Monocytic leukemia. Clinically appearing as 'malignant reticulosis of the skin'.

Enzyme cytochemical (hydrolytic enzymes for cell differentiation), immunocytologic (B and T lymphocyte differentiation), and electron microscopic studies of skin infiltrates facilitate the proper diagnosis of myelomonocytic and lymphoreticular proliferations. With use of these methods, the original clinical diagnosis of malignant reticulosis of the skin was corrected to monocytic leukemia in a 65-year-old woman. Because primary involvement of the skin preceded monocytosis of the blood, it was concluded that the cutaneous infiltrates in our patient resulted from proliferation of tumor cells in the skin rather than from homing of the cells to, or settling of the cells in, the skin.