Diagnostic clues

Features of particular processes20



Signs of photosensitivity20


Signs of rubbing/scratching20


Subtle clues to drug reactions20


Clues to elastic tissue alterations20


Clues to deficiency states21


Clues to fungal infections21


Subtle clues to a folliculitis21


‘Last week’s sign’22


Lagging histology22




Histological features – what do they suggest?22


Superficial and deep inflammation22


A ‘busy’ dermis22


Absent stratum corneum23


Filled papillary dermis23


Papillary microabscesses23


Sparse perivascular neutrophils23


Thickened basement membrane23


Mid-dermal infiltrate and mucin24


Epidermotropism and exocytosis24


The epidermal/follicular ‘vacuum cleaner’24


Parakeratosis as a helpful sign25


Parakeratotic follicular lipping25


‘Chunks of coal’25


Interstitial eosinophils25


‘Bottom-heavy’ infiltrates26


The ‘bare underbelly’ sign26


Intraluminal giant cells/histiocytes26


Intravascular leukocytes26


High apoptotic (dyskeratotic) keratinocytes26


Vertical collagen bundles27


Loose pink fibrillary collagen27


Extravasated erythrocytes27


Pallor of epidermal cells27


Clear cell tumors27


Granular cell tumors28


Plexiform tumors28


Tumors with hemosiderin28


Clues to a particular disease29


Clues to herpes folliculitis29


Clues to Grover’s disease29


Clues to pityriasis rubra pilaris29


Clues to cicatricial pemphigoid29


Clues to epidermolysis bullosa acquisita29


Clues to mycosis fungoides29


Clues to alopecia areata30


Clues to androgenetic alopecia30


Late bullous lesions30


Granuloma annulare versus necrobiosis lipoidica30


Granuloma annulare versus lichen nitidus30


Clues to trichoepithelioma (over BCC)30


Clue to angiosarcoma30


Clues to Kaposi’s sarcoma30


Clues to bacillary angiomatosis30


Clues to amyloidosis30


Paraneoplastic dermatoses30


General helpful hints and cautions31


Beware of keratoacanthoma simulants31


Be cautious with amyloid stains31


‘Up it half a grade’31


‘Do serials, not deepers’31


Fungi may be missed on PAS stain31


Dermal neutrophils – often forgotten31


Itching ankles31


The demonstration of cryptococci32


The edge of Bowen’s disease32


False negative immunoperoxidase32


Miscellaneous hints32





FEATURES OF PARTICULAR PROCESSES



SIGNS OF PHOTOSENSITIVITY(Fig. 2.1)





• Dilated vessels in the upper dermis


• Stellate fibroblasts/dendrocytes


• Deep elastotic fibers


• Deep extension of the infiltrate


• Epidermal ‘sunburn’ cells.










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B9780702034855000036/gr1b.jpg is missing
Fig. 2.1
Photosensitivity reaction. (A) Note the mild telangiectasia, scattered stellate cells, deep extension of the infiltrate and mild deep solar elastosis. (B) Note the stellate cells. (H & E)


Note: The duration of the process and the underlying nature of the light reaction will influence the response. Only one or two features may be present, e.g. sunburn cells (apoptotic keratinocytes) are confined to phototoxic and photosensitive drug eruptions.


SIGNS OF RUBBING/SCRATCHING(Fig. 2.2)










Acute, severe: Pale pink epidermis, sometimes with loss of cell borders; pin-point erosions or larger ulcers; fibrin below the epidermis.
Chronic, persistent: Psoriasiform epidermal hyperplasia; vertical streaks of collagen in the papillary dermis; stellate fibroblasts/dendrocytes; fibroplasia of varying amounts; enlarged follicular infundibula (as prurigo nodularis commences); compact orthokeratosis.








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Fig. 2.2
Chronic rubbing leading to vertical collagen in the papillary dermis and psoriasiform hyperplasia of the epidermis. (H & E)



SUBTLE CLUES TO DRUG REACTIONS





• Superficial dermal edema


• Activated lymphocytes


• Eosinophils and/or plasma cells


• Red cell extravasation


• Endothelial swelling of vessels


• Exocytosis of lymphocytes


• Apoptotic keratinocytes.

The changes present will mirror the clinical types of reaction. In morbilliform reactions, lymphocytes extend into the lower epidermis and the apoptotic keratinocytes are in the basal layer.


CLUES TO ELASTIC TISSUE ALTERATIONS





• Small blue coiled/clumped fibers (pseudoxanthoma elasticum)


• Wavy epidermis (particularly in children)


• Elastophagocytosis


• Dispersed neutrophils (early cutis laxa)


• Unusually thickened collagen (connective tissue nevus).



CLUES TO FUNGAL INFECTIONS(Fig. 2.3)


Basically, these features should prompt the performance of a PAS stain. Many simulants exist.








