Dr Richard Carr

Histological Approach to the Diagnosis of 

Spongiotic and Psoriasiform Dermatoses 

Dr Richard Carr 

Warwick Hospital

“Unfortunately, Fortunately dermatopathology requires 

years of training and practice to achieve an 

acceptable level of diagnostic skill.” 

Endless number of diagnoses! 

Bewildering terms! 

Overlapping histological features! 

“logical approach, majority can be 

diagnosed specifically and remainder 

placed into a particular group of diseases”

•Definitions 

•General Approach 

•Secondary changes 

•Spongiotic cases 

•Psoriasiform cases 

•Summary 

What‘s to come...

Definitions: Spongiotic 

• Intercellular oedema 

(epidermis &/or epithelial 

structures of adnexa) 

• Separation of spinous 

cells 

• Intercellular bridges 

conspicous 

• Sprinkling of 

inflammatory cells 

– Usually lymphocytes 

– +/- Eosinophils 

– +/- Neutrophils

Definititions: 

Psoriasiform Epidermal Acanthosis 

• Elongated rete ridges of about equal length that 

alternate with long dermal papillae to form a strikingly 

undulate pattern: A) Even; B) Uneven

General (Algorithmic) Approach 

Dr A. Bernard Akerman 

c/o Richard Perry/The New York Times 

6

Akerman: Algorithmic 

Approach 

• Identify one of the (nine) patterns 

• Refer to the algorithm for that pattern 

• Follow the branches of the algorithm to 

a specific diagnosis 

• Read up the features of the diagnosis 

and correlate with clinical and 

histological details of the case. 

• If the diagnostic criteria are not fulfilled 

go back to the algorithm and start again

Diagnostic Approach to Inflammatory Skin: Logical & Algorithmic 

Reaction Pattern 

e.g. Psoriasiform (only) 

Psoriasis 

Cell Type 

e.g. Lymphocytes 

predominate 

List of Diseases 

Chronic (spongiotic) dermatitis: 

Allergic contact / numular / 

dyshidrotic / photoallergic; 

AIDS associated psoriasiform 

dermatitis; Pityriasis rosea (herald 

patch); Pityriasis rubra pilaris; 

Seborrhoeic dermatitis; External 

trauma (LSC etc); Deficiency 

diseases; Dermatophytosis; 

Candidiasis 

RAC2383




Psoriasis 

Cell Type 


predominate 











Candidiasis 

Detailed Features 

Parakeratosis & loss of granular layer 

Marked regular acanthosis & fusion of rete ridges 

Thin supra-papillary plate 

Long oedematous dermal papillae 

Dermal papillae club shaped at tip 

RAC2383




Psoriasis 

Cell Type 


predominate 











Candidiasis 



Munro microabscesses 

Small spongiform pustules (Kogoj) 

RAC2383




Psoriasis 

Cell Type 


predominate 











Candidiasis 



Small spongiform pustules 

Marked regular acanthosis & fusion of rete ridges 

Thin supra-papillary plate 

Long oedematous dermal papillae & dilated vessels 

Dermal papillae club shaped at tip 

1 st Differential 

Psoriasis (plaque type) 

Dermatophytosis; Candidiasis 

Clinical Correlation 

?

F36 Axilla, hidradenitis supurativa Home Diagnosis & Dry?? 

Known 

to have 

psoriasis! 

Clinical analysis of 48 cases of inverse psoriasis: a hospital-based study 

European Journal of Dermatology. Volume 15, Number 3, 176-8, May-June 2005, 

Clinical report 

Gang Wang, Chunying Li, Tianwen Gao, Yufeng Liu 

RAC2383

LEARNING POINTS 

Dermatologists rarely biopsy classical 

dermatoses! 

GPs do but should be discouraged!!

Learning Resources 

• A. Bernard Ackerman 

– The Gold Book: 1978 

– Silver Book: 1997 

– Gold/Silver/Internet: 2005 

• Derm101.com 

• Essential reading for 

anyone wanting to really 

get to grips with 

inflammatory skins

Lever 

• Mutli-author has it’s 

drawbacks 

• Image quality 

variable 

• Excellent set of 

algorithms 

• Then use Weedon or 

Mckee! 

