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Fibrinoid necrosis
Fibrinoid necrosis is a pathological lesion that affects blood vessels, and is characterized by the occurrence of endothelial damage, followed by leakage of plasma proteins, including fibrinogen, from the vessel lumen; these proteins infiltrate and deposit within the vessel walls, where fibrin polymerization subsequently ensues.
Although the term fibrinoid essentially means "fibrin-like", it has been confirmed through immunohistochemical analysis and electron microscopy that the areas referred to as "fibrin-like" do contain fibrin, whose predominant presence contributes to the bright, eosinophilic (pinkish) and structureless appearance of the affected vessels.
The earliest documented identification of fibrinoid changes dates back to 1880, when it was questioned whether these histological changes resulted from the deposition of a fibrinous exudate, or the degeneration and breakdown of collagen fibers.
The term fibrinoid was introduced to describe these changes, because distinguishing fibrinoid from hyaline deposits posed a significant challenge, as both exhibit a similar appearance under standard light microscopy. This morphological similarity necessitated the use of specialized histological staining techniques, such as phosphotungstic acid hematoxylin and various types of trichrome stains, to facilitate the distinction of fibrinoid material. Because these stains possess the ability to highlight and identify fibrin, this led to the term fibrinoid, which means "fibrin-like", being used to describe the affected vessels.
Nevertheless, as early as 1957, fibrin was indeed identified within fibrinoid, and by 1982, this understanding had advanced, with many researchers recognizing fibrinoid as a complex structure primarily composed of fibrin interwoven with various plasma proteins.
The term fibrinoid necrosis is, in fact, considered a misnomer, as the intense eosinophilic staining of the accumulated plasma proteins masks the true nature of the underlying changes in the blood vessel, and makes it virtually impossible to definitively determine whether the cells of the vessel wall are actually undergoing necrosis.
A 2000 review stated that "whether the lesion is truly necrotic, in the sense that it reflects the result of unprogrammed cell death, has never been investigated in depth", and an electron microscopy study examining fibrinoid necrosis in rat models with induced pulmonary hypertension found that fibrinoid changes weren't necessarily associated with necrosis of the smooth muscles of the media, and therefore recommended using the term fibrinoid vasculosis instead.
However, despite the inaccuracy, the microscopic characteristics of fibrinoid changes strongly resemble those of necrotic tissue, which is why the term fibrinoid necrosis continues to be used, even though it may not fully reflect the true underlying process.
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Fibrinoid necrosis
Fibrinoid necrosis is a pathological lesion that affects blood vessels, and is characterized by the occurrence of endothelial damage, followed by leakage of plasma proteins, including fibrinogen, from the vessel lumen; these proteins infiltrate and deposit within the vessel walls, where fibrin polymerization subsequently ensues.
Although the term fibrinoid essentially means "fibrin-like", it has been confirmed through immunohistochemical analysis and electron microscopy that the areas referred to as "fibrin-like" do contain fibrin, whose predominant presence contributes to the bright, eosinophilic (pinkish) and structureless appearance of the affected vessels.
The earliest documented identification of fibrinoid changes dates back to 1880, when it was questioned whether these histological changes resulted from the deposition of a fibrinous exudate, or the degeneration and breakdown of collagen fibers.
The term fibrinoid was introduced to describe these changes, because distinguishing fibrinoid from hyaline deposits posed a significant challenge, as both exhibit a similar appearance under standard light microscopy. This morphological similarity necessitated the use of specialized histological staining techniques, such as phosphotungstic acid hematoxylin and various types of trichrome stains, to facilitate the distinction of fibrinoid material. Because these stains possess the ability to highlight and identify fibrin, this led to the term fibrinoid, which means "fibrin-like", being used to describe the affected vessels.
Nevertheless, as early as 1957, fibrin was indeed identified within fibrinoid, and by 1982, this understanding had advanced, with many researchers recognizing fibrinoid as a complex structure primarily composed of fibrin interwoven with various plasma proteins.
The term fibrinoid necrosis is, in fact, considered a misnomer, as the intense eosinophilic staining of the accumulated plasma proteins masks the true nature of the underlying changes in the blood vessel, and makes it virtually impossible to definitively determine whether the cells of the vessel wall are actually undergoing necrosis.
A 2000 review stated that "whether the lesion is truly necrotic, in the sense that it reflects the result of unprogrammed cell death, has never been investigated in depth", and an electron microscopy study examining fibrinoid necrosis in rat models with induced pulmonary hypertension found that fibrinoid changes weren't necessarily associated with necrosis of the smooth muscles of the media, and therefore recommended using the term fibrinoid vasculosis instead.
However, despite the inaccuracy, the microscopic characteristics of fibrinoid changes strongly resemble those of necrotic tissue, which is why the term fibrinoid necrosis continues to be used, even though it may not fully reflect the true underlying process.