Specific skin manifestations in acute leukemia with monocytic differentiation a morphologic and immunohistochemical study of 11 cases

Background. Monocytic differentiation is present in the myelomonocytic (M4) and monocytic (M5) type of acute myeloblastic leukemia. Infiltration of the skin in acute myelomonocytic leukemia occurs in 10–20% of patients, the skin lesions occasionally being the first symptom, even preceding monocytosis. Methods. Eleven patients with myelomonocytic (n = 2) and monocytic leukemia (n = 9) were studied who had skin manifestations. Results and Conclusions. Clinically, all patients showed disseminated papules or nodules that corresponded histologically to nodular or diffuse infiltrates of monocytoid cells, occasionally displaying a whorled pattern. The currently available antibodies for paraffin‐embedded sections (lysozyme), elastase, leukocyte common antigen (CD45), MT1 (CD43), Leu‐Mi (CD15), LN2 (CD74), MB2, MB1 (CD45RA), LN1 (w75), Mac387, L26 (CD20), UCHL1 (CDR0), MT2 (CD45RA), and KP‐1 (CD68)) and chloracetate–esterase are not more helpful in diagnosis than are the histologic findings. By contrast, the antibodies used on frozen sections (Leu‐4 (CD3), Leu‐3a (CD4), BA1 (CD24), B4 (CD19), Leu‐M5 (CD11c), Vim12 (CD11b), VimD5 (CD15), KiM6 (CD68), KIM7 (CD68), My7 (CD13), and My9 (CD33) allow the definition of a reaction pattern that is diagnostic for acute myeloid leukemia with monocytic differentiation. Cancer 1993; 71:124‐32.