Dystrophies: parenchymal, stromal-vascular, and mixed
Granular dystrophy of the renal tubular epithelium is characterized by an increase in the volume of the convoluted tubular epithelium, eosinophilic cytoplasmic granularity, and indistinct nuclear contours. Fatty liver dystrophy ("goose liver") manifests as vacuoles of various sizes filled with fat; staining with Sudan III turns the droplets orange, which allows differentiation between fatty and hydropic dystrophies.
Among stromal-vascular dystrophies, mucoid swelling of the heart valve in rheumatism (staining with toluidine blue produces the metachromatic phenomenon — purple staining of the focus) and hyalinosis of the splenic capsule with its marked thickening and homogenization are distinguished. Sago spleen shows amyloid exclusively in the follicles of the white pulp around the central arterioles; lardaceous spleen shows diffuse amyloid deposition. In liver amyloidosis, amyloid masses are located between the cords, and hepatocytes undergo atrophy.
Mixed dystrophies: pulmonary hemosiderosis (Prussian blue stain — cells with dark brown hemosiderin), malarial pigmentation of the spleen with grains of hemozoin, pulmonary anthracosis with coal dust particles in the interalveolar septa.
Necrosis and circulatory disorders
Waxy necrosis of the rectus abdominis muscle: loss of cross-striation, absence of nuclei, fiber fragmentation. Caseous necrosis of a lymph node in tuberculosis is surrounded by a palisade of epithelioid cells, lymphocytes, and Langhans giant cells. Ischemic renal infarct is a necrotic area in the cortical layer with preserved tubular contours but lacking nuclei.
Nutmeg liver: congestion of the central parts of the lobules with blood, necrosis and atrophy of central hepatocytes, fatty dystrophy at the periphery. Pulmonary edema — alveoli are filled with a homogeneous pink mass. Red thrombus contains fibrin threads and formed elements with a predominance of erythrocytes. Hemorrhagic pulmonary infarct — alveoli are completely filled with erythrocytes. Fat embolism of pulmonary vessels is detected by lipid droplets in the capillaries when stained with Sudan III.
Inflammation
Catarrhal colitis: hyperemia, edema, leukocytic infiltration, hypersecretion of mucus. Diphtheritic colitis — a fibrinous film penetrating the entire thickness of the mucosa with microbial colonies. Purulent nephritis: microbial emboli in the glomeruli, foci of necrosis, formation of abscesses. Fibrinous pleuritis — a layer of fibrin with leukocytes on the visceral pleura.
Productive specific inflammation: epithelioid cell tubercles in the lungs with caseous necrosis, epithelioid cells, and Langhans cells. Syphilitic mesaortitis — an infiltrate of lymphoid and plasma cells around the vasa vasorum followed by collostolysis. Granulation tissue contains small vessels, histiocytes, fibroblasts, lymphocytes, plasmacytes, and erythrocytes.
Compensatory-adaptive processes and atrophy
Bone callus at the fracture site: fibrous connective tissue with elongated cells and newly formed vessels. Secondary intention wound healing proceeds through granulation tissue with a zone of vertical vessels. Organized thrombus in an artery (van Gieson stain): protein masses, collagen fibers, elastic fibers with recanalization.
Thymic atrophy: adipose tissue with lymphoepithelial islands and Hassall's corpuscles. Pulmonary emphysema — large air cavities with thinned walls. Brown atrophy of the liver: reduction of lobules and hepatocytes, accumulation of lipofuscin. Myocardial hypertrophy — enlargement of fibers and hyperchromic nuclei. Glandular hyperplasia of the endometrium with cystically dilated glands.
Tumors
Skin papilloma: papillary growths of stratified squamous epithelium without atypia, preserving polarity and basal orientation. Squamous cell keratinizing carcinoma of the esophagus — atypical strands with cancer pearls. Fibroadenoma of the breast exists in intracanalicular and pericanalicular forms.
Gastric adenocarcinoma: bizarre glandular structures with loss of polarity. Medullary carcinoma — predominance of parenchyma, solid carcinoma — equal ratio of parenchyma and stroma, scirrhus — predominance of stroma. Fibrosarcoma: atypical fibroblasts predominate over collagen. Skin melanoma — pleomorphic cells containing melanin pigment.
Cardiovascular diseases and rheumatic diseases
Aortic atherosclerosis: destruction of the basement membrane and fibers, intimal infiltration by lipids (Sudan III staining reveals red lipids). Aortic calcification — blue deposits of calcium salts in atheromatous masses. Hyalinosis of renal arterioles — hyaline in the subendothelial space.
Myocardial infarction — necrosis with absence of cardiomyocyte nuclei, demarcation inflammation, contraction bands. Organizing infarct is represented by granulation tissue; the outcome is small-focal cardiosclerosis (with van Gieson stain, connective tissue layers are red, cardiomyocytes are green).
Recurrent verrucous endocarditis: club-shaped valve thickening, fibrinoid necrosis, organizing vegetations. Rheumatic myocarditis — granulomas of macrophages around foci of fibrinoid necrosis.
Diseases of internal organs and infections
Blood diseases: in chronic myeloid leukemia, the liver is infiltrated by myelocytes along the sinusoids; in chronic lymphocytic leukemia, by lymphocytes in the portal tracts. In Hodgkin's lymphoma, Reed–Sternberg cells are characteristic.
Gastrointestinal tract: chronic gastric ulcer in exacerbation contains a fibrinoid-leukocytic layer, fibrinoid necrosis, and granulation tissue. Phlegmonous appendicitis — diffuse neutrophilic infiltration of all layers. Portal cirrhosis: connective tissue septa with pseudo-lobules; biliary cirrhosis — tissue proliferation along the bile ducts.
Kidneys: acute and chronic pyelonephritis (thyroid kidney), subacute extracapillary glomerulonephritis with crescents, amyloid nephrosis (Congo red stain). Lungs: lobar pneumonia in the stage of gray hepatization, carnification, bronchopneumonia, primary tuberculous focus (Ghon) and miliary tuberculosis with caseous necrosis and Pirogov–Langhans cells. Infections: medulloid swelling of Peyer's patches in typhoid fever with typhoid granulomas, small intestine in cholera with "bald" villi.
Key points
- Dystrophies are diagnosed by characteristic cytoplasmic inclusions: fat, hemosiderin, amyloid, lipofuscin, using special stains.
- The hallmark of necrosis in any localization is the absence of cell nuclei and the loss of tissue architecture.
- The tuberculous granuloma contains caseous necrosis, epithelioid cells, and Pirogov–Langhans giant cells.
- Fibrinous inflammation is divided into croupous and diphtheritic depending on the depth of the lesion.
- The morphology of gastric cancer depends on the ratio of parenchyma to stroma: medullary, solid, scirrhous.
- Myocardial infarction goes through stages of necrosis, demarcation inflammation, and organization, resulting in cardiosclerosis.
- Liver cirrhosis is characterized by pseudolobules and depends on the localization of fibrosis (portal, biliary).
- Specific marker cells: Pirogov–Langhans cells in tuberculosis, Reed–Sternberg cells in Hodgkin's lymphoma.