Dermatitis

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Author: Mikael Häggström [notes 1]
Scope: This article deals with skin conditions where inflammation is the main finding, excluding suspected malignant skin excisions (where inflammation is often a concurrent finding).

Sampling

  • For punch biopsies, a size of 4 mm is preferred for most inflammatory dermatoses.[1]
  • Panniculitis or cutaneous lymphoproliferative disorders: 6 mm punch biopsy or skin excision.[1]

A superficial or shave biopsy is regarded as insufficient.[1]

Fixation

Generally 10% neutral buffered formalin.

See also: General notes on fixation

Gross processing

Gross pathology processing of skin lesions with benign appearance, by lesion size:[4]
<4 mm 4 - 8 mm 9 - 15 mm

Tissue selection from skin excision with lesion less than 4 mm with benign appearance.png

Tissue selection from skin excision with lesion 4-8 mm with benign appearance.png

Tissue selection from skin excision with lesion 9-15 mm with benign appearance.png

In table above, each top image shows recommended lines for cutting out slices to be submitted for further processing. Bottom image shows which side of the slice that should be put to microtomy. Dashed lines here mean that either side could be used.

Further information: Gross processing of skin excisions

Staining

3 H&E sections and one section with periodic acid Schiff (PAS)[notes 2][1]

  • If suspected bacterial and fungal microorganisms, consider Gram stain and Gomori methenamine silver stain.[1]

Microscopic evaluation

One approach is to classify into mainly either of the following, primarily based on depth of involvement:[1]

  • Epidermis, papillary dermis, and superficial vascular plexus:
  • Vesiculobullous lesions
  • Pustular dermatosis
  • Non vesicullobullous, non-pustular
  • With epidermal changes
  • Without epidermal changes. These characteristically have a superficial perivascular inflammatory infiltrate, and can be classified by type of cell infiltrate:[1]
  • Lymphocytic (most common)
  • Lymphoeosinophilic
  • Lymphoplasmacytic
  • Mast cell
  • Lymphohistiocytic
  • Neutrophilic

Continue in corresponding section:

Non vesicullobullous, non-pustular lesions with epidermal changes

Spongiotic dermatitis

It is characterized by epithelial intercellular edema.[1]

Characteristics Micrograph Photograph
Acute Subacute Chronic
Generally/Not otherwise specified[notes 3] Typical findings:[1]
  • Variable degree of epidermal spongiosis and vesicle formation, filled with proteinaceous fluid containing lymphocytes and histiocytes.
  • Usually superficial dermal edema with perivascular lymphocytic infiltrate, with exocytosis.
  • No acanthosis or parakeratosis.
Typical findings:[1]
  • Mild to moderate spongiosis and exocytosis of inflammatory cells
  • Irregular acanthosis and parakeratosis.
  • Superficial dermal perivascular lymphohistiocytic infiltrate
  • Swelling of endothelial cells
  • Papillary dermal edema are present
Typical findings:[1]
  • The spongiosis is mild to absent
  • Pronounced irregular acanthosis, hyperkeratosis, and parakeratosis
  • Minimal dermal inflammation and exocytosis of inflammatory cells are present.
  • Possibly fibrosis of papillary dermis

PAS stain is essential to exclude fungal infection.[1]

Micrograph of subacute spongiotic dermatitis.jpg Subacute
Allergic/contact dermatitis or atopic dermatitis As above. Eosinophils may be present in the dermis and epidermis (eosinophilic spongiosis).[1] Spongiotic dermatitis from drug allergy.jpg Allergic dermatitis Eczema (14100950936).jpg Atopic dermatitis
Seborrheic dermatitis Typical findings:[5]
  • Focal, usually mild, spongiosis with overlying scale crust, with a few neutrophils
  • The crust is often centered on a follicle
  • The papillary dermis is generally mildly edematous
  • Dilated blood vessels in the superficial vascular plexus
  • Mild superficial perivascular infiltrate of lymphocytes, histiocytes and occasional neutrophils. There is some exocytosis of inflammatory cells but not as prominent as in nummular dermatitis
Typical findings:[5]
  • Psoriasiform hyperplasia, initially slight, with mild spongiosis
  • Usually numerous yeast-like organisms in the surface keratin
  • Same changes as seen in acute stage.
Typical findings:[5]
  • More pronounced psoriasiform hyperplasia
  • Only minimal spongiosis
  • Presence of scaling crusts in a folliculocentric distribution, distinguishes from psoriasis.
Seborrhoeic dermatitis example.jpg

