Langerhans Cell Histiocytosis of the Clavicle in a 13-Year-Old Boy

Langerhans Cell Histiocytosis (LCH) is a rare neoplasm characterized by abnormal proliferation of histiocytic cells. In this case report, we describe a unique case of a 13-year-old boy who presented to the clinic with an insidious onset of mid-clavicular pain. The provisional radiologic diagnosis of Langerhans Cell Histiocytosis of the clavicle was confirmed by an incisional biopsy of the left mid-clavicle lesion. The patient’s lesion was treated by curettage, bone grafting, and internal fixation, due to the presence of pathologic fracture. At the 2-year followup, the patient was asymptomatic, and the lesion showed complete resolution without recurrence. The case report highlights the characteristic features of Langerhans Cell Histiocytosis in an unusual location, the knowledge of which would help avoid delayed or missed diagnosis in the future. 1. Introduction Langerhans Cell Histiocytosis (LCH) is the current nomenclature for disorders previously known as histiocytosis X, which grouped eosinophilic granuloma, Hand-Schuller-Christian disease, and Letterer-Siwe disease [1–4]. LCH is an abnormal proliferation of tissue macrophages called Langerhans cells in one or more organs, including bone, skin, lymph nodes, lung, liver, spleen and bone marrow [1–4]. Patient age typically ranges from 5 to 15 years in about 90% of the cases, with a slight male predominance [1, 2]. The estimated incidence of LCH is 0.2–0.5 per 100,000 children per year in the USA. Majority (79%) of LCH are solitary lesions. The most frequent site of occurrence of LCH is the skull, followed by femur, jaw, pelvis, ribs, spine, scapula, humerus, and sternum [2]. Though rare, LCH of clavicle has been reported [5–8]. 2. Case Presentation A 13-year-old Caucasian male presented to clinic with an insidious onset of nondominant, left-sided, mid-clavicular pain for six weeks of duration. The mother described the texture of this area as “sand-like.” There was no history of trauma, fever, chills, night sweats, weight loss, joint pain, or swelling. On physical examination, the left clavicle demonstrated an isolated, tender, firm, nonerythematous, nonfluctuating, soft tissue swelling directly over the mid-clavicle without a noticeable deformity. Skin changes were absent. Laboratory examination showed total blood count of 8.9？K/UL (4.5–13.5) with normal differential. Erythrocyte sedimentation rate (ESR) was 14？mm/hour (0–10) and C-reactive protein (CRP) was 1.3？mg/dL (<1.0). Conventional radiograph of the left clavicle and a Tc-99m-MDP bone scan were performed. Subsequently CT scan and MRI were