• Website limited

Weedon 

• Near single author 

continuity 

• Encyclopaedic 

– separate volume for 

references! 

• Excellent introductory 

chapters on approach 

• Good set of clues and 

algorithms 

– Modified from Akerman 

pattern

Mckee & Calonje 4 th 2012 

• Clinical images 

• Exceptional image 

quality 

• Encyclopaedic 

• Lacks introductory 

chapters on pattern 

analysis and 

algorithms 

– Still will help to read 

Ackerman though!

Secondary Changes 

24

Excoriation only...

M52. ?Dermatofibroma left shin

Lichenification 

(Lichen Simplex Chronicus)

CRYPTIC 

Clue: Hairy Palm Sign 

Marked orthohyperkeratosis in which packed anucleate 

compact keratin on hair bearing skin, indicates a response to 

prolonged vigorous rubbing 

• Lichen simplex (RUB) 

• Prurigo nodularis 

(SCRATCHING) 

DIAGNOSTIC 

“ITCHY” CONDITIONS 

– “Hypertrophic” LP 

– DLE 

– Lichen Sclerosus 

– Dermatophytosis 

– Lichen amyloidosis 

– Mycosis fungoides 

– etc, etc

Lichen Simplex Chronicus 

• Localised areas of 

thickened skin 

• “tree bark” 

• Severe pruritis 

• Accessible sites: 

lower legs, ankles, 

vulva, scrotum

Lesion on the ankle, 2/12 after visit to S. Africa. 

Vesicles exudes gelatinous fluid. 

RAC4386

Nodular Prurigo / 

Pseudoepitheliomatous hyperplasia 

(PEH) overlying ganglion cyst

Nodular 

Prurigo 

• Chronic 

• Intensely itchy 

• Lichenified, excoriated 

• Papules and Nodules 

• Overlaps with lichen 

simplex chronicus 

• Associations 

– Often otherwise well 

– Rarely associated gluten 

sensitive enteropathy 

– Psychosocial factors 

– Preceding insect bite 

– Itchy dermatoses 

– Overlying Tumours (BCC)

F86 Left ankle lesion. Biopsy proven squamous cell 

carcinoma 

RAC4386-2

So far so good….

Diagnosis 

Polypoid eccrine poroma with 

florid pseudoepitheliomatous 

hyperplasia (PEH) 

RAC4386-2

• Difficult! 

PEH Learning Points 

• Be humble and don’t 

be afraid to say don’t 

know 

• Advise repeat biopsy 

or conservative 

excision for definitive 

diagnosis

Spongiotic Dermatoses 

42

Spongiotic (“eczematous”) Pattern 

• Most common 

pattern 

• Most difficult to 

arrive at a specific 

diagnosis

Eczematous (Spongiotic) Dermatitis 

• Clinical group 

characterised by 

– Pruritic vesicles, 

– Rupture forming crusts 

– Erythematous base 

– Become “lichenified” in 

chronic cases

Eczema “aetiological” Groups 

ENDOGENOUS 

• Atopic dermatitis 

• Seborrhoeic dermatitis 

• Discoid (nummular) 

dermatitis 

• Hand eczema 

(dishidrotic, pompholyx) 

• Autosensitization (Id) 

reaction 

EXOGENOUS 

• Allergic contact 

• Irritant contact 

• Infective (S. aureas) 

• Asteatotic eczema

Eczematous (Spongiotic) Dermatitis: 

Histological Subclassification 

• Acute 

– Vesiculation and bullae 

• Subacute 

– Acanthosis, spongiosis and vesicles 

common 

• Chronic 

– Spongiosis (subtle), vesicles uncommon 

– Psoriasiform epidermal acanthosis

Spongiosis 

Vesicle (Acute) 

RAC3123 

• Accumulation of fluid within 

the epidermis leads to a 

vesicle

Subacute/Chronic Spongiotic Psoriasiform 

(Lichenified “eczematous”) 

RAC3254

Spongiotic Dermatitis: Late 

• Chronic rubbing and scratching leads to scaly 

and thickened lesions 

– Lichenification dominates 

– Psoriasiform pattern with minimal spongiosis

M85. Raised annular patch with central hypopigmentation. 