In addition to above, an unspecific spongiotic dermatitis can be consistent with nummular dermatitis, dyshidrotic dermatitis, Id reaction, dermatophytosis, miliaria, Gianotti-Crosti syndrome and pityriasis rosea.[1][notes 3]

Interface dermatitis

These are sorted into either:[1]

  • Interface dermatitis with vacuolar change
  • Interface dermatitis with lichenoid inflammation
Interface dermatitis with vacuolar change
Causes of vacuolar interface dermatitis edit
Main conditions[6] Characteristics Micrograph Photograph
Generally/Not otherwise specified Typical findings, called "vacuolar interface dermatitis":[6]
  • Mild inflammatory cell infiltrate along the dermoepidermal junction (black arrow in image)
  • Vacuolization within the basal keratinocytes (white arrow in image)
  • Often necrotic, predominantly basal, individual keratinocytes, manifesting as colloid or Civatte bodies
Vacuolar interface dermatitis, annotated.jpg
Acute graft-versus-host-disease
  • Vacuolar alteration of various severity, from focal or diffuse vacuolation of the basal keratinocytes (grade I), to separation at the dermoepidermal junction (grade III)
  • Involvement of the hair follicle[6]
  • Rarely eosinophils[6]
Micrographs of grades of skin graft-versus-host-disease.jpg
Allergic drug reaction
  • Rarely involvement of hair follicles.[6]
  • Frequently eosinophils[6]
Spongiotic dermatitis from drug allergy.jpg
Lichen sclerosus Hyperkeratosis, atrophic epidermis, sclerosis of dermis and dermal lymphocytes.[7] Micrograph of lichen sclerosus.jpg
Erythema multiforme
Lupus erythematosis Typical findings in systemic lupus erythematosus:[8]
  • Fibrinoid necrosis at the dermoepidermal junction
  • Liquefactive degeneration and atrophy of the epidermis
  • Mucin deposition in the reticular dermis
  • Edema, small hemorrhages
  • Mild and mainly lymphocytic infiltrate in the upper dermis
  • Fibrinoid material in the dermis around capillary blood vessels, on collagen and in the interstitium
  • In non-bullous cases, perivascular and interstitial neutrophils are sometimes present in the upper dermis, with damage to blood vessels
Histopathology of systemic lupus erythematosus.jpg Butterfly rash of lupus erythematosus.jpg

An interface dermatitis with vacuolar alteration, not otherwise specified, may be caused by viral exanthems, phototoxic dermatitis, acute radiation dermatitis, erythema dyschromicum perstans, lupus erythematosus and dermatomyositis.[1]


