Diagnostic Methods and DermPath

Question 1

Special stain(s) that highlight collagen

Answer 1

Masson’s trichrome

Question 2

Special stain(s) that highlight elastin/elastic fibers

Answer 2

Verhoff’s Elastic Stain

Question 3

Special stain(s) that highlight melanin

Answer 3

Fontana-Masson; Gomori methenamine silver stain

Question 4

Special stain(s) for calcium

Answer 4

VonKossa Stain

Question 5

Special stain(s) for lipids

Answer 5

Oil Red O

Question 6

Special stain(s) for acid-fast bacteria

Answer 6

Ziehl-Neelsen, Kinyoun’s method, Fite stain, Auramine stain

Question 7

Special stain(s) for fungi

Answer 7

Gomori methenamine silver stain, Periodic acid-Schiff

Question 8

What components of a sample does hematoxylin stain? What color?

Answer 8

Is a basic dye with a purplish blue color that stains ACIDIC structures such as the cell nucleus and organelles that contain RNA such as ribosomes and rough endoplasmic reticulum – stains them PURPLE

Question 9

What components of a sample does eosin stain? What color?

Answer 9

Is an acidic dye that stains BASIC structures such as the cytoplasm, cell walls, and extracellular fibers – stains them REDDISH PINK

Question 10

What is the Giemsa stain used for?

Answer 10

useful in identifying parasites or pathogenic bacteria; used in blood films including peripheral blood smears and bone marrow aspirates

Question 11

What structures are Congo red stains used for?

Answer 11

amyloid fibrils (gives apple-green birefringence under polarized light); stains cell wall of fungi and outer membrane of gram-negative bacteria

Question 12

What accounts for the different colors between gram-negative and gram-positive bacteria when a gram stain is applied?

Answer 12

Gram positive = thick peptidoglycan layer in cell wall that retains crystal violet stain; Gram negative = thinner peptidoglycan layer allows the crystal violet to be washed away when ethanol is added, then pick up the pink/red counterstain instead

Question 13

Give 8 differentials for infectious organisms associated with Splendore-Hoeppli reactions on biopsy

Answer 13

Zygomycosis (Rhizopus, Mucor, Basidiobolus, Conidiobolus), Habronema (and other cutaneous larval migrans), Sporotrichosis, Blastomycosis, Aspergillosis, Dermatophytic/Bacterial pseudomycetomas, Nocardiosis, Actinomycosis, Pythiosis (not as striking), Lagenidiosis (not as striking)

Question 14

What is the Splendore-Hoeppli reaction?

Answer 14

brightly eosinophilic material that surrounds organisms – represents an antigen-antibody reaction around infectious agents or parasites; occurs at the periphery of organized aggregates of organisms

Question 15

What are the components of the DiffQuick staining solution?

Answer 15

Methanol = clear or pale blue fixative; Eosin = red dye; Methylene blue = blue dye

Question 16

Explain how the D forms in a D test. What enzyme change occurs?

Answer 16

Diffusion of erythromycin in the plate closer to clindamycin results in induction of
methylase (which alters the 50S subunit on the ribosome which both antibiotics bind to in
order to kill the bacteria); The Zone 1 bacterial resistance creates the “D shape” and does not spread farther because
higher concentrations of clindamycin reach the inner zones (Zone 2) and inhibit bacterial growth before the erythromycin can induce resistance in the bacteria to clindamycin as well

Question 17

What is the mechanism of action of methanol as a fixative in staining?

Answer 17

It is a denaturing fixative = removes water from cells and preserves secondary structure
while altering tertiary structure

Question 18

What bacteria can fluoresce with a Wood’s lamp?

Answer 18

Pseudomonas aeruginosa and Corynebacterium minutissimum (but NOT characteristic apple-green of dermatophytes)

Question 19

What is the difference between ectothrix vs endothrix invasion with dermatophytes

Answer 19

Ectothrix = hyphae in the hair shaft form arthroconidia on the hair surface; Endothrix = hyphae in the hair shaft form conidia within the hair shaft leaving the cuticle
intact

Question 20

What species of dermatophytes cause ectothrix invasion?

Answer 20

Microsporum gypseum, Trichophyton verrucosum, T. mentagrophytes

Question 21

What species of dermatophytes cause endothrix invasion?

Answer 21

Trichophyton tonsurans

Question 22

What are 3 fungi that won’t grow on a DTM plate? Why?

Answer 22

They are sensitive to cycloheximide; Cryptococcus neoformans, Candida spp., Aspergillus spp., Zygomycetes (Rhizopus, Mucor spp., Basidiobolus, Conidiobolus)

Question 23

A pigmented fungal organism is present on biopsy, but is not a dermatophyte. What is your next most common differential?

Answer 23

Aspergillus

Question 24

What is Dunstan’s blue line?

Answer 24

area of stratum corneum lifted by degenerate neutrophils and cocci, indicating a staph infection

Question 25

How is direct immunofluorescence staining performed?

Answer 25

incubate cells with an antibody directly conjugated to a

fluorochrome

Question 26

How is indirect immunofluorescence staining performed?

Answer 26

cells are incubated first with a primary antibody, then

again with a secondary fluorochrome-labeled antibody

Question 27

Define immunohistochemistry

Answer 27

antibodies specific for certain epitopes applied to histopathology sections

Question 28

Diagnostic that evalutes tissue samples for presence of intralesional immunoglobulins and/or complement factors using fluorescent-coupled antibodies

Answer 28

Direct immunofluorescence

Question 29

Diagnostic that uses Immunohistochemistry or immunofluorescence to evaluate autoantibodies revealed on the lamina lucida or lamina densa in the basement membrane

Answer 29

salt-split skin

Question 30

Diagnostic that evaluates fixed samples ultrastructurally to identify cellular and extracellular matrix changes

Answer 30

electron microscopy

Question 31

Diagnostic that uses complementary molecular probes to detect sequences of certain chromosomal regions or genes (DNA or RNA), typically on fixed tissue

Answer 31

in situ hybridization

Question 32

Diagnostic that evaluates sera for the presence of tissue specific circulating autoantibodies

Answer 32

indirect immunofluorescence

Question 33

What stain highlights glycogen, mucopolysaccharides, fungi, and tissue debris as red?

Answer 33

Perioidic-Acid Schiff

Question 34

What stain highlights lipids as red?

Answer 34

Oil Red O

Question 35

What stain highlights elastin as black?

Answer 35

Verhoff’s Elastic Stain

Question 36

What stain highlights lipids as green-black?

Answer 36

Sudan black B

Question 37

What stain highlights acid mucopolysaccharides (mucin) as blue?

Answer 37

Alcian blue

Question 38

What stain highlights acid mucopolysaccharides (mucin) and mast cell granules as purple?

Answer 38

Toluidine blue

Question 39

What stain highlights fungi and melanin black?

Answer 39

Gomori methenamine silver stain

Question 40

What color does Gram stain vs Brown-Benn stain highlight gram-postive and gram-negative bacteria?

Answer 40

Gram-postive: Gram stain = purple, BB = blue; Gram-negative: Gram stain = red, BB = red

Question 41

Define prevalence

Answer 41

proportion of cases in a population that have a disease at a given time

Question 42

Define incidence

Answer 42

probability of a disease occurrin in a population over a defined period of time