Kaposiform Hemangioen dothelioma (KHE) is an uncommon vascular tumor predominantly seen in infants. Cohort studies [13] have shown that 52.1% of KHE cases are identified at birth, and 91.8% manifest within the first year of life. In our study, 90.91% (120/132) of the children were diagnosed within their first year, aligning closely with previous findings. The International Society for the Study of Vascular (ISSVA) Anomalies categorizes KHE based on its growth characteristics as a tumor with “locally aggressive or borderline behavior.” In our study, 125 KHE cases presented as single lesions, with 7 cases exhibiting multiple lesions. Although there have been no reports of distant metastasis internationally, instances of multifocal KHE distribution [14] have been documented, mirroring the outcomes of this study.

Among pediatric vascular-origin diseases, KHE is relatively rare, and its nuances are often not well-understood by clinical pediatricians. However, KHE can lead to Kasabach-Merritt Phenomenon (KMP), resulting in severe clinical implications, underscoring the importance of early detection. The majority of affected children in this study showed cutaneous involvement, with extensive purple-red (56 cases) or red (55 cases) firm, warm nodules, distinctly different from common hemangiomas. These characteristics, combined with imaging features, facilitate a preliminary diagnosis. A minority of patients without skin involvement (21 cases) presented with firm, immobile subcutaneous nodules, which could be misidentified as other types of hemangiomas [15]. Given KHE’s rapid progression and local aggressiveness, especially in cases associated with KMP where bleeding is a possibility, biopsies should be approached with caution.

KMP is a clinical hallmark of KHE, characterized by decreased platelet count, reduced fibrinogen levels, elevated D-dimer levels, and a hypocoagulable state potentially leading to intermittent bleeding [16]. The incidence of KMP correlates positively with the tumor’s diameter. KHEs located in muscles, joints, or bones are less likely to trigger KMP due to limited growth space, which inhibits abnormal proliferation of vascular endothelial cells [17]. Other symptoms depend on the KHE’s location; bone involvement can lead to destruction and, in severe cases, pathological fractures, limiting limb movement and causing pain. If the pleura or pericardium is involved, pleural or pericardial effusion may occur; KHEs in the abdominal cavity or retroperitoneum can lead to secondary intestinal obstruction or hydronephrosis, and pancreatic KHEs may cause obstructive jaundice.

Ultrasound imaging of KHE reveals heterogeneous echoic masses within soft tissue, generally larger, irregular in shape, and poorly defined due to its invasive growth characteristics. The lesion’s center appears hypoechoic, with surrounding tissue often thickened and echo-enhanced due to tumor infiltration [18], presenting a distinctive feature. Few lesions may contain tubular anechoic areas internally. Color Doppler ultrasound demonstrates abundant blood flow within the lesion, classified as Adler grade III, displaying a characteristic branching pattern from deep to superficial layers. This study observed that the proportion of lesions extending into the fat layer and invading the muscle was lower in the KHE group compared to the KMP group, with smaller lesion diameters in the KHE group. The primary blood flow classification in the KHE group was grade II (45.21%), followed by grade III (45.10%), whereas in the KMP group, grade III was predominant (93.22%). Research by Liu et al. [19] also indicated that larger lesions, particularly those in KHE with KMP, suggest a higher likelihood of invading surrounding tissues or accompanying KMP, aligning with our findings and highlighting the need for close monitoring of platelet fluctuations in KHE patients.

KHE is invasive, with both focal and diffuse lesions on MRI appearing as irregular soft tissue masses with ragged edges, capable of invading surrounding fat, superficial fascia, deep fascia, muscle, and even bone [20]. All lesions in the children included in this study showed invasive characteristics, consistent with research conclusions. Furthermore, 63.01% of lesions in the KHE group invaded the muscle layer, compared to 79.66% in the KMP group, indicating a significantly lower rate in the KHE group. Contrast-enhanced MRI of KHE typically shows significant, persistent enhancement of the lesion, surrounded by abundant vasculature. In this study, the incidence of flow voids in the KHE group was lower than in the KMP group, likely related to the pathological features of the tumor’s vascular channels and thin-walled lymphatic vessels [21].

This study has limitations, including the similar age range of the cases, which does not provide direct evidence for the consistency of KHE imaging features across different age groups. The sample selection did not include cases in rare locations. Demonstrating consistent ultrasound and MRI characteristics of KHE across different age groups and rare locations could further enhance the clinical application value of ultrasound diagnosis for KHE.