channels of the tumor nodules, and phagocytic vesicles in the cytoplasm of neoplastic cells. Immunohistochemistry staining further showed numerous Glut-1(+) erythrocytes in the channels. In conclusion, our results provided compelling morphological evidence of the trapping of blood components in KHE, which may interpret the LIC in the tumor and subsequent consumptive coagulopathy.