Kaposiform haemangioendothelioma: a review with emphasis on histological differential diagnosis.

Kaposiform haemangioendothelioma (KHE) is a rare, locally aggressive/borderline vascular tumour primarily seen in neonates and children. KHE is occasionally associated with Kasabach-Merritt phenomenon and tends to have a poor clinical prognosis. While the histological features of tufted angiomas and KHE overlap, some believe tufted angiomas are a milder, benign, more localised counterpart of KHE. The other histological differential diagnoses of KHE include infantile haemangioma, congenital haemangioma, spindle cell haemangioma, verrucous malformation/haemangioma, and Kaposi sarcoma. Microscopically, KHE is characterised by confluent nodules of neoplastic spindled endothelial cells involving multiple planes of tissue which are positive for endothelial, lymphatic, and smooth muscle markers. Resection, once thought to be the definitive treatment for KHE, is often unattainable due to the extent of the lesion; thus, single or combination chemotherapies have been used to treat these patients. Sirolimus has recently been reported to be a successful agent to treat refractory and complicated cases of KHE.