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#2 Derm > 26 - Therapeutic and Diagnostic Tests > Flashcards

26 - Therapeutic and Diagnostic Tests Flashcards

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Dermatology Board Prep flashcards
1
Q

Biopsy techniques

A 
o	Curettage
o	Shave/saucerization
o	Punch
o	Direct Immunofluorescence
o	Nail for fungus
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2
Q

Why biopsy?

A
  • Standard of care
  • Cornerstone of dermatologic diagnosis is correlation of clinical and histological findings
  • Patient and Provider Peace of Mind
  • Minimal Tissue Destruction (can be done with local anesthesia)
  • Can be curative (biopsy it “out” or the inflammation from biopsy can activate immune system)
  • Big ‘Bang for the Buck’
  • Low cost, high diagnostic value
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3
Q

New world of medicine

A
  • Insurance companies, ACOs, government, and (increasingly savvy) patients require justification for treatment
  • Examples: Onychomycosis, tumor excisions, payment for lab tests
  • Used to plan future treatment!
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4
Q

How to biopsy

A
  • Need to have a clinical description and differential diagnosis
  • Very difficult for pathologist to help with diagnosis without this – their pet peeve
  • Disease to “rule out”: Bowen’s disease, erythema nodosum, bullous pemphigoid, stasis ulcer
  • Site: Nail vs periungual vs heel vs shin
  • Describe a lesion/eruption – do NOT just write “bump on leg, rash on foot”
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5
Q

Local anesthesia

A
  • All these biopsies are done under local anesthesia
  • Ask about allergies
  • Clean with alcohol
  • Use a 25 gauge needle
  • Usually use 1% lidocaine +/- epinephrine
  • Beware of epinephrine for feet/toes (can cause necrosis in toes)
  • Okay if well vascularized and use less than 1 mL
  • Helps control bleeding
  • Make wheal under lesion (makes biopsy easier)
  • Mark lesion with pen
  • Effect lasts 30-60 minutes
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6
Q

Curettage

A
  • Pretty much, DON’T DO THIS FOR A BIOPSY
  • Destructive, not diagnostic, never appropriate for melanocytic lesions
  • Often used AFTER achieve a diagnosis
  • Example: Curetting the base of a basal cell carcinoma
  • Achieve local anesthesia with a wheal, scrape superficial tissue
  • Healing occurs by secondary intention
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7
Q

Shave biopsy

A
  • Most common technique for pigmented lesions and tumors – MAIN tool in your tool box ***
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8
Q

Advantages of shave biopsies

A

o Allows for assessment of lesion borders

o Excision of small lesions, very quick procedure

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9
Q

Disadvantages of shave biopsies

A

o Difficult to master depth and evaluate dermal components

o Especially tricky in acral sites

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10
Q

A ‘planning’ biopsy

A

o Guide future therapies
o Diagnostic, occasionally therapeutic
o Caution against re-shaves

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11
Q

Saucerization procedure

A

o Basically a deep shave biopsy

o Do not go to fat – poor healing

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12
Q

Wheal anesthesia

A

o Consider inking before biopsy because wheal can mask primary lesion and create confusion

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13
Q

Hemostasis following shave biopsy

A

Aluminum Chloride

Ferric Chloride (Monsel solution)
o	Iron-based solutions can leave residual pigment, so avoid for pigmented lesions

Electrocautery
o Used in excisions, big bleeds, or coumadin patients
o Beware cautery artifact

Place specimen in container with formalin and send to pathologist

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14
Q

Wound care

A

Less than 6% infection rate with cutaneous biopsy (usually within 3 days)

Cover and moisten wound for 1 week
o Petroleum jelly or mupirocin (just as effective)
o Estimated $10 million savings/year if switch to petroleum jelly
o Not neomycin containing ointments (very potent, can get contact dermatitis)

Avoid wetting wound for 2 days

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15
Q

Pigmented lesions

A
  • Single largest risk area: Harm to patients, Malpractice risk
  • **If it is concerning enough to biopsy, it is concerning enough to remove ** Do NOT partially sample a lesion – NOT a good way to sample pigmented lesions
  • Extreme variability from one location to the next within a single lesion
  • Shave or saucerization biopsy
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16
Q

Summary of pigmented lesion shave biopsy

A

Biopsy entire lesion
o No “clean bill of health” on partial biopsies

Exceptions
o Large facial lesion (rule out lentigo maligna)
o Large congenital nevus (rule out malignant conversion)
o Always helpful to provide a map/picture

Always tell the patient to return IMMEDIATELY if site re-pigments

17
Q

ABCDs of melanomas

A
  • A = asymmetry
  • B = border irregularity
  • C = color
  • D = diameter (1/4 inch or 6 mm)
18
Q

Melanoma

A
  • Approach every patient the same every time, regardless of their chief complaint
  • Always look for melanoma on your patients – if you see something, bring it up and look into it
19
Q

Spitz nevus

A
  • Head and extremities of children

- Benign, but looks complex histologically – hard for pathologists to diagnose and predict

20
Q

Blue nevus

A
  • Benign, distinctive, darkly pigmented, patients will be concerned about these
21
Q

Summary of pigmented lesion shave biopsy KNOW FOR EXAM ***

A

Biopsy entire lesion
o No “clean bill of health” on partial biopsies

Exceptions
o Large facial lesion (rule out lentigo maligna)
o Large congenital nevus (rule out malignant conversion)
o Always helpful to provide a map/picture

Always tell the patient to return IMMEDIATELY if site re-pigments

Avoid partial biopsy due to variation within a single lesion
o Curettings, Partial punches, and superficial shaves