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Fig. 2.3
Dermatophyte. The fungal elements are present in the region with compact orthokeratosis. Note the adjacent normal ‘basket-weave’ pattern. (H & E)





• Compact orthokeratosis with no other explanation


• Layering of epidermal cornification (‘sandwich sign’)


• Neutrophils in the epidermis/stratum corneum


• Spongiosis, particularly palmoplantar


• Suppurative folliculitis.


SUBTLE CLUES TO A FOLLICULITIS(Fig. 2.4)


These signs refer to a likely folliculitis at deeper levels of the biopsy.








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Fig. 2.4
Folliculitis. There is deep dermal inflammation and an ‘uneven vasculitis’ more superficially. A ruptured and inflamed follicle was present on deeper levels. (H & E)





• Neutrophils on top of the stratum corneum


• Neutrophils at the edge of the tissue section



• Focal splaying of neutrophils and dust in mid dermis.


‘LAST WEEK’S SIGN’(Fig. 2.5)


This refers to a dermatosis, no longer active, which is ‘playing itself out’. It was presumably more active some days earlier.








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Fig. 2.5
‘Last week’s sign’. The return to the production of normal basket-weave keratin beneath a layer of parakeratosis suggests there is little ongoing activity in this region. (H & E)





• Parakeratosis overlying basket-weave orthokeratin (the key feature)


• Mild hyperplasia of the epidermis


• Mild dermal inflammation.


LAGGING HISTOLOGY


This refers to several conditions in which the clinical appearances may be striking in comparison to the histology.




• Sclerodermoid GVHD may have ‘rock-hard skin’, but only subtle collagen deposition.


• Cicatricial alopecia can be similar.


• Urticaria – histology underestimates the edema because of dehydration during tissue processing.


• Prurigo nodularis – there may be clinical nodules but no histological swollen infundibula, only psoriasiform hyperplasia of lichen simplex chronicus.


• Pauci-cellular photodermatoses – there may be striking clinical changes but only telangiectasia and sparse inflammatory cells on histology.


HISTOLOGICAL FEATURES – WHAT DO THEY SUGGEST?



SUPERFICIAL AND DEEP INFLAMMATION(Fig. 2.6)


The presence of a superficial and deep inflammatory cell infiltrate within the dermis should trigger the mnemonic ‘8Ls + DRUGS’.








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Fig. 2.6
A superficial and deep dermal infiltrate. This is one of the ‘L’ diseases – polymorphiclight eruption. (H & E)










8Ls Drugs



• Light reactions


• Lymphoma


• Leprosy


• Lues


• Lichen striatus


• Lupus erythematosus


• Lipoidica (necrobiosis)


• Lepidoptera (and other arthropods)



• Dermatophyte


• Reticular erythematous mucinosis


• Urticarial stages (bullous pemphigoid)


• Gyrate erythemas


• Scleroderma (localized)


• And, of course, drug reactions


A ‘BUSY’ DERMIS(Fig. 2.7)


‘Busy’ refers to a dermis that appears focally hypercellular on scanning magnification and is not usually due to the usual inflammatory infiltrates.








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Fig. 2.7
A ‘busy’ dermis. There is hypercellularity in this case of interstitial granulomatous drug reaction. (H & E)





• Incomplete form of granuloma annulare


• Interstitial granulomatous dermatitis


• Interstitial granulomatous drug reaction


• Resolving vasculitis (increased mucin also)


• Chronic photodermatoses


• Folliculitis – at deeper levels (cells are neutrophils and dust)



• Desmoplastic melanoma (also perivascular lymphocytes)


• Kaposi’s sarcoma (early stage).


ABSENT STRATUM CORNEUM





• Staphylococcal scalded skin syndrome


• Pemphigus foliaceus


• Peeling skin syndrome


• Psoriatic erythroderma (psoriasiform hyperplasia present)


• Artifacts.


FILLED PAPILLARY DERMIS(Fig. 2.8)


The low power impression is that of a variably hypercellular papillary dermis. Excluded from consideration are nodular and diffuse infiltrates also involving the reticular dermis. The ‘LUMP’ mnemonic covers most cases: lichenoid, urticaria pigmentosa, mycosis fungoides, pigmented purpuric dermatoses. Expressed differently they are:


• Most of the lichenoid tissue reactions


• Pigmented purpuric dermatoses


• Cutaneous T-cell lymphoma


• Parapsoriasis (if not included above)


• Some mastocytomas


• Early lichen sclerosus et atrophicus.








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Fig. 2.8
The papillary dermis is filled. This is mastocytosis. (H & E)



PAPILLARY MICROABSCESSES(Fig. 2.9)





• Dermatitis herpetiformis


• Linear IgA disease


• Cicatricial pemphigoid


• Localized cicatricial pemphigoid


• Bullous lupus erythematosus


• Epidermolysis bullosa acquisita


• Drugs


• Hypersensitivity vasculitis (rare)


• Rheumatoid neutrophilic dermatosis


• Pemphigoid gestationis (eosinophils)

Aug 24, 2016 | Posted by in Dermatology | Comments Off on Diagnostic clues
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