ROLE OF CYTOLOGY IN THE DIAGNOSIS OF LANGERHANS CELL HISTIOCYTOSIS IN PEDIATRIC BONE LESIONS

Kidada N. Gilbert-Lewis, M.D., O. Roncal, M.D., S. Qiu, M.D., Ph.D. and R. Nawgiri, M.D.

Departments of Cytopathology and Surgical Pathology, UTMB

Background: Langerhans cell histiocytosis is an uncommon disorder of the Langerhans cell, a subtype of dendritic antigen-presenting cells. It is a clonal proliferative disorder with an as yet unknown etiology and carries an approximately 10 percent overall mortality. It primarily affects the pediatric population; fifty percent of patients are younger than 10 years. It is a disease with a variable presentation, either localized or systemic, and any organ can be involved, but localized bone lesions are one of the most common manifestations. In spite of the lack of histological evidence of malignancy, this lesion behaves in a locally aggressive manner and often requires chemotherapy. Cytologic features are characteristic, and cytology preparations can be the primary diagnostic modality. Methods: Smears and imprints of two cases of Langerhans cell histiocytosis originating in the bone, (skull and femur) in children ages 5 and 4 years were studied. Histological documentation and immunohistochemical stain correlation were available. The initial radiological and clinical findings were concerning for malignancy. Results: Cytological smears from case 1 and touch imprints from case 2 were cellular with a polymorphous population of Langerhans histiocytes mixed with eosinophils, plasma cells, neutrophils and multinucleated giant cells. The Langerhans histiocytes were seen in loose clusters with indistinct cell borders andoval to reniform nuclei with delicate chromatin, many with prominent nuclear grooves. Cell cytoplasm was abundant. A cell block was made in case 1. Immunohistochemical stains for CD1-antigen and S-100 were done on the histological samples, which were strongly positive.