Skin Analysis Techniques Flashcards
Calciphylaxis
- Disease in which calcium accumulates in small blood vessels of the fat and skin tissues
- Causes blood clots, painful skin ulcers and may cause serious infections that can lead to death
People who have calciphylaxis usually have
- Kidney failure and are on dialysis or have had a kidney transplant
- Condition can also occur in people without kidney disease
Mimics of cellulitis
- Stasis dermatitis (acute)
- Lipodermatosclerosis
- Contact dermatitis
- Dermatohypersensitivity reaction
- Lymphedema
- Gout
- Erythema migrans
- Cryptococcal cellulitis
- Calciphylaxis
Dermatoscope
- Handheld magnifying device (typically 10×) which uses an oil medium or cross-polarised light allowing the viewer to observe structures deeper in the skin, not normally visible to the naked eye
Dermatitis Tx option
- Pharmacological
Neoplasm Tx option
- Surgical excision
Ideally, you should biopsy
- Any inflammatory lower extremity disorder with a questionable diagnosis
- Any blistering “rash”
- Any suspicious neoplasm
Common biopsy techniques
- Punch biopsy
- Shave biopsy
- Saucerization (a form of shave biopsy)
- Curettage
- Core needle
- Aspiration biopsy
Choosing which biopsy technique to use
- In general terms, when a small part of a patch or plaque is sampled for histopathology, a punch biopsy is the technique of choice
General biopsy rule
- Only large lesions are punched
- Small are shaven
Verrucous lesions on plantar surface
- Tend to by endophytic (grows inward)
- Shave biopsy may not sample deep enough to obtain diagnostic info
- Punch biopsy better to distinguish lesions that may mimic each other
A punch biopsy is a common technique used to sample conditions that
- Are too large to be shaven
- Have a deep dermal component (requiring deeper sampling)
Punches may be used to sample
- Suspected vasculitis
- Ulcers
- Large pigmented lesions (those too large to be shaven)
- Other large suspected neoplasms (those that are greater than 1cm in diameter)
3-millimeter punches are used for
- Epidermal nerve fiber density testing
Small punches (2mm) are ideal for
- Plantar verrucous lesions
- Because this technique samples the full thickness of such plantar lesions, it allows Dermatopathologists to accurately discriminate between genuine verrucae and clinically identical verrucous carcinomas
In summary, punch biopsies are ideal when
- A small part of a much larger lesion is submitted for histopathology
Standard shave biopsies
- Used more commonly in dermatologic practices than punch biopsies
- Combination of standard shaves and saucerizations represents the overwhelming majority of biopsies performed by dermatologists
Shaves do not routinely sample the deep dermis
- They typically extend only to the depth of the superficial dermis
Always make sure pt has _____ before punch biopsy
- Arterial perfusion
Where punches are relatively narrow (most punches are 2-4mm in diameter), shaves often encompass
- A broad sample of superficial skin (often 1cm or greater in width)
Shave technique is the ideal sampling method for
- Unexplained papules (elevated lesions measuring 5mm or less in diameter)
- Can be used for macules (flat lesions measuring less than 1cm in diameter)
Saucerization
- Closely related to a standard shave biopsy
- Uses a bendable blade, not dissimilar to a Gillette razor blade, to “scoop out” the tissue of concern
- Better for flat or endophytic (inward growing) lesions
- More aggressive, can be considered more of an excision
Curettage
- Less common sampling method
- Uses a dermal curette to scrape the surface of the skin to obtain the desired tissue sample
Curettage disadvantage
- Specimens may be difficult to histopathologically examine
- Inherent fragmentation of the sample
- May make the tissue impossible to correctly orient
- Used with non-healing wounds
Core needle biopsy
- ideal method of diagnosing more deeply seated masses
- Perfect for investigating tumors of the soft tissue
- Essentially any mass that falls into the differential diagnosis with a lipoma or ganglion could be sampled using core needle technique
Core needles
- Hollow large gauge needles designed to withdraw thin columns of tissue from within the mass in question
To obtain tissue using core needle biopsy
- The skin overlying the mass is incised and the instrument is inserted to abut the mass in question
Core needle mechanism
- Depending on the size of the mass, the biopsy instrument is set by the clinician to sample to a desired depth using a spring loaded mechanism
- The device is discharged and the sample is obtained
- This is usually repeated into the masses’ various quadrants
Needle aspiration biopsy
- Underutilized diagnostic procedures of those available
- May be effectively used to rule out high‐grade malignancies when faced with nonspecific subcutaneous masses (in particular, those masses that resemble ganglion cysts)
Neoplasms masquerading as ganglion cysts may fool clinicians
- Roughly 70% of all the soft tissue masses in the foot are ganglia
Needle aspiration differs somewhat from most other biopsy techniques in that
