Electron microscope uses a microscope [called electron microscope] that uses electron beam to create specimen image. An electron microscope can create higher magnification and greater resolving power than a light microscope and enables to see much smaller objects in finer detail.
Examination of ultrastructural features of cellular and extracellular structures is a powerful diagnostic tool. The introduction of the transmission electron microscope in the early decades of the twentieth century dramatically expanded the investigative and diagnostic capabilities to study the submicroscopic details of diseased tissue including bone tumors and tumor like condition.
Types of Electron Microscopy
Transmission electron microscopy
Transmission electron microscopy is a microscopy technique in which a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through. An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor such as a CCD camera.
Scanning electron microscopy
A scanning electron microscope produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that can be detected and that contain information about the sample’s surface topography and composition. TSEM can achieve resolution better than 1 nanometer.
The scanning electron microscope provides an opportunity to examine the cell surface and intracytoplasmic membranous structures, as well as the three-dimensional composition of extracellular components. The so-called scanning and analytical instruments have little use in routine diagnosis.
The emergence of immunohistochemistry has significantly changed the approach to the diagnosis of bone tumors, and many diagnostic questions that in the past required ultrastructural studies are now addressed with the use of antibodies.
However, electron microscopy continues to provide unique, diagnostically useful information and should be used in addition to, not instead of, immunohistochemistry.
Diagnostically useful information can be obtained from cytologic preparations such as fine-needle aspirates. Limited ultrastructural studies can also be performed on tissue retrieved from paraffin-embedded material.
In bone tumors, as in general tumor pathology, ultrastructural studies provide valuable information about tumor histogenesis and differentiation pathways.
The most frequent applications of this technique in bone tumor pathology are in the differential diagnosis of:
1. Spindle-cell neoplasms
2. Small blue-cell neoplasms
3. Vascular versus nonvascular neoplasm
4. Metastatic tumors of bone.
Generally, tumors that cannot be diagnosed by light microscopy and that also have an inconclusive immunohistochemical profile very likely are not diagnosable by electron microsopcy.
Such studies have the best chance of being useful if conducted along with light microscopy and other applicable special techniques, with the formulation of specific questions that need to be answered.
The major limitations of ultrastructural studies in the diagnosis of bone tumors are
1. Only a small proportion of tissue can be sampled and examined.
2. Relatively few ultrastructural features are diagnostically specific.
3. It is occasionally difficult to distinguish neoplastic from nonneoplastic cells in ultrastructural studies.
Electron microscopy is informative if it is used by an individual experienced in surgical pathology who also examines the light microscopic sections and knows the specific differential diagnostic problems related to the case under investigation.
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