EBM/11 reactivity in malignant histiocytosis.

A patient presented initially with a testicular mass, which on biopsy had morphological features consistent with malignant histiocytosis. The tumour cells labelled strongly with EBM/11, a murine monoclonal antibody with high specificity for cells of the human mononuclear phagocyte system. Subsequent clinical and laboratory studies confirmed the diagnosis. As poorly differentiated tumour cells reacted with EBM/11, this antibody may be useful in positively identifying malignant tumours with histiocytic differentiation from malignancies of other types where morphological detail alone is inconclusive in tumour classification.