Morel-Lavallee Syndrome: A Rare Tumefactive Lesion

First described by the French surgeon Maurice Morel-Lavallee in 1853, Morel-Lavallee syndrome (MLS) is a serolymphatic effusion resulting from tangential injury to richly vascularized tissues. The imaging characteristics may be variable over time due to lesion progression and the eventual organization of a fibrous capsule. We report a case of extensive MLS in the lower leg of a 12-year-old child. We discuss the ultrasound and magnetic resonance imaging findings and describe the differential diagnoses. LEARNING POINTS: The diagnosis of Morel-Lavallee syndrome is based on clinical examination and imaging techniques. The post-traumatic context is important for diagnosis. Morphological aspects depend on lesion progression and the eventual organization of a fibrous capsule.