Discussion

Kaposiform hemangioendothelioma is a kind of borderline vascular tumour of endothelial origin with local invasion ^{Reference Gómez-Villegas, Pérez-Téllez and Ochoa-Gaviria4} that has the dual characteristics of haemangioma and Kaposi’s sarcoma. ^{Reference Fernández, Bernabeu-Wittel and García-Morillo5} In 1993, Zukerberg ^{Reference Zukerberg, Nickoloff and Weiss6} and others first described and coined the term “kaposiform hemangioendothelioma.” In 2014, the International Society for the Study of Vascular Abnormality (ISSVA) classified it as a “locally invasive or borderline vascular tumour.” ^{Reference Dasgupta and Fishman7}

Kaposiform hemangioendothelioma is very rare but when diagnosed, it is usually in infants and children. ^{Reference Filippi, Tamburini and Berti8} This disease often occurs in the skin and deep soft tissues of the limbs, upper torso, and maxillofacial region. ^{Reference Zhang and Dong9} This case occurred in the heart, a rare manifestation, and recently has been successfully treated by surgery and sirolimus. The pathogenesis of this disease is still unclear, and it may be related to chromosome abnormalities. ^{Reference Zhou, Wang and Panossian10} The main clinical manifestations of cardiac kaposiform hemangioendothelioma are dyspnoea and tachypnoea. Kaposiform hemangioendothelioma grows, and surrounding tissues of the tumour are often invaded. It does not regress spontaneously, and it may be accompanied by regional lymph node metastases, but distant metastatic spread is rare, with only one case reported. ^{Reference Ren and Li11,Reference Mota, Scaranti, Fonseca and etal12}

Kaposiform hemangioendothelioma is often non-specific on laboratory investigations. If it is accompanied by the Kasabach–Merritt phenomenon, there may be some abnormalities, such as thrombocytopenia, fibrinogen decrease, and D-dimer increase. Studies have shown that approximately 71% of kaposiform hemangioendotheliomas can develop into Kasabach–Merritt syndrome. In this study, two of the four children were accompanied by the Kasabach–Merritt phenomenon. ^{Reference Walsh, Carcao and Pope1–Reference Zaidi, Shaik and Agrawal3} According to statistics, the Kasabach–Merritt phenomenon is the main cause of death in sick children, with mortality rate up to 30%. ^{Reference Fernández, Bernabeu-Wittel and García-Morillo5,Reference Croteau, Liang, Kozakewich and etal13}

Cardiac tumours are rare in newborns and are easily missed and or misdiagnosed. The child’s first echocardiographic examination in our hospital and the local hospital did not find a cardiac tumour. In this case, the difficulty of ultrasound scan was related to conventional echocardiographic section and their inability to show the tumour because it was located at the top of the atriums and ran along the posterior wall of the left atrium, extending to the coronary sinus and the bottom of the right ventricle, with a wide range and invasive growth. The conventional apical four-chamber cutting plane did not easily display the tumour. When the sound beam was tilted backward in an “unconventional” plane to show the coronary sinus (the posterior four-chamber of heart), the tumour located behind the heart could be shown. During the examination, the doctor only scaned conventional sections, focusing on the large pericardial effusion and cardiac function, thus not identifying tumour located behind the heart, resulting in a missed diagnosis. We now encourage our sonographers to pay attention to both routine standard section scanning and unconventional section scanning in their daily practice, especially in the setting of an unexplained pericardial effusion, as here. Cardiac kaposiform hemangioendothelioma occurs mainly in the pericardium, and it is rare to extend into the intracardiac cavity, although some can invade the myocardium. Echocardiography can be relied upon to show a solid tumour within a large pericardial effusion, whether located in the pericardial cavity or around the heart invading the pericardium, as well as pericardial thickening with nodular protrusion. However, this may be challenging if the tumour is diffuse, without a clear boundary with surrounding structures. If it is accompanied by the Kasabach–Merritt phenomenon, kaposiform hemangioendothelioma should be considered by ultrasonic examination.

The invasive and progressive growth of kaposiform hemangioendothelioma is different from that of typical infantile haemangioma, as the latter has a proliferative phase and then regresses. ^{Reference Goldenberg, Shiel and Subramanian14} Echocardiography of infantile haemangiomas shows that they are often localised and can be nodular; in contrast, kaposiform hemangioendotheliomas tend to infiltrate diffusely with ill-defined borders. The definite diagnosis depends on pathological examination.

Cardiac kaposiform hemangioendothelioma presents with severe symptoms and, once found, should be treated agressively. Surgical resection is the first choice, whilst for those that cannot be removed completely by surgery, vincristine combined with steroids has been effective. If conventional treatment is ineffective, one study reports successful tumour regression with sirolimus on a clinically refractory case. ^{Reference Kai, Wang and Yao15} When sirolimus is used, it is very important to use prophylactic antibiotics, monitoring drug levels regularly. In our case, because the tumour invaded the myocardium, complete operative removal was not possible, and the patient was treated with sirolimus for half a year. At present, good results had been achieved in short-term follow-up: the tumour has clearly shrunk in size, with coronary sinus diameter returning to normal, and the pericardial effusion disappeared (Fig. 3).

Figure 3. After 6 months, the tumour had significantly reduced in size (black arrow), the size of the coronary sinus had returned to normal (white arrow), and pericardial effusion had disappeared. LV = left ventricle; RA = right atrium; RV = right ventricle.