Chapter 3 - Infection & Inflammation Flashcards
What are the features of acute inflammation?
Vascular congestion, edema
Fibrinous exudate, tissue damage & necrosis
Neutrophils
What can trigger acute inflammation?
How can it resolve?
Trauma, ischemia, toxins, infection…
Can be followed by resolution, fibrosis/scar, abscess formation, or chronic inflammatory change
Describe the appearance of granulation tissue
Watery or myxoid background with inflammatory cells, sparse fibroblasts, and capillaries with prominent endothelium.
Describe the appearance of biopsy site changes
Fibroblast proliferation (early scar)
Foreign body-type giant cells, foamy macrophages, fat necrosis
Suture material
What are the features of chronic inflammation?
Increased vascularity and/or fibrosis
Tissue destruction
Lymphoplasmacytic infiltrate
What are some activated forms of macrophages?
Epithelioid
Foamy
Giant cell (langerhans - ring nuclei, foreign body-type - scattered nuclei)
How do histiocytes normally appear?
Bland, fading into the background. Granular cytoplasm (phagocytosed junk).
Stream in a circular pattern.
Can be foamy (almost signet-ring like)
What can cause granuloma formation?
Mycobacterial and fungal infection
Autoimmune disease
Sarcoidosis
Toxins & irritants
How d o granulomas appear?
Aggregate of histiocytes with surrounding lymphocytes & plasma cells.
Giant cells are helpful but not essential.
Old granulomas can become hyalinized and acellular.
Describe the appearance of the following fungi:
Candida
Aspergillus
Mucor
Candida: Round-to-oval yeast forms and pseudohyphae (segmented and nonbranching) at the epithelial surface.
Aspergillus: Long, thin hyphae with 45-degree branching and septation. Can be a solid ball or as single hyphae.
Mucor: Irregular and wide nonseptate hyphae. Almost invisible on H&E.
Describe the appearance of the following fungi:
Histoplasma
Cryptococcus
Pneumocystis
Histoplasma: Tiny intracellular yeast forms with narrow-based budding, either within acrophages or granulomas
Cryptococcus: Encapsulated yeast forms with narrow-based budding, with high size-variability (but larger than histoplasmosis)
Pneumocystis: Flattened, contact-lens shaped in the alveoli. Invisible on H&E but accompanied by foamy pink exudate.
Describe the appearance of:
Helicobacter pylori
Actinomyces
H. Pylori: Tiny seagull-shaped bacilli in pit lumens or surfaces of a background of chronic inflammatory infiltrates.
Actinomyces: Puffball bacterial colony; granular grey-purple, sometimes filamentous, with no identifiable structures.
Distinguish between the appearances of HSV and CMV.
HSV: Infects epithelium (look adjacent to ulcer), which become multinucleated with glassy nuclear inclusions.
CMV: Also infects mesenchymal cells (look in ulcer bed), which are enlarged with large nuclei and dense round inclusion within nucleus with a pale halo.
Describe the appearances of giardia, trichomonas, and cryptosporidium.
Giardia: Flounder with a long tail; kite-shaped at the luminal surface of villi without much inflammation.
Trichomonas: Like giardia, on pap smears
Cryptosporidium: Tiny round parasites along the brush border in the duodenum.
Acute inflammation & abscess formation
- Neutrophils
- Extravasated blood
- Prominent capillaries
- Fibrin accumulation
Granulation tissue
Arrow: Condensing/thickening of the stroma around capillaries
Biopsy site changes
Arrow: Foamy histiocyte ingesting some residual fat
Inset: Hemosiderin in macrophages
Dermal scar
Note displacement of subcutaneous fat and adnexal structures
Histiocytes (circle) amongst lymphocytes (arrowhead)
Granulomas in Crohn’s disease; subtle (arrow) with a collar of lymphocytes
Granulomas in sarcoidosis. Obvious, well-defined masses of pink histiocytes with giant cells (arrowhead)
Granuloma in TB. Histiocytes only visible at periphery, as core is necrotic (arrow).
Hyalinized granuloma
Candida (PAS)
Arrow: Pseudohyphae & yeasts
Aspergillus (GMS)
Note branching hyphae
Mucor (PAS)
Note thick, “hollow” irregular outlines
Histoplasmosis (GMS)
Tiny yeasts (40x objective)
Cryptococcus (GMS)
Note larger organisms than histoplasmosis (still 40x) and range of sizes & shapes
Pneumocystis (GMS)
Lung tissue…
Describe the appearance of TB and MAC.
TB: Bright wine-red, tiny scattered bacilli on AFB. Must scan entire slide at 40x… consider auramine-rhodamine if AFB is negative.
MAC: Profound proliferation within “foamy” macrophages. Can look like Whipple’s disease, but PAS-negative.
Mycobacteria (AFB)
H. Pylori in gastric mucosal pits
Actinomyces
Herpesvirus
Arrow: Multiple molded nuclei with peripheral rim of chromatin and glassy inclusion nearly replacing chromatin
Cytomegalovirus
Arrow: Central reddish-dense nuclear inclusion, surrounded by clear halo and rim of purple chromatin
