26 - Therapeutic and Diagnostic Tests Flashcards
Biopsy techniques
o Curettage o Shave/saucerization o Punch o Direct Immunofluorescence o Nail for fungus
Why biopsy?
- 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
New world of medicine
- 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!
How to biopsy
- 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”
Local anesthesia
- 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
Curettage
- 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
Shave biopsy
- Most common technique for pigmented lesions and tumors – MAIN tool in your tool box ***
Advantages of shave biopsies
o Allows for assessment of lesion borders
o Excision of small lesions, very quick procedure
Disadvantages of shave biopsies
o Difficult to master depth and evaluate dermal components
o Especially tricky in acral sites
A ‘planning’ biopsy
o Guide future therapies
o Diagnostic, occasionally therapeutic
o Caution against re-shaves
Saucerization procedure
o Basically a deep shave biopsy
o Do not go to fat – poor healing
Wheal anesthesia
o Consider inking before biopsy because wheal can mask primary lesion and create confusion
Hemostasis following shave biopsy
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
Wound care
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
Pigmented lesions
- 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
Summary of pigmented lesion shave biopsy
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
ABCDs of melanomas
- A = asymmetry
- B = border irregularity
- C = color
- D = diameter (1/4 inch or 6 mm)
Melanoma
- 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
Spitz nevus
- Head and extremities of children
- Benign, but looks complex histologically – hard for pathologists to diagnose and predict
Blue nevus
- Benign, distinctive, darkly pigmented, patients will be concerned about these
Summary of pigmented lesion shave biopsy KNOW FOR EXAM ***
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
Acral pigmented lesions
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
Diagnoses I (routinely) make
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)
Punch biopsy
- Used for lesions with dermal and subcutaneous components
- Healing can be better
- Only useful when can remove entire lesion
- Beware of partial sampling
Punch situations
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
Admonitions - Warnings for a punch biopsy
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
Blister evaluation
** 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
Bullous pemphigoid
Pathogenesis
o Autoantibody against bullous pemphigoid antigens BP180 and BP230
Pathology
o * Subepidermal blister with eosinophils*
Characteristics of bullous pemphigoid
- 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
Vasculitis
- PALPABLE PURPURA
- Can resemble other entities – targetoid, blisters, pustules
- Biopsy confirmation (lesional DIF)
- Immunofluorescence will show IgM or C3
Advantage of excisions
o Total Removal
o Therapeutic – after diagnosis established
Disadvantages of excisions
o Time intensive
o More vigilant wound care
o Not a practical first line diagnostic tool
CAUTION with excisions
***8
Caution: Avoid “Re-shaving” excisions DO NOT RE-SHAVE
Incisional biopsy
Deep visualization o Panniculitis (EN), soft tissue tumors
Excisional biopsy
- 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
Onychomycosis
“I won’t go into this that much since Dr. Milless went into this
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
Nail specimen collection
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.
Nail biopsy for fungus summary
o Not recommended to treat a patient with terbinafine without diagnostic confirmation
o Cannot make diagnosis of onychomycosis on clinical grounds alone