Multiple other patches on arms and legs. ?Discoid eczema. 

?Discoid lupus. 

RAC5806

“Mild to moderate spongiosis. Mild superficial perivascular 

lymphocytic 

infiltrate with occasional eosinophils, in keeping with (numular / 

discoid) eczematous dermatitis” 

PAS stripsx3 to r/o fungal hyphae 

c/w Eczematous (spongiotic) dermatitis

Discoid (Nummular) 

Dermatitis 

• Single or multiple pruritic 

lesion 

• Discoid/coin shaped 

• Lower legs, forearms, 

hands (dorsum) 

• Young women and middle 

aged adults 

• Chronicity 

• Causes/Associations: 

Idiopathic, atopy, contact 

irritants (soap, acids etc), 

contact allergy (e.g. metals)

M30. Recurrent blisters on foot. ? EBA 

RAC3123 

c/o Dr Niamh Leonard

Acute spongiotic vesicular dermatosis. 

“Could this be… 

Pompholyx 

RAC3123 

c/o Dr Niamh Leonard

Hand Eczema 

(pompholyx, dyshidrotic, palmoplantar) 

• Pruritic 

• Tense vesicles (papular 

lesions) 

• May progress to 

cracking/scaling 

• Causes/Associations 

– Unknown 

– Heat/psychological stress 

– Atopy 

– Hyperhidrosis 

– Dermatophytosis (tinea 

pedis)

Autosensitization (Id) Reaction 

• Generalized spongiotic dermatitis in response 

to a dermatosis or infection elsewhere 

• Resolves with treatment of the 

“preciptating/associated” disease 

• Lesions may be localised e.g. pompholyx 

• Associations 

– Fungal infections (dermatophytes) 

– Scabies 

– Molluscum 

– Tick bite 

– Pediculosis capitis 

– Bacterial & mycobacterial

Spongiotic (Intraepidermal) Vesicles 

• Allergic Contact 

dermatitis 

• Photoallergic, early 

• Nummular dermatitis 

(discoid eczema) 

• Dyshidrotic dermatitis 

– Hand eczema, pompholyx 

• “id” reactions 

• Dermatophytosis 

• Arthropod assaults

Learning Points 

• Dermatologist usually right 

• …..But not always 

• Don’t be afraid to make suggestions 

• But always try to make this relevant to the 

clinical context...

M57. Scaly areas, persistent, face, neck,?DLE 

RAC3247

Mounds of parakeratosis (with neutrophils) 

Perifollicular spongiosis (mild) 

Psoriasiform (mild) 

Sparse dermal infiltrate 

Favour chronic eczematous dermatitis 

PAS stripsx3 to r/o fungal hyphae 

Not suggestive of DLE 

Could this be… 

Seborrhoeic dermatitis 

Fungal (dermatophyte) infection 

RAC3247

Seborrhoeic Dermatitis 

• Common (1-2% 

population) 

• M>F 

• Infants, adults 

• “Seborrhoeic areas” 

– scalp, forehead, 

eyebrows, eyelids, ears, 

cheeks, pre-sternal, 

interscapular

Seborrhoeic Dermatitis 2 

• Sharply circumscribed 

dull red or yellowish 

• Greasy scale 

• Association: AIDS 

• ?related to Malassezia 

furfur (Pityrosporum 

ovale) colonisation

Seborrhoeic Dermatitis 

• Often subtle / non-specific / difficult 

• Infundibular and perifollicular spongiosis 

• Mounds of parakeratosis at the lips of follicular 

ostia with neutrophils 

• Fungal Yeasts / Spores common (no hyphae) 

• Dermal oedema, vascular dilation 

• Mixed superficial perivascular infiltrate 

lymphocytes, histiocytes +/- few eosinophils

M63. Two year hx itchy rash. Improving on topical 

steroids. FH of psoriasis. ?psoriasis ?eczema. 

