Acute promyelocytic leukemia toluidine blue subtype

Area of Science:

• Hematology
• Oncology
• Cell Biology

Background:

• Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia.
• A rare hypergranular variant of APL with basophilic granules has been recognized.
• The biological and clinical significance of this subtype requires further investigation.

Purpose of the Study:

• To determine the incidence of the basophilic granular subvariant of APL.
• To evaluate the biological and clinical significance of this APL subtype.
• To identify diagnostic markers differentiating this subtype from other leukemias.

Main Methods:

• Morphological, cytochemical, immunological, and cytogenetic analyses were performed on 53 untreated APL patients.
• Toluidine blue staining was used to identify metachromatic granules.
• Peroxidase and esterase activities were assessed, alongside ultrastructural examination.

Main Results:

• 19% of APL cases (10 out of 53) exhibited metachromatic basophilic granules.
• This subtype showed weaker peroxidase positivity and usually present esterase activities.
• Immunophenotypic and cytogenetic profiles did not significantly differ from other APL subtypes.
• Coagulopathy was severe, and median survival was short, despite low white cell counts.

Conclusions:

• The basophilic granular subvariant of APL occurs in 19% of cases and has distinct morphological and cytochemical characteristics.
• While immunophenotypic and cytogenetic features are similar to classic APL, clinical outcomes can be severe.
• Cytochemical, immunologic, and cytogenetic findings are crucial for differentiating this APL subtype from M2 leukemia and mast cell leukemia.