Langerhans' cells histiocytosis is a disease that belongs to the group of histiocytic disorders and is considered a rare pathology. It results from a proliferation and accumulation of cells of the phagocytic mononuclear system, including Langerhans' cells. This paper reports a case of a 4-year-old patient who presented a growing, swollen, nodular, depressible and mobile lesion in the right retroauricular region, without pain or phlogistic signs for 6 months, besides erosive and necrotic lesions in the first and second right molars. The confirmatory diagnosis was made by biopsy and immunohistochemistry. This is a study of the medical record, histological evaluations, laboratory and imaging tests of the patient, with the aim of discussing the pathology, making the diagnosis and treatment earlier.