Eight cases of Philadelphia chromosome positive chronic myelogenous leukemia (CML) in blast crisis have been studied by ultrastructural per-oxidase cytochemistry. In 7 cases, peroxidase reaction product was seen in the nuclear envelope and rough endoplasmic reticulum (RER) of the blasts. These cells had no cytoplasmic granules. In 6 cases, a few cells also showed peroxidase reaction product in the nuclear envelope, RER, and all cytoplasmic granules.
In contrast, peroxidase reaction product was not shown in the nuclear envelope and RER in all blasts in one case. The blasts did not have granules. Although these cells could not be identified, the high level of terminal deoxy-nucleotidyl transferase (TdT) activity suggested this case had undergone ‘lymphoid’ crisis.
Ultrastructural peroxidase cytochemistry is, therefore, useful for the identification of blast cells in CML-blast crisis.
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