Atypical (Monomyelocytic) Myelogenous Leukemia

Abstract

Four cases of acute myelogenous leukemia characterized by peculiar leukemic cell populations are presented. The cytochemical, ultrastructural, biochemical, and functional features Electron microscopy observed in these leukemic cells suggested a similar pathological differentiation trend which apparently led to the combination in a single cell population of features characteristic of both monocytes and myelocytes or promyelocytes.

Acute Myelomonocytic Leukemia and the French-American-British Classification

“…Monocytic leukemia was diagnosed in 19 patients (mean age 47 years; 8 d and 11 [5,10]. Findings in the transitional myelomonocytic variant will now be described briefly and are indicated in table II.…”

“…To guarantee the unequiv ocal and reproducible subclassification of myeloid leukemias according to FAB clas sification, therefore, the application of peroxidase and of nonspecific esterase (with exposure to sodium fluoride) cyto chemistry should not only be recom mended, but ought to be obligatory. Cyto chemical reactions for esterase and for peroxidase may be performed parallel on different slides (as in our patients) or on the same slide using a double-staining method [10].…”

“…Indeed, for this purpose, a double-staining methode combining the demonstration of naphthol-AS-acetate esterase (for staining of monocytic cells) and of naphthol-AS-D-chloroacetate esterase (for staining of granulocyte precursors) on the same slide [ 10] would be desirable.…”

“…Most or nearly all of the leukemic cells in these pa tients show a morphology which renders the unequivocal diagnosis of either granu locytic or monocytic precursors rather dif ficult; and they are marked by an equally strong activity of both peroxidase and so dium fluoride-sensitive esterase. A normal counterpart of these leukemic cells is not observed in the bone marrow of healthy persons [5,10]. For delimitation from myelomonocytic leukemia, as defined above, this special subtype of M 4 leuke mia will be named 'transitional myelo monocytic variant' from now on.…”

The Application of Cytochemical Methods to the Study of Acute Leukemia

“…Based upon cytochemical features, an atypical kind of leukemia could be identified which showed a pattern of differentiation falling in between that of the typical monocytic and the typical promyelocytic patterns [51], Similar discrepancies w ere also observed in electro n m icroscopic an d in biochem ical investigations [23,51] giving further indications of the atypical maturation which we denoted 'myelomonocytoid' [51], Although other bone marrow cells do not contain organelles which may be unequivocally cytochemically characterized, they do show, when the appropriate cytochemical staining procedures are used, highly characteristic patterns, which may sometimes be distinctly altered in pathologic circum stances. For instance, in acute erythremias and erythroleukemias the leukemic erythroblasts exhibit very strong esterase splitting a-naphthyl-acetate for most part exceeding the enzyme activity observed in normal or otherwise pathological erythroblasts.…”