Chapter 3 - Infection & Inflammation

Question 1

What are the features of acute inflammation?

Answer 1

Vascular congestion, edema

Fibrinous exudate, tissue damage & necrosis

Neutrophils

Question 2

What can trigger acute inflammation?

How can it resolve?

Answer 2

Trauma, ischemia, toxins, infection…

Can be followed by resolution, fibrosis/scar, abscess formation, or chronic inflammatory change

Question 3

Describe the appearance of granulation tissue

Answer 3

Watery or myxoid background with inflammatory cells, sparse fibroblasts, and capillaries with prominent endothelium.

Question 4

Describe the appearance of biopsy site changes

Answer 4

Fibroblast proliferation (early scar)

Foreign body-type giant cells, foamy macrophages, fat necrosis

Suture material

Question 5

What are the features of chronic inflammation?

Answer 5

Increased vascularity and/or fibrosis

Tissue destruction

Lymphoplasmacytic infiltrate

Question 6

What are some activated forms of macrophages?

Answer 6

Epithelioid

Foamy

Giant cell (langerhans - ring nuclei, foreign body-type - scattered nuclei)

Question 7

How do histiocytes normally appear?

Answer 7

Bland, fading into the background. Granular cytoplasm (phagocytosed junk).

Stream in a circular pattern.

Can be foamy (almost signet-ring like)

Question 8

What can cause granuloma formation?

Answer 8

Mycobacterial and fungal infection

Autoimmune disease

Sarcoidosis

Toxins & irritants

Question 9

How d o granulomas appear?

Answer 9

Aggregate of histiocytes with surrounding lymphocytes & plasma cells.

Giant cells are helpful but not essential.

Old granulomas can become hyalinized and acellular.

Question 10

Describe the appearance of the following fungi:

Candida

Aspergillus

Mucor

Answer 10

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.

Question 11

Describe the appearance of the following fungi:

Histoplasma

Cryptococcus

Pneumocystis

Answer 11

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.

Question 12

Describe the appearance of:

Helicobacter pylori

Actinomyces

Answer 12

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.

Question 13

Distinguish between the appearances of HSV and CMV.

Answer 13

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.

Question 14

Describe the appearances of giardia, trichomonas, and cryptosporidium.

Answer 14

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.

Question 15

Answer 15

Acute inflammation & abscess formation

1. Neutrophils
2. Extravasated blood
3. Prominent capillaries
4. Fibrin accumulation

Question 16

Answer 16

Granulation tissue

Arrow: Condensing/thickening of the stroma around capillaries

Question 17

Answer 17

Biopsy site changes

Arrow: Foamy histiocyte ingesting some residual fat
Inset: Hemosiderin in macrophages

Question 18

Answer 18

Dermal scar

Note displacement of subcutaneous fat and adnexal structures

Question 19

Answer 19

Histiocytes (circle) amongst lymphocytes (arrowhead)

Question 20

Answer 20

Granulomas in Crohn’s disease; subtle (arrow) with a collar of lymphocytes

Question 21

Answer 21

Granulomas in sarcoidosis. Obvious, well-defined masses of pink histiocytes with giant cells (arrowhead)

Question 22

Answer 22

Granuloma in TB. Histiocytes only visible at periphery, as core is necrotic (arrow).

Question 23

Answer 23

Hyalinized granuloma

Question 24

Answer 24

Candida (PAS)

Arrow: Pseudohyphae & yeasts

Question 25

Answer 25

Aspergillus (GMS)

Note branching hyphae

Question 26

Answer 26

Mucor (PAS)

Note thick, “hollow” irregular outlines

Question 27

Answer 27

Histoplasmosis (GMS)

Tiny yeasts (40x objective)

Question 28

Answer 28

Cryptococcus (GMS)

Note larger organisms than histoplasmosis (still 40x) and range of sizes & shapes

Question 29

Answer 29

Pneumocystis (GMS)

Lung tissue…

Question 30

Describe the appearance of TB and MAC.

Answer 30

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.

Question 31

Answer 31

Mycobacteria (AFB)

Question 32

Answer 32

H. Pylori in gastric mucosal pits

Question 33

Answer 33

Actinomyces

Question 34

Answer 34

Herpesvirus

Arrow: Multiple molded nuclei with peripheral rim of chromatin and glassy inclusion nearly replacing chromatin

Question 35

Answer 35

Cytomegalovirus

Arrow: Central reddish-dense nuclear inclusion, surrounded by clear halo and rim of purple chromatin