Prenatal Diagnosis and Management of Kaposiform Hemangioendothelioma With Kasabach–Merritt Phenomenon: Imaging Features and First Experience With Maternal Sirolimus Therapy

Objective To describe the prenatal diagnosis, evolution, and perinatal management of kaposiform hemangioendothelioma (KHE) complicated by the Kasabach–Merritt phenomenon (KMP), and to report the first documented use of maternal sirolimus therapy (MST) in this setting. Methods We retrospectively reviewed four fetuses with a prenatal soft‐tissue mass suspected for KHE. Imaging characteristics, fetal complications, perinatal outcomes, and postnatal hematologic data were analyzed. MST was initiated in one severe case with rapidly progressive disease and early fetal compromise. Results All lesions demonstrated infiltrative margins, marked hypervascularity, and T2‐hyperintense signal on MRI. Three fetuses showed prenatal signs suggestive of evolving KMP. Two pregnancies were terminated. Among the two liveborn infants, one developed early neonatal KMP requiring urgent sirolimus therapy. All lesions demonstrated infiltrative margins, marked hypervascularity, and T2‐hyperintense signal on MRI. Three fetuses showed prenatal signs suggestive of evolving KMP. Two pregnancies were terminated. Among the two liveborn infants, one developed early neonatal KMP requiring urgent sirolimus therapy. In the most recent case, a temporal association was observed between MST initiation and early reduction of tumor infiltration on follow‐up MRI. The infant was delivered at 39 weeks and responded to combined sirolimus–steroid therapy. Conclusion Prenatal imaging can strongly suggest KHE and identify early signs of KMP. This series provides preliminary evidence that MST may represent a promising antenatal therapeutic option in selected severe cases.