RAC3257

RAC3257

RAC3257

RAC3257

Multiple levels examined 

Serum extravasate within mounds of parakeratosis 

A small collection of subcorneal neutrophils 

Mild to moderate acanthosis 

Mild patchy spongiosis 

Exocytosis of lymphocytes 

Mild superficial perivascular lymphocytic infiltrate 

Occasional eosinophils 

Confusing overlap features 

Cannot definitely exclude psoriasis 

BUT most of the features fit best with a spongiotic 

dermatitis and the presence of eosinophils would raise 

the possibility of a drug reaction 

Suggest discussion at MDT! 

RAC3257

Follow-Up 

• Joint dermatology review favoured 

autoeczematisation (id reaction) to stasis 

dermatitis / eczema 

• BUT…... 

– Patch testing positive for chromium, cobalt and nickel 

– He works with metals as a grinder and assembler 

Final Diagnosis 

CONTACT DERMATITIS

Contact Dermatitis 

Suggested by history, distribution & enquiry 

occupational exposure 

• Allergic (eosinophils) 

– Cell mediated 

hypersensitivity 

reaction 

– Metals, synthetic 

rubber, 

plants/vegetation, 

topical medicines 

– Patch testing 

• Irritant (neutrophils) 

– More common 

– Physical/chemical 

damage 

– Acute: potent irritant 

e.g. Acid/alkali 

– Chroinic: cummulative 

effect of mild irritant 

e.g. soap

Learning Points: Report Style 

• Consise description 

– Pattern and cells 

– Specific features top to bottom 

• Special stains 

– List and results 

• Offer suggestions in order of probability 

• Suggest clinicopathological correlation 

• Clinical investigations or follow-up often clinch 

the final diagnosis

Other Conditions with 

• Pityriasis rosea 

• Erythema annulare 

centrifugum 

• Superficial fungal 

infection 

(dermatophytosis) 

• Bullous 

pemphigoid/Herpes 

gestationis (early) 

• Pruritic urticarial papules 

and plaques of 

pregnancy 

Spongiosis 

• Erthema multiforme 

• Miliaria rubra 

• Guttate parapsoriasis 

• Acral papular eruption of 

childhood 

• Lichen striatus 

• Insect-bite reaction 

• Prurigo nodularis 

• Grover’s Disease 

• Mycosis fungoides 

• Psoriasis

F58. Groin. ?Herpes 

RAC3185

Layered parakeratosis with neutrophils 

Superficial perivascular lymphocytes 

RAC3185

Serum++ in parakeratosis 

DD: Eczematous dermatosis? 

Psoriasis? 

Fungal?

Diagnosis 

Dermatophytosis 

PAS


• Dermatophytosis may perfectly mimic 

eczematous dermatoses and 

psoriasis (of all sub-types) 

• “Sandwich sign” (layered 

orthokeratosis and parakeratosis) 

clue to fungal infections & psoriasis 

• PAS strips x3 and look hard 

• Negative stains still does not r/o

Spongiotic: Variants 

1. Eosinophilic spongiosis 

2. Neutrophilic spongiosis 

3. Milarial (acrosyringeal) 

4. Follicular spongiosis 

5. Haphazard spongiosis 

Long list!

Eosinophilic Spongiosis 

• Insect bites 

• Allergic Eczemas 

– contact dermatitis 

– Atopic eczema 

– Photoallergic 

• Pemphigus vulgaris 

• Bullous pemphigoid 

• Pemphigoid gestationis 

– Linear IgA 

• Pruritic urticarial papules 

and plaques of pregnancy 

• Incontinential pigmenti 

(vesicular stage) 

• Drug reactions

F80. Urticated blistering eruption, widespread, arms, 

trunk and lesser extent legs ?Bullous Pemphigoid? 

