Background: The authors report the immunohistochemical, ultrastructural, and cytogenetic findings in a case of malignant histiocytic proliferation in an infant.
Procedure: The patient presented initially with bone lesions without skin or systemic involvement. Multiple biopsies were studied extensively by immunohistochemistry and electron microscopy. Cytogenetic studies of cell cultures supplemented with granulocyte-monocyte colony stimulating factor (GM-CSF) were also performed.
Results: Morphologically, the cells resembled Langerhans cells, although with greater pleomorphism, as evinced by cells with usual polylobated nuclei. These cells expressed markers for macrophages and antigen presenting cells and were CD1a- and S-100-positive, but lacked Birbeck granules. The cells grown in culture supplemented with GM-CSF showed a unique combination of numerical and structural abnormalities affecting chromosomes 1, 6, 8, and 10. The disease followed a malignant course leading to the patient's demise despite aggressive chemotherapy and bone marrow transplant.
Conclusions: The findings suggest a malignant hematopoietic stem-cell neoplasm with a capacity for macrophage or dendritic-cell differentiation. Morphology and immunophenotypic features place this neoplasm within the group recently conceptualized as indeterminate-cell histiocytosis.