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The fine structure of hyaline inclusions (pseudopsammoma bodies) in meningiomas
Abstract:
"Hyaline inclusions" of a meningothelial meningioma were examined under the electron microscope. These eosinophilic, PAS-positive proteinaceous structures, which under the light microscope are seen in both extra- and intracellular location, were found by electron microscopy to consist of granular masses surrounded by cell membranes with microvilli. The "intracellular" bodies were also surrounded by similar microvilli in a space within the cells. Such spaces, variously known as intracellular ductules and "neolumen formation", have been previously described in mammary cancer, bronchiolar carcinoma and pleural mesotheliomas, among others, and have been, in the latter instances, regarded as signs of secretory differentiation. Thus, hyaline inclusions of meningiomas are different from truly intracellular hyaline bodies of neoplastic astrocytes (found by Rubinstein and Herman to be bodies within autophagic vacuoles) and may be regarded as a possible factor in ultrastructural differential diagnosis between meningiomas and gliomas.
Insights
Electron microscopy revealed that meningioma hyaline inclusions are extracellular structures, differing from intracellular bodies in neoplastic astrocytes. This finding aids in the ultrastructural diagnosis of meningiomas versus gliomas.
Area of Science:
- Neuropathology
- Electron Microscopy
- Cell Biology
Background:
- Hyaline inclusions in meningiomas appear eosinophilic and PAS-positive under light microscopy.
- These structures can be observed in both extracellular and intracellular locations.
Purpose of the Study:
- To characterize the ultrastructure of hyaline inclusions in meningiomas using electron microscopy.
- To differentiate meningioma hyaline inclusions from intracellular bodies found in neoplastic astrocytes.
Main Methods:
- Examination of meningioma tissue using electron microscopy.
- Analysis of the ultrastructural morphology of hyaline inclusions.
Main Results:
- Electron microscopy showed hyaline inclusions as granular masses surrounded by cell membranes with microvilli.
- The "intracellular" bodies were within spaces exhibiting microvilli, resembling intracellular ductules or neolumen formation.
- These findings contrast with truly intracellular hyaline bodies in neoplastic astrocytes, which are within autophagic vacuoles.
Conclusions:
- Meningioma hyaline inclusions are distinct from intracellular bodies in neoplastic astrocytes.
- The ultrastructure suggests these inclusions may represent a form of secretory differentiation.
- This distinction is valuable for the ultrastructural differential diagnosis between meningiomas and gliomas.
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