RAC3252

c/w Bullous Pemphigoid BUT: IMF inconclusive 

Histological Pattern NOT specific

Neutrophilic Spongiosis 

• Irritant contact 


• Psoriasis 

• IgA pemphigus 

• Insect bites (flea) 

• Drug reactions 

(AGEP) 

• Prurigo pigmentosa 

• DH, Linear IgA 

• Inflammatory EBA 

• Bullous pemphigoid 

• Pemphigus Vulgaris

Psoriasiform Pattern 

Burton Dassett, South Warwickshire 

83

• PROBLEM 

• Psoriasis (Reiter’s) 

• Mucocutaneous 

candidiasis 

• Mycosis fungoides 

• Chronic eczema 

PSORIASIFORM 

– Many diseases in the category may lack 

psoriasiform pattern at some stage 

– e.g. psoriasis in genital skin 

• Pityriasis rubra pilaris 

• Syphilis (plasma cells) 

• Deficiency States (e.g. Zinc) 

• Chronic scaly superficial 

dermatitis 

• And many more!!!!

F38. Site not known. Rash started on legs and feet in June. 

Disciform, scaly, widespread, itches. More confluent areas on 

feet. No FH psoriasis. ?psoriasis. 

Moderate fairly regular acanthosis 

Focal fusion of rete ridges 

Supra-papillary plate not thinned 

Dermal papillae not long 

Dermal papillae slightly club shaped at tip 

RAC3250

Layered parakeratosis 

Increased & mitotically active basal zone 

Dilated capillary loops 

RAC3250

Absent granular 

Neutrophils in parakeratosis (Munro 

microabscesses) 

Mild spongiosis, minimal excocytosis 

No serum exudate 

Dilated capillary loops 

No fungal hyphae (PAS) 

Diagnosis 

c/w Plaque psoriasis 

RAC3250

F57. Trunk. Generalised pustular rash shortly after 

starting prednisolone for arthralgia 

Confluent parakeratosis 

Absent granular layer 

Upper epidermal pallor 

Mild acanthosis 


Oedematous dermal papillae 

RAC2842

Neutrophils in parakeratosis 

Ascending neutrophils above dermal papillae 

“squirting dermal papillae” 

Diagnosis 

c/w 

Acute generalised psoriasis 

Precipitated by steroids and evolved into typical 

pustular psoriasis clinically

Generalised (eruptive / pustular) 

• Acute onset over 2-3 

days 

• Sterile pustules 

• Trunk and extremities 

• Fever, weight loss 

Psoriasis

Subcorneal 

Pustule 


• Candidiasis 

• Impetigo 

• Suppurative 

infundibulitis 

• Pemphigus foliaceus 

• IgA Pemphigus 

• Subcorneal pustular 

dermatosis 

• Pustular psoriasis 

• Reiter’s syndrome 

• Prurigo pigmentosa 

• Drug reaction (Toxic 

pustuloderma, AGEP)

F61. Hip. Small areas of itchy red erythema, Coeliac 

disease (Gluten free diet since 1977). ?eczema, ?DH, 

?psoriasis 







RAC2576







RAC2576

Not suggestive or eczematous or DH 

Diagnosis 

c/w 

Early (Guttate) Psoriasis 

Consider Nutritional (Coeliac) 

RAC2576

Guttate 

Psoriasis 

c/o Dr Alison Bedlow 

• Eruptive 

• Small (0.5 to 1.5cm) 

• Papules 

• Trunk, proximal 

extremities 

• Younger age 

RAC4199

Psoriasis Early 

• Parakeratotic mounds 

• Loss of granular layer 

• Pallor & vacuolation upper epidermis 

• Migration of neutrophils from capillaries to stratum 

corneum (“squirting papilae”) 

• Lymphocytes is basal epidermis with spongiosis 

• Mitotically active basal zone 

• Mild soriasiform epidermal hyperplasia 

• Tortuous, dilated, congested papilary dermal 

capillaries 

• Oedema 

• Perivascular lymphocytes

M51. No history available. Biopsy from the palm. 

RAC2388

Layered parakeratosis 


Marked psoriasiform acanthosis 

Mild spongiosis 



RAC2388

Neutrophils within parakeratosis 

Moderate spongiosis 

Scant serum exudate 

Diagnosis 

c/w 

Acral psoriasis 

RAC2388

Psoriasis v’s Eczematous 

Acral / volar skin psoriasis 

CLUE 

• Exclude fungi (PAS) 

• Mounds of scalecrusts 

staggered 

throughout a 

thickened cornified 

layer or neutrophils 

in scale-crusts 

= PSORIASIS 

– Ackerman 3 rd Edn. Derm101.com

M35. Foreskin (circumcision). Clinically BXO. 

