Extracranial skeletal Langerhans cell histiocytosis: MR imaging features according to the radiologic evolutional phases

PurposeThe purpose was to describe the magnetic resonance (MR) findings of extracranial skeletal Langerhans cell histiocytosis according to the radiologic evolutional phases.Materials and methodsTwenty-two patients with pathologically confirmed extracranial skeletal Langerhans cell histiocytosis were included. The lesions were classified as early, mid, and late phases according to the radiologic evolutional phases. MR images were retrospectively analyzed regarding signal intensity, internal hypointense band, fluid levels, periosteal reaction, adjacent bone marrow and soft tissue abnormal signal, and patterns of contrast enhancement in each phase.ResultsAccording to the radiologic evolutional phases, there were 4 patients with early phase, 16 with mid phase, and 2 with late phase. All cases showed hypointense to intermediate signal intensity on T1-weighted images. On T2-weighted images, 12 (55%) of the 22 lesions were hyperintense, and 10 (45%) showed intermediate signal. All lesions showed diffusely heterogeneous signal on T2-weighted images. Internal low-signal bands of the lesions were observed in 13 cases (59%). There were two cases with fluid levels in mid phase. Periosteal reaction was observed in 13 (59%) cases. Adjacent bone marrow or soft tissue abnormal signal was observed in 20 cases (91%), respectively. According to early, mid, and late phases, bone marrow and soft tissue abnormal signals were observed in 100%, 100%, and 0% cases, respectively. Soft tissue mass was seen in eight cases (36%). Ten (46%) lesions showed cortical destruction, including one patient with a pathologic fracture. Among 21 patients with contrast infusion, diffuse enhancement was observed in 19 patients (90%), and marginal and septal enhancement was seen in 2 patients (10%).ConclusionMR imaging was helpful in the diagnosis of extracranial skeletal Langerhans cell histiocytosis, particularly in early and mid phases.