Pathology International 2003; 53: 627–631 Blackwell Science, LtdOxford, UKPINPathology International1320-54632003 Japanese Society of PathologySeptember 2003539627631Case Report Retroperitoneal tumor and Kasabach–Merritt syndromeD. Brasanac et al . Correspondence: Dimitrije Brasanac, MD, PhD, Institute of Pathol- ogy, School of Medicine, University of Belgrade, Dr Subotica 1/II, 11000 Belgrade, Serbia and Montenegro. Email: saog@beotel.yu Received 17 October 2002. Accepted for publication 4 April 2003. Case Report Retroperitoneal kaposiform hemangioendothelioma with tufted angioma-like features in an infant with Kasabach–Merritt syndrome Dimitrije Brasanac, 1 Dragana Janic, 2 Ivan Boricic, 1 Nada Jovanovic 2 and Lidija Dokmanovic 2 1 Institute of Pathology, School of Medicine, University of Belgrade and 2 Department of Oncology and Hematology, University Children’s Hospital, Belgrade, Serbia and Montenegro Kasabach–Merritt syndrome denotes profound thrombocy- topenia and coagulopathy in an infant with a vascular tumor. A retroperitoneal vascular tumor with an unusual combination of histopathological features is reported, and compared with vascular lesions described in the reported cases of Kasabach–Merritt syndrome in the literature. A large retroperitoneal tumor that had expanded through the sigmoid mesocolon into the sigmoid colon wall was resected from an 8-month-old infant with fully developed Kasabach–Merritt syndrome. Histological examination revealed a combination of venous (cavernous) malforma- tion, kaposiform hemangioendothelioma and tufted angi- oma-like areas. Cellular tumor components (especially tufted angioma-like parts) infiltrated the wall of the sig- moid colon to the submucosal level. Immunohistochemical staining with antibodies to the Ki-67 antigen and proliferat- ing cell nuclear antigen showed a low proliferative activity, whereas the antiapoptotic bcl-2 protein was expressed diffusely in tumor cells. This is the first reported case of a vascular tumor with tufted angioma-like elements found in the retroperitoneum, and the first reported in combin- ation with kaposiform hemangioendothelioma and venous malformation in the same lesion. Considering the immu- nohistochemical results and overlapping histological fea- tures, it may be considered that tufted angioma and kaposiform hemangioendothelioma represent different growth patterns or stages in the development of a single type of hemangioma. Key words: kaposiform hemangioendothelioma, Kasabach– Merritt syndrome, retroperitoneum, tufted angioma Since the first case reported, 1 the term Kasabach–Merritt syndrome has been applied to an infant with profound throm- bocytopenia and coagulopathy as a consequence of heman- gioma. Besides a low platelet count, decreased plasma fibrinogen, an elevated D-dimer and a hemorrhagic tendency are usually found. Histopathological evaluation reveals vascular lesions that are often not classical capillary hemangioma but other types of vascular proliferations, such as tufted angioma (TA) or kaposiform hemangioendothe- lioma (KHE). 2–7 Tufted angioma 8 is restricted to superficial body parts, most commonly skin, while KHE 9 is usually found in the retroperitoneum and deep soft tissues, but can be located in the skin also. Both tumors may be associated with various vascular malformations, especially lymphatic. 2,4,10 We describe the case of an 8-month-old infant with Kasabach– Merritt syndrome and a retroperitoneal tumor extending through the sigmoid mesocolon into the sigmoid colon wall. CLINICAL SUMMARY An 8-month-old infant was admitted to hospital with high fever and vomiting that had started a few days earlier. The child weighed 8.3 kg, was extremely pale, and had numerous hematomas and purpura over the skin of the lower limbs. There was a huge palpable tumor located mostly on the left side of the abdomen. Laboratory analysis showed a low platelet count (18 ¥ 10 9 /L), increased D-dimer (8 mg/L) and decreased fibrinogen (0.33 g/L). Ultrasonography and com- puted tomography (CT) of the abdomen and pelvis disclosed a large multicystic tumor extending from the lower pole of the spleen down to the urinary bladder. On the second day after admission, the child’s platelet count dropped to 4.5 ¥ 10 9 /L. Two units of platelet concentrates twice a day and fresh frozen plasma 20 mL/kg once a day were given for four days until the thrombocytes increased to 254 ¥ 10 9 /L, and then surgery was performed. At operation, the tumor protruded from the retroperitoneal space into the sigmoid mesocolon and was attached to the wall of sigmoid colon. Partial exci-