Provide map and dimensions if complete removal is not possible

22
Q

Acral pigmented lesions

A

Challenging both clinically and histologically

Stratum Corneum is very thick on palms and soles
o A biopsy must include epidermis and dermis
o Consider excision for larger lesions on heavily cornified areas

23
Q

Diagnoses I (routinely) make

A

o Skin, right plantar foot, biopsy: Hyperkeratosis, superficial sampling.
o Skin, right shin, biopsy: Atypical lentiginous compound nevus, margins negative
o Skin, left dorsal foot, biopsy: Atypical nevomelanocytic proliferation, margins positive.
- High level of worry – maybe nevus, maybe melanoma
- Can’t predict behavior of this – need to cut it out
o Skin, right knee, biopsy: Atypical squamous proliferation, base transected.
- Can’t rule out squamous cell carcinoma, can’t diagnose this
o Skin, left calf, biopsy: Malignant melanoma, at least Clark’s level II, at least 0.81 mm in Breslow’s depth (You will want 1 cm margins)

24
Q

Punch biopsy

A
  • Used for lesions with dermal and subcutaneous components
  • Healing can be better
  • Only useful when can remove entire lesion
  • Beware of partial sampling
25
Q

Punch situations

A

Best procedure for dermatitides
o Dermatitis, vasculitis, blisters (see later), granulomatous disease, connective tissue dz

Has some limited value for deeper processes
o Try if you can get deep – need to get into subcutaneous fat

In eruption with evolution of lesions, consider multiple biopsies
o In large lesions, get expanding border and older center

26
Q

Admonitions - Warnings for a punch biopsy

A

Beware of 2 mm punch
o Very limited diagnostic value
o May be forced to rebiopsy

Beware of very large punches (>5 mm)
o Harder to close
o Consider excision if need a punch that big

Avoid excoriations/ulcers
o Secondary effects mask primary pathology
o This is a big deal – a lot of people struggle with this
o How you biopsy depends on what answers you want… If you want to rule out a squamous cell carcinoma that has come up in the ulcer, you will want to punch the base
o ** Ulcers tend to mask the underlying pathological process **
o Consult with a pathologists when you’re unsure

Avoid pre-treated lesions
o If you’ve given a steroid, it may mask the inflammatory process
o Pathologists can no longer give a diagnostic answer

27
Q

Blister evaluation

A

** NEED TO DO 2 BIOPSIES **

#1 = Tissue biopsy
o	Lesional punch biopsy
#2 = Direct Immunofluorescence
o	Ab against patient’s perilesional skin (punch again – a second punch)

Other tests you can do (don’t worry about): Indirect Immunofluorescence (circulating Ab against normal skin), electron microscopy, serology studies

28
Q

Bullous pemphigoid

A

Pathogenesis
o Autoantibody against bullous pemphigoid antigens BP180 and BP230

Pathology
o * Subepidermal blister with eosinophils*

29
Q

Characteristics of bullous pemphigoid

A
  • Most common bullous autoimmune disease
  • Age: 60-80+, sex: M=F
  • Direct immunofluorescence will show linear deposition of IgG and C3 along the basement membrane zone

History and physical

  • Prodromal eruption
  • Urticarial/papular lesions
  • Evolves over weeks/months to a generalized bullous eruption
  • Rare involvement of mucosal surfaces
  • Moderate to severe pruritus
  • Tense bullae arise in normal or erythematous skin
30
Q

Vasculitis

A
  • PALPABLE PURPURA
  • Can resemble other entities – targetoid, blisters, pustules
  • Biopsy confirmation (lesional DIF)
  • Immunofluorescence will show IgM or C3
31
Q

Advantage of excisions

A

o Total Removal

o Therapeutic – after diagnosis established

32
Q

Disadvantages of excisions

A

o Time intensive
o More vigilant wound care
o Not a practical first line diagnostic tool

33
Q

CAUTION with excisions

***8

A

Caution: Avoid “Re-shaving” excisions DO NOT RE-SHAVE

34
Q

Incisional biopsy

A 
Deep visualization
o	Panniculitis (EN), soft tissue tumors
35
Q

Excisional biopsy

A
  • You WANT to go into the fat for an excision, you do NOT want to go into the fat for a shave
  • 3-4:1 ratio
36
Q

Onychomycosis

“I won’t go into this that much since Dr. Milless went into this

A

Very common
o 2-13% of population, 50% of all nail disorders
o Toenails 4x greater than fingernails

Distal subungual onychomycosis
o 90% of cases

Fungal Infection
o	Trichophyton rubrum
o	Trichophyton mentagrophytes
Diagnosis
o	Histological examination of clipped or curetted nail fragments is most sensitive method (Use of PAS - stains the colorless carbohydrates of fungal cell walls bright red - PAS histopathological examination is accepted standard of care and increasingly required by insurance companies

Mimickers of onychomycosis
o Yellow nail syndrome, idiopathic onycholysis, psoriasis, lichen planus, traumatic onychodystrophies, nailbed tumors (SCC), contact dermatitis

37
Q

Nail specimen collection

A

o Cleanse affected nails with alcohol or soap/water and dry
o Clip nail to most proximal point possible without discomfort
o Collect subungual debris by scraping with curette or blade
o Pathophysiology: Nailbed keratinization is a precursor of fungal infection and dermatophytes first colonize that tissue.

38
Q

Nail biopsy for fungus summary

A

o Not recommended to treat a patient with terbinafine without diagnostic confirmation
o Cannot make diagnosis of onychomycosis on clinical grounds alone

#2 Derm (13 decks)

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