Painless Scalp Swellings Unmasking Multifocal Langerhans Cell Histiocytosis in a Child

A bstract Langerhans cell histiocytosis (LCH) is a rare pediatric disorder with heterogeneous clinical manifestations, frequently involving the skeletal system. Here, we report a case of a young girl presenting with multiple painless, progressively enlarging scalp swellings, initially suggestive of a benign etiology. Imaging revealed a large osteolytic calvarial defect along with an additional lytic lesion involving the left ninth rib, raising suspicion of multifocal LCH. Considering the high risk of hemorrhage associated with scalp biopsy, a rib lesion biopsy was performed, which confirmed the diagnosis on histopathology and immunohistochemistry (CD1a and S-100 positivity). The patient was treated with systemic chemotherapy using vinblastine and corticosteroids with a favorable early response. This case report highlights the importance of considering LCH in the differential diagnosis of atypical scalp swellings in children and emphasizes the role of judicious biopsy site selection to minimize procedural risk while ensuring diagnostic accuracy.