Further information: Vacuolar interface dermatitis
Interface dermatitis with lichenoid inflammation
Main conditions[1] Characteristics Micrograph Photograph
Generally/Not otherwise specified Typical findings:[1]
  • In the papillary dermis: a confluent, band-like, dense inflammation of mainly small lymphocytes and a few histiocytes, along or hugging the dermoepidermal junction.
  • Often vacuolar degeneration of basal keratinocytes and apoptotic bodies (colloid or Civatte bodies).
Lichen planus Irregular epidermal hyperplasia with a jagged “sawtooth” appearance, compact hyperkeratosis or orthokeratosis, foci of wedge-shaped hypergranulosis, basilar vacuolar degeneration, slight spongiosis in the spinous layer, and squamatization. The dermal papillae between the elongated rete ridges are frequently dome shaped. Necrotic keratinocytes can be observed in the basal layer of the epidermis and at the dermal-epidermal junction. Eosinophilic remnants of anucleate apoptotic basal cells may also be found in the dermis and are referred to as “colloid or civatte bodies”. Whickham striae are usually seen in the areas of hypergranulosis. Vacuolar degeneration at the basal layer may be noted leading to focal subepidermal clefts (Max Joseph spaces). Squamatization occurs as a result of maturation and flattening of cells in the basal layer. It happens in areas of marked hypergranulosis with prominence of the sawtooth pattern of rete ridges. Wedge-shaped hypergranulosis can occur in the eccrine ducts (acrosyringia) or hair follicles (acrotrichia). In the hypertrophic subtype, the associated hyperkeratosis, parakeratosis, hypergranulosis, papillomatosis, acanthosis, and hyperplasia markedly increased with thicker collagen bundles forming in the dermis. Moreover, the rete ridges are more elongated and rounded as opposed to the typical sawtooth pattern. In atrophic LP, loss of the rete ridges and dermal fibrosis is prominent. In vesiculobullous LP, the disease progression is quicker. Hence, some of the distinctive features such as hyperkeratosis, hypergranulosis, or dense lymphocytic dermal-epidermal infiltrate may not be present. LP lesion may resolve with residual hyperpigmentation caused by a persistent increase in the number of melanophages in the papillary dermis.[9] Histopathology of lichen planus.jpg Lichen planus 1.jpg
Lichenoid drug reaction

Can virtually be indistinguishable from cutaneous LP both clinically and histopathologically.

  • Typically, lesions have a photodistribution in the absence of oral mucosal involvement.[9]
  • Characteristically parakeratosis, a dermal eosinophilic infiltrate, and a perivascular lymphocytic infiltrate affecting the reticular dermis.
  • Epidermal changes are less common in lichenoid drug eruptions when compared to classic lichen planus. However, a higher concentration of necrotic keratinocyte and eosinophils in the infiltrate can be helpful in distinguishing lichenoid drug reaction from cutaneous lichen planus. A lengthy interval between the commencement of drug therapy and the onset of lesions does not exclude a diagnosis of lichenoid drug reaction. Resolution of the lesions often occurs within weeks to months after discontinuation of the offending drug.[9]
Histopathology of lichenoid drug reaction.jpg
Lichen nitidus
  • Localized granulomatous lymphohistiocytic infiltrate in an expanded dermal papilla
  • Thinning of overlying epidermis and downward extension of the rete ridges at the lateral margin of the infiltrate, resulting in a typical "claw clutching a ball" appearance.[10]
Histopathology of lichen nitidus.jpg Photography of lichen nitidus.jpg
Lichen amyloidosus Presence of amyloid, possibly with direct immunofluorescence and Congo red staining.[11]
Congo red.

Interface dermatitis with lichenoid inflammation, not otherwise specified, can be caused by lichen planus-like keratosis, lichenoid actinic keratosis, lichenoid lupus erythematosus, lichenoid GVHD (chronic GVHD), pigmented purpuric dermatosis, pityriasis rosea, and pityriasis lichenoides chronica.[1] Unusual conditions that can be associated with a lichenoid inflammatory cell infiltrate are HIV dermatitis, syphilis, mycosis fungoides, urticaria pigmentosa, and post-inflammatory hyperpigmentation.[1] In cases of post-inflammatory hyperpigmentation, it is important to exclude potentially harmful mimics such as a regressed melanocytic lesion or lichenoid pigmented actinic keratosis.[1]

Psoriaform dermatitis

Examining multiple deeper levels is recommended if initial cuts do not correlate well with the clinical history.[1]

Psoriaform dermatitis typically displays:[1]

