Background and Objectives: Kaposiform hemangioendothelioma (KHE) and tufted angioma (TA) are rare vascular tumors in children historically associated with significant morbidity and mortality. This study was conducted to determine first line therapy in the absence of available prospective clinical trials. Methods: Patients from 17 institutions diagnosed with KHE/TA between 2005-2020 with > 6 months follow-up were included. Response rates to sirolimus and vincristine were compared at 3 and 6 months. Durability of response and response to other treatment modalities were also evaluated. Results: Of 159 unique KHE/TA subjects, Kasabach-Merritt phenomenon (KMP) was present in 64 (40.3%) and only 2 patients were deceased (1.3%). Over 60% (n=96) demonstrated treatment response at 3 months and >70% (n=114) by 6 months (no significant difference across groups). The vincristine group had higher radiologic response at 3 months compared to sirolimus (72.7% vs 20%, p=0.03) but there was no differences between these groups at 6 months. There were no differences in rates of recurrent or progressive disease between vincristine and sirolimus. Conclusions: In this large, multicenter cohort of 159 patients with KHE/TA, rates of KMP were consistent with historical literature but the mortality rate (1.3%) was much lower. Overall treatment response rates were high (>70%) and there were no significant difference in treatment response or durability of disease comparing sirolimus to vincristine. Our results support individualized treatment decision plans depending on clinical scenario and patient/physician preferences. Response criteria and response rates reported here will be useful for guiding future treatment protocols for vascular tumors.

Vascular anomalies are a group of disorders divided into two distinct subtypes: vascular tumors and vascular malformations. Vascular tumors are proliferative in nature, while malformations are non-proliferative. Simple, localized vascular malformations refer to a group of malformations that are localized to a single area of involvement. These simple malformations include capillary, lymphatic, venous, and arteriovenous malformations. The pediatric hematologist and oncologist is becoming increasingly involved in the diagnosis and management of these disorders. This review presents four cases as a means to discuss the diagnosis, clinical and imaging features, and management strategies of simple, localized vascular malformations.