Histological review of referred malignant histiocytoses. Left: liver infiltration by MH, secondary to a large B-cell lymphoma. Tumoral cells only had a weak cytoplasmic staining with CD163 but had a strong nuclear positivity with PU.1. Right: mass involving adrenal glands referred as histiocytic sarcoma. Massive infiltration by reactive DCs with strong CD163 expression, and it was difficult to see that tumor cells were negative. This contrasts with obvious negativity of tumor cells with PU.1. All pictures (original magnification ×300). DC, dendritic cell; H&E, hematoxylin and eosin.