Clinical and pathologic cutaneous manifestations of malignant histiocytosis

The clinical and pathologic changes in the skin of five patients with malignant histiocytosis were studied. The clinical signs included papules, nodules, noduloulcers and purpura. The histopathologic changes included exocytosis of inflammatory cells, infiltration of the papillary and reticular dermis with neoplastic histiocytes, and periadnexal and perivascular infiltrates. Phagocytosis of RBCs and nuclear debris by atypical histiocytes was seen in two cases. In one case, the skin lesions were the only initial manifestation of the disease. Skin involvement occurs in about 10% to 15% of all cases of malignant histiocytosis. Hence, it is important to include malignant histiocytosis in the differential diagnosis of patients with such skin lesions, especially when clinical symptoms may be suggestive of this disease.