  • Regular epidermal hyperplasia, elongation of the rete ridges, hyperkeratosis, and parakeratosis.
  • Usually:A superficial perivascular inflammatory infiltrate
  • Often: Thinning of epidermal cells overlying the tips of dermal papillae (suprapapillary plates), and dilated, tortuous blood vessels within these papillae

Further histopathologic diagnosis is performed by the following parameters:

Psoriasiform dermatitis[1]
Condition Hyperkeratosis Parakeratosis Acanthosis Suprapapillary plate Granular cell layer changes Spinous cell layer changes Basal cell layer changes Other distinctive feature Micrograph Photograph
Psoriasis Present Diffuse Regular Thin Decreased or absent Increased mitoses; minimal spongiosis
Clubbed rete pegs[12] [13]
Absent
  • Microabscesses
Micrograph of psoriasis vulgaris.jpg Psoriasis on elbow.jpg
Psoriasiform drug reaction Present Focal Regular and irregular Normal or thick Normal Spongiosis; eosinophilic infiltrate Inflammatory cells; Civatte bodies
Chronic allergic/contact and atopic dermatitis Present Focal; crust may be present Irregular Normal or thick Normal Spongiosis; eosinophilic infiltrate Absent
Fungal infection Compact Focal; crust may be present Irregular Normal or thick Normal Occasional neutrophiles; Absent
Lichen simplex chronicus Present Focal; thick crust Regular or irregular Thin or thick Thickened; hypergranulosis ±minimal inflammatory infiltrate Absent
Scabies Present Focal or diffuse Irregular Normal or thick Normal Inflammatory infiltrate; eosinophilic spongiosis Absent
Seborrheic dermatitis and HIV dermatitis Present Focal Irregular Normal or thick Normal Spongiosis; lymphocytic and neutrophilic infiltrate Absent
Pityriasis rubra pilaris Compact Shoulder parakeratosis[notes 4]; alternating orthokeratosis and parakeratosis Regular or irregular Normal or thick Normal Spongiosis; lymphocytic infiltrate; rare acantholysis Occasional vacuolar change
Pityriasis rosea Present Focal Irregular Normal or thick Normal Small foci of spongiosis; lymphocytic infiltrate Occasional necrotic keratinocytes
Syphilis Present Focal Regular or irregular Normal or thick Normal Lymphocytes and neutrophils Interface change
Pityriasis lichenoides chronica Present Caps of parakeratosis Irregular Normal Normal Mild spongiosis, lymphocytic infiltrate; necrotic keratinocytes Necrotic keratinocytes
Mycosis fungoides Present Focal Regular or irregular Normal Normal Minimal or no spongiosis; ±Pautrier microabscess Atypical lymphoid cells lining the dermo–epidermal junction
Pautrier microabscesses

Non vesicullobullous, non-pustular lesions without epidermal changes

Lymphocytic infiltrate

Main conditions[1] Characteristics Micrograph Photograph
Urticaria, lymphocyte predominant Perivascular location. Mast cells are relatively sparse, potentially demonstrated with special stains, preferably tryptase stain. Extravasated erythrocytes are present in about 50% of the cases. No vasculitis.[14] Micrograph of urticaria.jpg Dermal edema [solid arrows in (A,B)] and a sparse superficial predominantly perivascular and interstitial infiltrate of lymphocytes and eosinophils without signs of vasculitis (dashed arrow).[15] Urticaria near navel.jpg
Fungal skin infection Often visible fungus. Other signs depend on fungus species.[16]
Pigmented purpuric dermatosis
  • Perivascular infiltrate, but may involve the dermis, further away from blood vessels.[17]
  • Sometimes tendency for lichenoid infiltrate[notes 5][17]
  • Mild vascular damage, mainly endothelial swelling and focal karyorrhectic debris.[17]
  • Red blood cell extravasation.[17]
  • The epidermis may be normal or may exhibit spongiosis, focal parakeratosis, exocytosis and/or vacuolar change.[17]
Histopathology of Schamberg disease.jpg Schambergdisease-26male.png
Erythema annulare centrifugum
  • Superficial types:[18]
  • Mild spongiosis, parakeratosis and microvesiculation.
  • "Coat-sleeve anomaly": tight lymphohistiocytic infiltrate surrounding superficial vessels