RAC2963

RAC2963

Striking parakeratosis housing neutrophils 


Marked psoriasiform acanthosis 



Dilated capillary vessels 

Differential Diagnosis 

c/w 

1. Psoriasis (or Reiter’s syndrome) 

2. Chronic hyperplastic mucosal candidiasis 

PAS stain… 

RAC2963

Diagnosis 

Chronic hyperplastic mucocutaneous 

candidiasis 

Dermatophytoses and mucocutaneous 

candidiasis can perfectly mimic psoriasis 

Hyphae may be sparse (look carefully)


• Do not rely upon the clinical history or suggested 

diagnosis 

• BUT be particularly wary of non-expert 

dermatologists!!! 

• Lower your threshold for PAS stain on 

mucocutanous sites 

• Candida may colonise (no neutrophils) or 

superinfect (neutrophils) leucoplakia and 

lichenoid dermatoses at mucocutaneous sites 

(but the underlying condition should be present)

Psoriasis: Differential Diagnosis 

• Dermatophytosis & Candidasis 


• Lichen simplex chronicus 

• Papulosqumous drug eruption 

– Similar but moderate numbers of 

eosinophils (if in doubt raise possibility) 

• Seborrhoeic dermatitis 

• Mycosis fungoides

M55. Widespread rash, papules and plaques 

Slight hyperkeratosis (follicular accentuation) 

Slight upper epidermal pallor 

Moderate psoriasiform acanthosis 

Suprapapillary plate not thinned 

Broad rete ridges 

Narrow dermal papillae 

RAC2309

Focal parakeratosis 

Intact granular layer 

Absent neutrophils 

RAC2309

Diagnosis 

c/w 

Pityriasis rubra pilaris 

Rarely seen in Warwick and usually would 

be a clinical diagnosis!

Pityriasis Rubra Pilaris 

• Burning/pruritis 

• Follicular 

hyperkeratosis 

• Erthematous 

perifollicular lesions 

with 

• Scale 

– Face/Salp Powdery 

– Body: Course 

– +/- Ichthyosiform

Pityriasis 

Rubra Pilaris 

• Coalesce and commonly 

progressing to 

erythroderma (islands of 

sparing) 

• Palmoplantar 

hyperkeratosis 

– Marked, yellow-orange hue 

• Pityriasis capitis +/- 

alopecia 

• Nail Changes

PRP: Follicular Papules 

• Conical hyperkeratosis in follicular ostia 

• Adjacent hyperkeratosis 

• Foci of parafollicular parakeratosis 

• Uniform acanthosis with broad rete 

• Mild to Moderate perivascular lymphocytic 

dermal infiltrate

PRP: Establised Lesions 

• May be non-specific 

• “Spotty” parakeratosis* 

– Vertical and Horizontal planes 

• Focal or confluent hypergranulosis* 

• Thick suprapapillary plates, 

• Broad acanthotic rete, narrow dermal papillae 

• Dilated but not tortuous capillaries* 

• +/- Mild spongiosis with lyphocytes 

• No neutrophils* (unless infection) 

– Acantholysis +/- dyskeratosis 

• Mild to moderate perivascular lymphocytic +/- 

a few plasma cells and eosinophils

M65. Ankle. Chronic liver disease. ? Bullous 

dermatosis ?Vitamin/mineral deficiency rash 

RAC3255

Regular acanthosis 


Loss of granular layer 

RAC3255

“Marked hyper- and parakeratosis with full thickness dysplasia 

of the epidermis amounting to intraepidermal 

carcinoma. Some extravasated red cells are noted in the 

dermis at the centre of the biopsy, but this is relatively limited. 

