Abstract / Summary
Abstract Background Osseous lesions in Langerhans cell histiocytosis (LCH) are radiologically nonspecific and may mimic infection, hematologic malignancies, or primary bone tumors, particularly when the spine or skull is involved. Here, we report two pediatric cases of osseous LCH in which multiparameter flow cytometry (MFC) of fresh lesional tissue provided ancillary diagnostic evidence. Case presentation Fresh lesional tissue obtained during surgery from two pediatric patients with clinically distinct forms of LCH was evaluated using MFC, histopathology and immunohistochemistry. In Case 1, a 12-year-old girl presented with newly diagnosed single-system multifocal bone LCH involving the cervicothoracic spine. MFC of the cervical vertebral lesion identified an abnormal population comprising 30.67% of the analyzed nucleated-cell events. In Case 2, a girl aged 3 years and 8 months, with recurrent multisystem LCH, presented with an active skull lesion. MFC identified an abnormal population comprising 16.09% of the analyzed nucleated-cell events in the skull lesion. IIn both cases, the abnormal cells expressed CD4, HLA-DR, CD1c/BDCA-1, CD1a and CD207 ,lacked CD3, CD14 and CD56; the population in Case 2 additionally showed dim CD123 expression. The CD1a⁺/CD207⁺/CD3⁻ immunophenotype supported the presence of abnormal Langerhans-like dendritic cells and was concordant with the histopathological and immunohistochemical findings. The first patient underwent surgery followed by vindesine- and prednisone-based treatment and remained stable without disease progression or recurrence during follow-up. The second patient underwent resection of the skull lesion and subsequently initiated MEK inhibitor therapy for recurrent disease, remaining clinically stable during short-term follow-up. Conclusions MFC of fresh osseous lesional tissue may help identify CD1a/CD207-coexpressing abnormal Langerhans-like dendritic cells and provide useful ancillary evidence for suspected or recurrent osseous LCH. Clinical trial number Not applicable.