Deep lesions: Sharply demarcated perivascular mononuclear cell infiltrate in middle to deep dermis[18]

Micrograph of erythema annulare centrifugum.jpg Erythema annulare centrifugum on arms and legs.jpg
Not otherwise specified[notes 3] A lesion with superficial lymphocytic infiltrate without additional histopathologic characteristics can be due to for example drug reactions and insect bites.[1][notes 3]

Lymphoeosinophilic infiltrate

Main conditions[1] Characteristics Micrograph Photograph
Urticaria, lymphocyte predominant Perivascular location. Mast cells are relatively sparse, potentially demonstrated with special stains, preferably tryptase stain. Extravasated erythrocytes are present in about 50% of the cases. No vasculitis.[14] Micrograph of urticaria.jpg Dermal edema (solid arrows) and a sparse superficial predominantly perivascular and interstitial infiltrate of lymphocytes and eosinophils (dashed arrow) Urticaria near navel.jpg
Prevesicular stage of bullous pemphigoid Image at right shows influx of inflammatory cells including eosinophils and neutrophils in the dermis (solid arrow) and blister cavity (dashed arrows), and deposition of fibrin (asterisks).[19] However, the diagnosis of bullous pemphigoid consist of at least 2 positive results out of 3 criteria:[20]
  • Pruritus and/or predominant cutaneous blisters
  • Linear IgG and/or C3c deposits (in an n- serrated pattern) by direct immunofluorescence microscopy (DIF)
  • Positive epidermal side staining by indirect immunofluorescence microscopy on human salt-split skin (IIF SSS) on a serum sample.
Micrograph of infiltrate in bullous pemphigoid.jpg
Not otherwise specified[notes 3] A lesion with superficial lymphoeosinophilic infiltrate without additional histopathologic characteristics can be due to for example drug reactions and insect bites.[1][notes 3]

Lymphoplasmacytic infiltrate

Main conditions[1] Characteristics Micrograph Photograph
Rosacea Typically enlarged, dilated capillaries and venules located in the upper dermis, angulated telangiectasias, perivascular and perifollicular lymphocytic infiltration, and superficial dermal edema.[21] Micrograph of rosacea.jpg Rosacea.jpg
Secondary syphilis Various, but often one or a combination of:[22]
  • Psoriasiform hyperplasia with superficial neutrophils
  • Lichenoid tissue reaction, epidermal apoptosis and exocytosis of neutrophils
  • Superficial and deep chronic infiltrate in the dermis
  • Often numerous plasma cells in about 1/3 of cases
  • Often endothelial swelling.
Micrograph of secondary syphilis, HE.jpg Secondary stage syphilis sores (lesions) on the soles of the feet. Plantar lesions-CDC.jpg
Erythema migrans Typically a superficial and deep perivascular lymphocytic infiltrate.[23] Plasma cells are typically located at the periphery of the lesion, whereas eosinophils are in the center.[23] Erythema migrans - erythematous rash in Lyme disease - PHIL 9875.jpg
Kaposi’s sarcoma in patch stage The patch stage typically shows irregular proliferation of jagged vascular channels in the dermis below an integral epidermis. The so-called promontory sign is sometimes found in patch stage lesions and denotes vascular spaces surrounding pre-existing blood (see image).[24]

vessels

Micrograph of promontory sign of kaposi's sarcoma.jpg Patch stage Kaposi's sarcoma.jpg
Not otherwise specified[notes 3] A lesion with superficial lymphoplasmacytic infiltrate without additional histopathologic characteristics can be due to for example trauma, ulceration, scar and early cutaneous connective tissue diseases.[1][notes 3]

