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Ultrastructural characteristics and lysozyme content in hypergranular and variant type of acute promyelocytic
D Shaft1, M Shtalrid, A Berebi
1Efrati Research Institute for Blood Cells and Cytology, Rehovot, Israel.
Abstract:
We investigated the electronmicroscopic (EM) features and cellular lysozyme (LZ) content in 16 cases of acute promyelocytic leukaemia (APL): 11 cases of the hypergranular form (M3) and five cases of the microgranular variant (M3-V). The main EM features in all cases were: irregular, folded or bilobed nuclei, many cytoplasmic granules, distended rough endoplasmic reticulum (RER) cisternae which, in some cases, presented as stellate forms (more frequent in M3-V), and bundles of cytoplasmic microfilaments. Many Auer rods were present in M3 cases and few in M3-V; most of these disclosed parallel tubular arrays (PTA) with a varied periodicity ranging from 13 to 26 nm. There was a significant difference between M3 and M3-V (P<0.0001) in both the number of granules per cell section (62.9 +/- 34.5 v 38.0 +/- 23.6) and in the granule section area (0.044 +/- 0.033 v 0.026 +/- 0.015 microm2). In some cases, mainly in M3-V, we found cells with large granules containing PTA which probably represent poorly developed Auer rods. Intracellular LZ content assayed by a post-embedding immunogold method, showed high granular LZ density (in the range of that found in M4 and M5) in M3 cells and very low granular LZ content in M3-V. This study adds new objective parameters for the diagnosis of these two types of APL and provides new information on their LZ pattern of expression.
Insights
Electron microscopy and lysozyme content distinguish hypergranular acute promyelocytic leukemia (APL M3) from its microgranular variant (M3-V). These objective parameters aid in diagnosing APL subtypes.
Area of Science:
- Hematology
- Oncology
- Cell Biology
Background:
- Acute promyelocytic leukemia (APL) has distinct subtypes, hypergranular (M3) and microgranular (M3-V).
- Distinguishing between these subtypes is crucial for accurate diagnosis and treatment.
- Electron microscopy (EM) and cellular content analysis offer potential objective diagnostic markers.
Purpose of the Study:
- To investigate and compare the electron microscopic (EM) features and cellular lysozyme (LZ) content in hypergranular APL (M3) and its microgranular variant (M3-V).
- To identify objective parameters that can differentiate between M3 and M3-V.
- To provide new insights into the lysozyme expression patterns in APL subtypes.
Main Methods:
- Electron microscopy (EM) was used to examine cellular morphology in 16 APL cases (11 M3, 5 M3-V).
- Cellular lysozyme (LZ) content was quantified using a post-embedding immunogold method.
- Statistical analysis was performed to compare features between M3 and M3-V.
Main Results:
- Significant differences in nuclear shape, cytoplasmic granule count, granule size, and Auer rod presence were observed between M3 and M3-V.
- M3 cases showed abundant granules and Auer rods with parallel tubular arrays (PTA), while M3-V had fewer granules and less frequent Auer rods.
- M3 cells exhibited high granular lysozyme density, whereas M3-V cells showed very low granular lysozyme content.
Conclusions:
- Electron microscopy and lysozyme content analysis provide objective parameters for differentiating between hypergranular APL (M3) and microgranular APL (M3-V).
- These findings enhance diagnostic capabilities for APL subtypes.
- The study contributes novel information regarding the lysozyme expression profile in distinct APL variants.