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-M1 (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.