Dendritic cell phenotype in localized malignant histiocytosis of the small intestine.

We studied a unique case of a localized non-Hodgkin's lymphoma of the pleomorphic large-cell type arising in the small intestine to determine its phenotype. Immunohistochemical staining for S100 protein, lysozyme, alpha 1-antitrypsin, and Leu-M1 was performed. Many lymphoma cells were positive for S100 protein and were negative with the other antibodies. These findings indicate a probable dendritic cell origin for this lymphoma similar to that seen in histiocytosis X and some cases of malignant histiocytosis, but apparently quite distinct from the S100 protein-negative, lysozyme-positive, alpha 1-antitrypsin-positive cells seen within the mononuclear phagocytic system.