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Proliferative myositis. An immunohistochemical and ultrastructural study
J N el-Jabbour1, M H Bennett, M M Burke
1Department of Histopathology, Mount Vernon Hospital, Northwood, Middlesex, England.
Insights
This study investigated proliferative myositis cells using advanced microscopy and antibody staining. Findings suggest these cells are myofibroblastic, potentially originating from pericytes.
Area of Science:
- Pathology
- Cell Biology
- Histogenesis
Background:
- Proliferative myositis is a rare benign lesion.
- The cellular origin of proliferative myositis remains debated.
- Understanding its cellular nature is crucial for accurate diagnosis.
Purpose of the Study:
- To elucidate the cellular composition of proliferative myositis.
- To determine the immunophenotype and ultrastructure of constituent cells.
- To discuss the implications for the histogenesis of this condition.
Main Methods:
- Immunohistochemical analysis using a panel of 12 antibodies (avidin-biotin-peroxidase complex technique).
- Ultrastructural examination by electron microscopy.
- Analysis of four cases of proliferative myositis.
Main Results:
- Both giant ganglion-like cells and spindle cells exhibited positive cytoplasmic staining for vimentin, actin (C4), and alpha-smooth muscle actin-1.
- Desmin staining was positive in only one case.
- Electron microscopy revealed features consistent with myofibroblasts, including thin filaments and dense bodies.
Conclusions:
- The study implies a myofibroblastic nature for the cells in proliferative myositis.
- Findings support the hypothesis that these cells are derived from pericytes.
- This clarifies the histogenesis and cellular identity of proliferative myositis.
Abstract:
We studied four cases of proliferative myositis by the avidin-biotin-peroxidase complex technique, using a panel of 12 antibodies, and by electron microscopy. The aim was to clarify the nature of their constituent cells, specifically the giant ganglion-like cells and spindle cells, and to discuss the implications for histogenesis. In all cases, both cell types showed positive cytoplasmic staining with antibodies to vimentin, actin (C4), and alpha-smooth muscle actin-1, but in only one was there positive staining with desmin. No staining was obtained with factor XIIIa, muramidase, alpha-1-antitrypsin, myoglobin, S-100 protein, CAM 5.2, factor VIII-related antigen, or neuron-specific enolase. By electron microscopy, both types of cells were seen to contain numerous thin filaments, dense bodies, coated and pinocytotic vesicles, active and dilated rough endoplasmic reticulum, few microvilli, and incomplete desmosomal junctions. Our findings imply a myofibroblastic nature for the giant ganglion-like cells and spindle cells. Our observations also support the hypothesis that they are derived from a pericytic cell.