Intracranial kaposiform hemangioendothelioma: proposal of a new malignant variant.

Kaposiform hemangioendothelioma (KHE) is a rare vascular tumor of infancy and early childhood that occurs mainly in soft tissue and the retroperitoneum. The pathological characteristics of a KHE are fascicles of spindleshaped endothelial cells and slitlike vascular channels with irregular tumor margins. In spite of benign features such as rare mitoses and a low MIB-1 labeling index, a KHE is categorized as an intermediate malignancy because of local invasiveness into adjacent lymph nodes or organs. Resection is the treatment of choice for this type of tumor and adjuvant medical therapy is prepared for the tumor remnants and the associated Kasabach-Merritt syndrome. In this paper the authors report a case of a KHE without Kasabach-Merritt syndrome arising from the right tentorium cerebelli in a 13-month-old male child. The biological behavior of the tumor, including its pathological traits and clinical course, was malignant in nature. This case may be not only the first intracranial extraaxial KHE, but also the first truly malignant variant. Kaposiform hemangioendothelioma should be considered in the differential diagnosis of intracranial and extraaxial tumors.