- It provides the pathologist with cells and tiny tissue fragments to review, rather than large pieces of tissue
- Cytopathology can be somewhat less specific than histopathology
The pathology reports derived from aspiration specimens typically provide
- Basic, though highly significant information
- “malignant cells not identified”, “atypical cells identified”, or “malignant cells identified
Practice guidelines have recommended performingwound biopsiesfor histological diagnosis or microbiologic testing inwoundsthat havenotimproved within
- 3 to 6 weeks of appropriate management
If a wound you are seeing for the first time exhibits clinical signs of malignancy (ABCDE)
- Asymmetry
- Irregular border
- Color variation
- Diameter
- Evolving
- Biopsy immediately (if not, treat based on presumed etiology)
Diagnosis onychomycosis
- Can be confirmed by direct microscopic examination with a Potassium Hydroxide (KOH) wet-mount preparation
- Histopathologic examination of the trimmed affected nail plate with a Periodic-Acid-Schiff (PAS) stain
- Fungal culture
- PCR assays
Ideal test for diagnosing onychomycosis would
- Identify the fungus and the species
- Determine its viability
- Be easy to perform with rapid result and low cost
- Be highly specific and sensitive
Woods light
- Helps to differentiate between interdigital erythrasma and Tinea pedis
Erythrasma
- Superficial skin infection cause byCorynebacterium minutissimum
Erythrasma most commonly affects
- Plantar feet and interdigital areas
- Most common cause of interdigital bacterial infection on the feet
- Most often visible between the fourth and fifth toes
Interdigital erythrasma
- More difficult to diagnose as the web spaces become macerated
- Common to see concurrent infections with a bacteria and dermatophyte
Interdigital erythrasma differential diagnosis
- Psoriasis
- Dermatophytosis
- Candidiasis
- Intertrigo
Tx of erythrasma
- Typically begins with topical agents
- Research has shown that related species ofCorynebacteriumare sensitive to topical clindamycin
Erythrasma Tx schedule
- Applying topical clindamycin 1% gel or cream to the affected area two to three times a day for two to four weeks effectively eradicates most infections
- Alternative topical treatments include erythromycin 2% gel and Whitfield’s ointment
Key elements of wound infection
- Occurs in wound tissue, not on the surface of the wound bed
- Occurs in viable wound tissue; it isn’t a phenomenon of necrotic tissue, eschar, or other debris contained in the wound bed
- Caused by invasion and multiplication of microbes in the wound
- Manifested by a host reaction or tissue injury
Three techniques that can be used to identify colonization or infection
- Deep tissue or punch biopsy
- Needle aspiration
- Swab culture
Swab culture technique
- Most commonly used because it is practical, simple, noninvasive and cost effective
Swab culture of a chronic wound may not identify
- All types of microbes
- Does not identify any microbial load in the deep tissue
- May only identify surface bacteria
Gold standard in identifying bacteria in the wound bed
- Wound biopsy sent for culture and sensitivity testing
Methods of swab culture
- Z stroke technique
- Levine’s technique
Z stroke technique disadvantages
- Less optimal
- Likely to pick up organism from necrotic tissue if present, skin edges
Z stroke technique
- Swab should be rotated between the fingers as the wound is swabbed from margin to margin in a 10-point, zigzag fashion
- Because a large portion of the wound surface is sampled, the specimen collected may reflect surface contamination rather than tissue bioburden.
Levine’s technique
- Surface swab of a once cm^2 area of healthy tissue in the wound
- Press into wound to obtain fluid
Levine technique methods
- Swab is rotated over a 1-cm square area with sufficient pressure to express fluid from within the wound tissue
- Believed to be more reflective of tissue bioburden than swabs of exudate or swabs taken with a broad Z-stroke
Theoretically, the Levine technique is the best technique for wound swabbing, provided
- The wound is cleansed first
- The area sampled is over viable tissue, not necrotic tissue or eschar
The swab technique most consistent with the key elements of wound infection is
- Levine’s technique
- Attempts to sample microorganisms from within the wound tissue, not just from the wound surface
Molecular methods advantages over agar cultures
- Accuracy
- Rapid results
- High sensitivity
- High benefit to expense ratio, specificity and availability
- Quantitative
Molecular methods are singularly suited to diagnose
- Polymicrobial and biofilm associated clinical infections
Polymerase chain reaction (PCR)
- Molecular technique utilized to target and “amplify” a single or few copies of a piece of DNA, generating thousands to millions of copies of a particular DNA sequence thereby allowing them to be detected
PCR benefits
- Bacteria are identified by “amplifying” their DNA, requiring only a tiny sample, without actually having to grow bacterial cultures in the microbiology laboratory
- This technology is sensitive, specific and can be done in hours
