History of Discovery and Macro-Microscopic Characteristics
Specific nodules in the myocardium were first discovered by the German pathologist L. Aschoff in 1904 (hence the historical name "Aschoff bodies"). Later, the detailed histogenesis of these structures was described by the Russian scientist V.T. Talalaev, giving the granuloma a dual eponym.
Upon macro- and microscopic examination, granulomas are round, oval, or spindle-shaped. Their size varies widely: from very small, submiliar (about 15–20 µm) to quite large (60×300 µm or more). The borders of the nodules are indistinct, with their processes smoothly blending into the surrounding tissue. With standard hematoxylin and eosin staining, cellular clusters and stromal changes are clearly visualized.
Cellular Composition and Structure
The rheumatic granuloma is characterized by a palisade or fan-like arrangement of cells around the central masses of fibrinoid. T-lymphocytes, B-lymphocytes, and plasma cells take an active part in the development of the inflammatory focus.
Two special types of cells give the nodule its specificity:
- Anichkov cells. These are large epithelioid cells with pronounced basophilic cytoplasm. Their nuclei are round or oval with a characteristic central arrangement of chromatin. On a histological section, the nucleus looks different: in cross-section it resembles an "owl's eye," and in longitudinal section, a "caterpillar." It is important to remember that Anichkov cells are absolutely pathognomonic for rheumatic carditis.
- Aschoff cells. These are multinucleated giant histiocytes involved in phagocytosis.
Stages of Formation and Evolution
The life cycle of the granuloma is closely linked to immune processes: immediate-type hypersensitivity (ITH) reactions are gradually replaced by delayed-type hypersensitivity (DTH) reactions. In the initial (1st) stage, following the phase of serous-fibrinous inflammation, macrophage-histiocytes accumulate around the focus of fibrinoid necrosis, subsequently transforming into large epithelioid cells.
Further evolution includes three stages:
- "Flowering" (mature) granuloma. In this phase, macrophages are rich in RNA, contain clumps of glycogen, and actively secrete various cytokines. Microscopic preparations show a prominent cellular response.
- "Fading" granuloma. Characterized by the appearance of fibroblasts. The amount of fibrinoid detritus begins to decrease noticeably, accompanied by lymphoid infiltration and initial sclerosis of the myocardial stroma.
- "Scarring" granuloma. Complete resorption of the fibrinoid and final sclerosis of the former granuloma area take place.
Topography (Body Localization)
Aschoff-Talalaev nodules most frequently affect the heart. In order of decreasing frequency, their localization in the myocardium is distributed as follows:
- Posterior wall of the left ventricle (LV).
- Upper part of the interventricular septum.
- Posterior wall of the right ventricle (RV).
- Papillary muscles of the LV.
- Anterior wall of the RV.
- Anterior wall of the LV.
- Apex of the heart.
Extracardiac localization includes joint capsules, aponeuroses, peritonsillar connective tissue, and the stroma of other organs. However, extracardiac granulomas do not have the typical appearance of Aschoff-Talalaev nodules, as they completely lack Anichkov cells.
Briefly: answers to topical questions
What biochemical and structural components make up the masses of fibrinoid necrosis in the center of the nodule?
Fibrinoid necrosis masses consist of a complex substance—fibrinoid, which forms as a result of profound connective tissue disorganization. Its composition includes the following components:
- Proteins and polysaccharides — breakdown products of collagen fibers and ground substance.
- Blood plasma proteins — infiltrate the tissue due to increased vascular permeability (primarily fibrinogen, which converts into fibrin).
- Nucleoproteins — elements of destroyed connective tissue cells.
- Fibrin — an obligatory structural component delivered with blood plasma.
To remember the appearance of the Anichkov cell nucleus in sections, imagine an owl hunting a caterpillar. If you cut the nucleus crosswise, an "owl's eye" looks back at you; if lengthwise, a "caterpillar" is crawling.
Class and exam questions
Who first described rheumatic granulomas, and when?
Nodules in the myocardium were first discovered by L. Aschoff in 1904. Later, their histogenesis was described in detail by V.T. Talalayev, which is why the dual eponym is established in the literature.
What is the main function of the rheumatic granuloma?
Its main task is the phagocytosis of necrotic masses and immune complex remnants formed as a result of fibrinoid necrosis of vessels and connective tissue.
How do extracardiac rheumatic granulomas differ from those in the myocardium?
In extracardiac granulomas (e.g., in joint capsules or aponeuroses), Anichkov cells are never found, which is why they lack the typical structure of Aschoff-Talalaev nodules.
What else to study on this topic
- Mechanisms of microcirculatory fibrinoid necrosis development
- The role of T- and B-lymphocytes in granuloma formation
- The shift of hypersensitivity reactions (ITH to DTH) in the dynamics of inflammation
- Morphological differences between Aschoff cells and other multinucleated giant cells
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