Histopathology of vascular lesions found in Kasabach-Merritt syndrome: Review based on 13 cases

We reviewed the histopathology of 13 cases of Kasabach-Merrit Syndrome (KMS ). In 4 (31%) cases the predominant morphology was that of a tufted angioma (TA). Six (46%) cases were Kaposiform hemangioendotheliomas (KHE), and 3 ( 23%) cases showed an infantile (juvenile) hemangioma only. Immunostaining f or CD34 and actin (HHF-35) was helpful in defining these types of hemangiom as. The TA was characterized by a proliferation of endothelial cells positi ve for CD34 with a minimal component of actin-positive cells. KHE showed a paucity of immunoreactive cells, only the luminal endothelial cells were po sitive for CD34. In three cases with the morphology of infantile hemangioma s, actin-positive cells out numbered the CD34-positive cells. Our findings confirm the observation that the underlying vascular lesion in KMS is usual ly not an infantile hemangioma as was originally thought, but variants of h emangiomas such as TA and KHE (77% of 13 KMS cases). Infantile hemangioma w as the phenotypic substrate of KMS in only 3 of 13 cases.