Hemangioendotheliomas are benign vascular mesenchymal tumors that present in infancy [usually before 6 months] and may pose problems due to ensuing complications. The liver is the organ most commonly involved; however splenic, tracheal, pulmonary, GI tract, thymic, pancreatic and meningeal involvement have been reported. These patients may also present with cutaneous hemangiomas. Histologically these tumors are anastomosing arterio-venous channels lined by endothelial cells.
The neonate may present with asymptomatic hepatomegaly or with complications such as high output cardiac failure, consumptive coagulopathy with thrombocytopenia [Kasabach - Merritt syndrome], disseminated intravascular coagulation, anemia, and encroachment of the surrounding tissues. These tumors, if small, usually involute spontaneously; however patients may succumb to complications. Extremely rare cases of malignant conversion to angiosarcoma have also been reported.
Ultrasound is the initial imaging modality almost always employed to diagnose this infantile hepatic tumor. Hemangioendotheliomas have a varied appearance ranging from a solitary solid-appearing lesion to a multifocal variegated cystic mass. Ultrasound can accurately arrive at a diagnosis if the vascular cystic component is the predominant feature. High intratumoral flow may be apparent on Doppler. The cystic spaces may be vascular and may completely fill with color on Doppler examination or may represent areas of cystic necrosis. Additional imaging may be required to confirm the diagnosis and is commonly performed with CT to fully determine the extent of the lesion. Sometimes calcifications may be seen in the mass. If the hepatic tumor is large enough, a prenatal diagnosis can also be made, with the tumor appearing as a highly echogenic lesion in the liver.
CT scan appearance has been described the tumor appearing as a hypo- isodense mass, showing significant post contrast enhancement. MRI and nuclear scans can also be performed. Since most of these patients are managed on a medical basis [treated with steroids], follow up volume imaging of these tumors and its perfusion will be necessary, underscoring the importance of careful pretreatment measurements.
Hepatic mesenchymal hamartoma forms the closest differential for this cystic mass. It is important to differentiate it from a hemangioendothelioma, as the former warrants surgery for definitive treatment. On sonography, a hamartoma may appear as a non-specific multicystic mass, with the cysts filled with clear or gelatinous fluid. But a highly vascular mass favors the possibility of a hemangioendothelioma. Sometimes though, only histology can distinguish the two entities.