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CME January 2016 ST

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waderm's version from 2017-02-11 15:22

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Question Answer
DIF is more specific than IIF /ELISA in the diagnosis of pemphigoidF - more sensitive
Perilesional/nonbullous lesional skin is preferred to lesional skin for the diagnosis of bullous pemphigoidT
Brief immersion in formalin produces false positive results in pemphigusF
Michel’s is the preferred medium for DIF specimens received within 48 hoursF - Normal Saline is
For DIF biopsy specimens of the mucosal surface, pick lesions directly adjacent to the erosion/blisterF - pick lesions at least 3-5mm away (precessional skin too friable)
In the diagnosis of bullous pemphigoid, the most sensitive to least sensitive tests are: DIF > ELISA > IIFF - DIF > IIF > ELISA
False positive DIF may be due to bullous scabiesT
DIF, IIF and ELISA have low specificity in the diagnosis of bullous pemphigoidF - specificity almost 100% for all assays
Biopsy specimens for DIF should be taken from perilesional skin within 1cm of the bullaT
Biopsying bullous skin or sites distant to the bulla can result in false positive DIFF - result in false negative
Skin should be taken from above the waist, as biopsying the lower extremities is associated with a higher false negative rateT
A punch biopsy is okay for perilesional skin or for small vesiclesT
Shave biopsy is not appropriate in the diagnosis of immunobullous diseaseF - a scooped shave biopsy into the reticular dermis can be useful to harvest large bullae intact
Specimens for light microscopy should be placed in normal salineF - in formalin
Specimens transported ins aline feature decreased background fluorescence and enhanced specific fluoresenceT
Saline split IIF can only be performed on samples transported in salineF - also in Zeus media or Michel's
Brief immersion in formalin -> false positives in all immunobullous diseaseF - only in pemphigus. Remove and rinse the specimen asap
Immunohistochemistry is as sensitive as DIFF - less sensitive
In the diagnosis of inherited EBA, specimens for EM should be placed in salineF - 2.5% glutaraldehyde solution, stored at 4 degrees overnight
New blisters should be induced when sampling EBAT
It is okay to take samples from the palms/soles in inherited EBAF - try to avoid these sites - difficult to identify cleavege plane and also difficult to induce blister
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Question Answer
In biopsying vasculitic lesions for H&E, the freshest purpuric lesion should be biopsiedF - biopsy established purpuric lesions (>72 hours)
In biopsying vasculitic lesions for DIF, the freshest purpuric lesion should be biopsiedT - <24 hours old. However, IgA vasculitis often retains positive findings in established lesions
Doppler localisation and harvesting a 1cm segment in temporal arteritis helps to increase biopsy yieldF - 2cm segment
Endothelial necrosis and deeper arteriole involvement is more commonly seen in septic vasculitis as well as rheumatoid and antienutrophilc cytoplasmic antbody associated vasculitisT
After 48 hours, inflammatory infiltrate in lekocytoclastic vasculitis shifts from lymphocytic to neutrophilicF - other way around
In biopsying patients with livedo racemosa, take a sample from the pale centre of the erythematous ringT
If there is ulceration in vasculitis, take a sample directly from the centreF - nonspecific changes will be seen, take a sample with the edge of the ulcer
In biopsying panniculitis, a double punch technique or an electric rotary power punch are alternatives to deep incisional biopsyT
It is appropriate to biopsy a child with classic erythema nodosum with no other signs or symptomsF - won't change management
Gelfoam can be used for haemostasis post biopsyT
An 8mm punch is the smallest size that can be divided for histo and cultureF - 6mm
Culture specimens should be ground, not diced when attempting to locate fungal/AFB'sF - diced, not ground
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Question Answer
In biopsying patients with porphyria, perilesional skin is preferred to lesional skin for DIFF - immune deposits are only present in lesional skin
Biopsying new lesions in discoid lupus provides the highest yield for histopathology and DIF F - lesion at least 6 months old, but preferably still active
In porphyria, there is strong IgM and C3T
A punch biopsy 2-3mm is suitable for discoid lupusF - 4mm or more
The best test to differentiate hypertrophic lichen planus and hypertrophic lupus is DIFT
Superficial/atrophic morphea can be diagnosed on shave biopsyT
Caterpillar bodies are seen in biopsies from DLEF - from PCT
Shave/punch biopsy of an entire bulla is OK for PCTT
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Question Answer
in SJS/TENS established lesions are preferable for biopsyingF - acute lesions
Roof of a blister or sloughed skin can be adequate for diagnosing SJS/TENST - except if generalised FDE is on the ddx - the biopsy needs to extend to subcutaneous fat
Old blisters of any aetiology can mimic SJS/TENST
SSS features a split in the straum corneumF - stragum granulosum
Sampling sloughed skin can be adequate for SSSST
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Question Answer
Vertical sections offer highest yield in pattern alopecia and telogen effluviumF - transverse. Vertical for everything else
For all forms of alopecia, the active advancing border should be avoided as established lesions provide higher diagnosisT
If you suspect DLE on the scalp, DIF should be taken from a fresh lesionF - established but still active lesion (>6mo)
Gelofoam is superior to sutures for haemostasis of scalp biopsyT
In the HoVert technique, the specimen undergoes transverse sectioning and then vertical sectioning of the upper 1mm portionT
In the Tyler technique, there is transverse sectioning of the specimen followed by vertical sectioning of one halfF - vertical first, then transverse one half
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Question Answer
Punch biopsies are preferable to shave biopsies in the diagnosis of suspected BCC/SCCT
The presence of spiky irregular tumour islands, fibroblast rich stroma, sclerotic red stroma are more suggestive of an aggressive underlying growth patternT
In the setting of lentigo maligna, a punch biopsy is preferable to a broad thin shaveF
Acral lesions should be bisected parallel to the dermatoglyphsF - bisected perpendicular, to avoid artifactual appearance of confluence
Excisional biopsies of pigmented lesions on the extremities should be oriented along the longitudinal axisT - reflects pattern of lymphatic drainage and spread
Undermining wound edges in closing a melanoma should be minimised as it can affect sentinel lymph node mappingT
In pigmented lesions with many colours, each coloured area requires samplingT
Nevi on volar skin can be completely removed with saucerisationT
A deep incisional biopsy is required for the diagnosis of DFSPT
Broad shave biopsies are ideal for the diagnosis of CTCLT - need to get to at least the reticular dermis
T cell receptor gene rearrangements can be performed on formalin samplesT, although higher yield with fresh samples
Biopsying multiple sites is helpful in MFT - can show identical clones
large incisional biopsies and in some cases saucerisation or deep punches are appropriate for lesions of cutaneous B cell lymphomaT
At least a 4mm punch is needed when sampling cutaneous B cell lymphomaF - at least 6mm
Samples taken for B cell lymphoma for FISH and PCR gene rearrngement should be sent freshF - send in formalin, can be done in formalin. Flow cytometry will require a fresh specimen
Roswell Park Memorial Institute medium is appropriate for flow cytometry in cutaneous B cell lymphomaT
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