Mastocytosis

Main conditions[1] Characteristics Micrograph Photograph
Urticaria pigmentosa Mastocytosis with a clinical picture of darkish spots. Histopathology of urticaria pigmentosa.jpg Urticaria pigmentosa lesions on a child.jpg
Not otherwise specified[notes 3] Includes the rare disease of primary mastocytosis.[1][notes 3]

Lymphohistiocytic infiltrate

Leprosy

These include bacterial infections including leprosy, and the sample should therefore be stained with Ziel-Neelsen, acid fast stains, Gomori methenamine silver, PAS, and Fite stains.[1] If negative, an unspecific lymphohistocytic dermatosis may be caused by drug reactions and viral infections.[1][notes 3]

Neutrophilic infiltrate

Main conditions[1] Characteristics Micrograph Photograph
Urticaria, neutrophil predominant
  • Interstitial location[14]
  • Relatively dense infiltrate[14]
  • Mast cells are relatively sparse, potentially demonstrated with special stains, preferably tryptase stain.[14]
  • Extravasated erythrocytes are present in about 50% of the cases [14]
  • No vasculitis.[14]
Micrograph of neutrophilic urticarial dermatosis.jpg Neutrophilic urticarial dermatosis.jpg
Dermatitis herpetiformis
  • Subepidermal vesicles and blisters associated with accumulation of neutrophils at the papillary tips.[25]
  • Sometimes presence of eosinophils, giving an appearance similar to bullous pemphigoid.[25]
  • The histopathology is unspecific in approximately 35%–40% of the cases,[25] and direct immunofluorescence is needed, showing deposition of IgA in the papillary dermis in a granular or fibrillar pattern.[26]
Micrograph of dermatitis herpetiformis.jpg Dermatitis herpetiformis.jpg
Early linear IgA bullous dermatosis Subepidermal blister formation.[27] Micrograph of linear IgA bullous dermatosis.jpg Linear IgA bullous dermatosis.jpg
Early febrile neutrophilic dermatosis (Sweet's syndrome) Neutrophilic and lymphohistiocytic infiltrate and edema.[28] Sweet's syndrome pathology.jpg Sweet's syndrome Crohn's disease.gif
Connective tissue disorders
  • Usually associated with epidermal changes.[1] (Systemic lupus erythematosis pictured)
Histopathology of systemic lupus erythematosus.jpg Butterfly rash of lupus erythematosus.jpg
Cutaneous small-vessel vasculitis
  • Neutrophils with nuclear dust (dashed arrows in image), with high affinity for postcapillary venules.[29]
  • Features of vascular injury: fibrinoid necrosis (asterisks) and erytrocyt extravasation (solid arrows)
Micrograph of cutaneous small-vessel vasculitis.jpg Cutaneous small-vessel vasculitis.jpg

Multinucleated giant cells

Suture granuloma, with multinucleated giant cells surrounding (grey) suture material.
  • Look for foreign bodies, conferring a diagnosis of foreign body granuloma.
  • Look for any specific appearance of the giant cells:

A Touton giant cell contains a ring of nuclei surrounding a central homogeneous cytoplasm, with foamy cytoplasm surrounding the nuclei.[30][31] The central cytoplasm (surrounded by the nuclei) may be both amphophilic and eosinophilic.[32]

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
  2. PAS is for evaluation of the epidermal basement membrane, blood vessels, and the presence of fungal organisms
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 A description of the findings attained so far is generally enough as a diagnosis in "not otherwise specified" cases, but may mention when it can be consistent with a diagnosis that is clinically suspected according to the referral.
  4. Parakeratotic mounds at the edge of follicular ostia.
  5. Pigmented purpuric dermatitis of Gougerot and Blum particularly have a tendency for lichenoid infiltrate.

References

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    - It also shows an example of circular coverage, with equal coverage distance in all four directions.
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