No hair follicles are included in the biopsy. There are no 

features here specific for vitamin C deficiency.“ 

“Reviewed at MDT. Known zinc deficiency. Patient has 

responded to zinc supplements” 

Final Diagnosis 

Zinc Deficiency 

(Acrokeratosis enteropathica) 

RAC3255

Acrodermatitis Enteropathica 

(Zinc Deficiency) 

Bowen et al , University of Utah 

Department of Dermatology 

ww.bweems.com/acroent.html

Acrodermatitis Enteropathica 

(Zinc Deficiency) 

Bowen et al , University of Utah 

Department of Dermatology 

ww.bweems.com/acroent.html 

Pale keratinocytes in upper 1/3 

Keratinocytes are much larger than normal.

Epidermal Pallor • Maceration 

• Re-epithelialisation 

• Nutritional 

– Zn Deficiency 

– Pellagra 

• Necrolytic migratory 

erythema 

• Psoriasis & Reiter’s 

• Irrititant contact 

dermatitis 


• Syphilis, secondary 

• Photoxic dermatitis 

• Pityriasis lichenoides 

acuta

Necrolytic Migratory 

Erythema 

Rev. Hosp. Clin. vol.56 no.6 

NECROLYTIC MIGRATORY 

ERYTHEMA ASSOCIATED WITH 

GLUCAGONOMA SYNDROME: A 

CASE REPORT 

Dal Coleto et al 

Examination of biopsy specimens 

showed an intraepidermal cleft, 

presence of vacuolated pale 

epidermal cells with pyknotic nuclei, 

and neutrophils in the upper 

epidermis (Fig. 2)—all changes 

consistent with NME. 

RAC

Summary of Approach 

• Knowledge of clinical dermatology 

• Adequate clinical information 

– Clinical differential diagnosis 

– Clinical images 

• Appropriate biopsy type, lesion, fixation 

– IMF?, EM?, Frozen Sections?, Molecular? 

• Systematic approach to slides 

– Top to bottom 

– Algorithmic & Clues 

– Levels & specials 

– Weighted differential diagnosis 

• Clinicopathological conference 

– Repeat biopsy? 

122

Thank-You 

• Dr Phillip Mckee 

• Dr Eduardo Calonje 

• Dr Scott Sanders 

• Dr Saleem Taibjee 

• Dr Alison Bedlow 

• Dr Frances Humphreys 

• Dr Robert Charles- 

Holmes 

• Dr Bruce Gee 

• All lab & derm teams 

Warwick

• Don’t need to ink 

inflammatory cases 

• Narrow incision 

embed on edge, 

levels 

• Wide incision, bisect 

longitudinally, no 

levels 

• But do NOT cut intact 

blisters 

Cut-Up

• PAS for fungi 

Special Stains 

• Gram (Brown Brenn) for bacteria 

– Suppuration 

• Zn for AFB 

– Caeseating or Pustulating granulomas 

– Extensive tuberculoid granulomas 

• Congo red for “systemic” amyloid 

• Tol. Blue, Giemsa 

– Mast cells 

• Chloroacetate esterase 

– Mast cells, granulocytic leukaemia

When to Do PAS 

• Clinical suspicion 

• Spongiotic 

• Psoriasiform 

• Mucocutaneous (including lichenoid) 

• Neutrophils in cornified layer 

• Invisible dermatosis (tinea) 

• Pustulating granulomas 

• ?Lupus, dermatomyositis, Lichen Sclerosus 

– Basemement membrane

Immunos 

• Pan-keratin for macular amyloid 

• HHV8 for Kaposi’s sarcoma Lymphoid 

panels for lymphomas 

• CD117 for mastocytosis 

• CD1a for Langerhan’s cell histiocytosis 

• CD30 for lymphomatoid papulosis 

• Mycosis fungoides

Tips for FRCPath 

• Describe skin from top to bottom 

• Look at whole section 

• Site relevant 

• Dual Pathology

Tips 

• Artefacts may dominate appearances 

• Do NOT commit to diagnosis on initial biopsy if 

evidence insufficient 

• Ask for another (bigger) biopsy 

• Dermatologist usually right BUT NOT ALWAYS 

• Don’t be afraid to make other suggestions but try 

to think clinically 

• If a definitive diagnosis is not possible offer 

suggestions weighting the differential diagnostic 

possibilities

Dr Richard Carr

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