A retrospective diagnosis of trauma-related self-resolving hemorrhagic skull lesions of Langerhans cell histiocytosis in a child through cytopathologic re-evaluation of a prior post-traumatic parotid gland hematoma.

The osteolytic skull lesions of Langerhans cell histiocytosis (LCH) in children are typically solid and slow-growing masses. A history of minor head trauma has been associated with the development and enlargement of LCH skull lesions in some children; head trauma has also rarely been associated with epidural hematoma from skull lesions of LCH. Isolated expansile cystic hemorrhagic skull lesions in LCH have been documented before in five cases, with two having a history of minor head trauma and one regressing spontaneously. Parotid gland involvement in LCH among children is rare, typically occurs as part of a disseminated multisystem disease, and is characterized by bilateral diffuse glandular enlargement. A unilateral parotid gland hematoma developing after minor trauma as the initial presentation of LCH has not been previously reported. Here, we describe a case of a 3-year-old boy with cystic hemorrhagic LCH lesions of the skull associated with minor head trauma. The skull lesions showed spontaneous regression before LCH was diagnosed through cytopathologic re-evaluation of a prior trauma-related unilateral parotid gland hematoma. A literature review of the imaging and clinical features of hemorrhagic skull lesions in LCH is presented.