Rheumatic Granuloma

History of Discovery and Macroscopic-Microscopic Characteristics

Specific myocardial nodules were first discovered by the German pathologist L. Aschoff in 1904 (hence the historical term "Aschoff bodies"). Later, the detailed histogenesis of these lesions was described by V.T. Talalaev, giving the granuloma its dual eponym.

On macroscopic and microscopic examination, granulomas are round, oval, or spindle-shaped. Their sizes vary widely: from very small, submiliary (about 15–20 µm) to quite large (60×300 µm and more). The borders of the nodules are indistinct, and their extensions blend smoothly into the surrounding tissue. With standard hematoxylin and eosin (H&E) staining, cellular clusters and stromal changes are clearly visualized.

Cellular Composition and Structure

The rheumatic granuloma is characterized by a palisading or fan-like arrangement of cells around 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 prominent basophilic cytoplasm. Their nuclei are round or oval with a characteristic central condensation of chromatin. On histological cross-section, the nucleus resembles an "owl's eye," and on longitudinal section, a "caterpillar." It is important to remember that Anichkov cells are pathognomonic for rheumatic carditis.
• Aschoff giant 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 hypersensitivity reactions (Type I/III) are gradually replaced by delayed-type hypersensitivity (Type IV). In the initial (1st) stage, following the phase of serous-fibrinous inflammation, macrophages-histiocytes accumulate around the focus of fibrinoid necrosis and subsequently transform into large epithelioid cells.

Further evolution includes three stages:

1. "Flowering" (mature) granuloma. In this phase, macrophages are rich in RNA, contain glycogen granules, and actively secrete various cytokines. Microscopic preparations show a prominent cellular response.
2. "Waning" (resolving) 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.
3. "Scarring" (fibrotic) granuloma. Complete resorption of the fibrinoid and final sclerosis of the former granuloma site occur.

Topography (Body Localization)

Aschoff-Talalaev bodies most frequently affect the heart. In descending order of frequency, myocardial localization is distributed as follows:

1. Posterior wall of the left ventricle (LV).
2. Upper part of the interventricular septum.
3. Posterior wall of the right ventricle (RV).
4. Papillary muscles of the LV.
5. Anterior wall of the RV.
6. Anterior wall of the LV.
7. 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 bodies because Anichkov cells are completely absent in them.