Skin nontumor


Common terms & patterns

Editorial Board Member: Jonathan D. Ho, M.B.B.S., D.Sc.
Carina Dehner, M.D., Ph.D.
Louis P. Dehner, M.D.

Last author update: 30 January 2023
Last staff update: 30 January 2023

Copyright: 2002-2023,, Inc.

PubMed Search: Spongiotic dermatitis, psoriasiform dermatitis

Carina Dehner, M.D., Ph.D.
Louis P. Dehner, M.D.
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Cite this page: Dehner C, Dehner LP. Common terms & patterns. website. Accessed September 21st, 2023.
Definition / general
  • This topic represents an overview of common terms and microscopic findings of the most frequently seen reaction pattern in dermatopathology
  • Acantholysis:
    • Separation of cell - cell connections (desmosomes) between keratinocytes leading to single, rounded keratinocytes
    • Seen in pemphigus variants and related disorders
  • Acanthosis:
    • Thickening of epidermis
    • Elongated rete ridges usually extend into dermis
    • Can be regular (all rete pegs at roughly the same level) or irregular (rete pegs at different levels of the papillary dermis)
  • Anagen:
    • Hair during growth phase
  • Anaplasia:
    • Atypical nuclei (abnormal in size and shape) and pleomorphism (variation in nuclear characteristics)
  • Asteroid body:
    • Collections of eosinophilic material in sporotrichosis or star shaped inclusion in sarcoidal giant cells / other granulomatous processes
  • Atrophy:
    • Epidermal:
      • Decreased thickness due to reduced numbers of keratinocytes
      • Epidermis may appear flat at its base with loss of rete ridge pattern
      • May occur after inflammation / certain topical treatments
    • Dermal:
      • Thinning of dermal layer due to loss of collagen / elastin
      • May occur after steroids and atrophodermas
  • Banana bodies:
    • Yellow-green, banana shaped fibers in the dermis; can be due to exogenous or endogenous causes
  • Basal vacuolar degeneration:
    • Also known as liquefactive / hydropic degeneration
    • Small vacuoles resembling bubbles in the basal layer
    • Often associated with individually necrotic keratinocytes
    • May or may not have an associated band of infiltrate obscuring the dermoepidermal junction
    • Associated with vacuolar / lichenoid interface dermatitis (e.g., cutaneous lupus, erythema multiforme, lichen planus)
  • Basement membrane:
    • Thin membranous layer of extracellular matrix which is separating the epidermis from the dermis
  • Birefringence:
    • Optical capacity of a material with a refractive index that depends on polarization and propagation of direction of light
  • Blister:
    • Fluid filled skin lesions
    • May result from separation of keratinocytes (intraepidermal blisters) or loss of adhesion between the epidermis and the underlying dermis (subepidermal blisters)
    • Examples of diseases commonly associated with blisters include autoimmune bullous dermatoses, interface dermatitis, spongiotic dermatitis and some viral and bacterial infections
  • Bullae:
    • Fluid filled lesion > 1 cm (= large blister)
  • Calcinosis:
    • Cutaneous deposition of insoluble calcium in response to damage, metabolic derangements or undetermined etiology
  • Catagen:
    • Hair during regressive phase
  • Caterpillar bodies:
    • Eosinophilic bodies present within the roof of the blister formed in porphyric bullous eruptions, such as porphyria cutanea tarda
  • Civatte / colloid bodies:
    • Globular residue of apoptotic keratinocytes
    • Typically pink in color
    • Referred to as Civatte bodies when present within the epidermis and as colloid bodies when in the papillary dermis
    • Classically described in lichen planus but may be seen in all causes of interface / lichenoid dermatitis
  • Comedo:
    • Dilated follicular infundibulum filled with keratin, lipid (not visible with standard stains) and often basophilic debris
    • Bacterial colonies may be present
    • Classical lesion in acne vulgaris
  • Cornoid lamellae:
    • Layers of parakeratosis often in a ~45° angle overlying an area of diminished granular layer with dyskeratotic cells present at the base
    • Classically seen in porokeratosis variants
  • Cowdry bodies:
    • Cowdry A: intranuclear inclusion in herpes simplex virus
    • Cowdry B: intranuclear inclusion in cytomegalovirus, adenovirus, poliovirus
  • Crust:
    • Hyperkeratosis (often parakeratosis) with inspissated serum with or without Inflammatory cells (= wet scale)
  • Cyst:
    • Encapsulated cavity or sac lined by true epithelium
  • DEJ:
    • Dermoepidermal junction
  • Dermal papilla (hair):
    • Layer that is located at the base of the hair follicle
  • Desmosome:
    • Adhesion molecule between two cells
  • Diffuse infiltrate:
    • sheets of inflammatory ells diffusely infiltrating dermis
  • Donovan body:
    • Rod shaped, oval organisms within histiocytes in granuloma inguinale
    • Characteristic bipolar staining pattern gives safety pin appearance
    • Highlighted by Warthin-Starry and Giemsa stains
  • Dutcher body:
    • Spherical, intracytoplasmic immunoglobulin inclusions that appear intranuclear due to folding into the nucleus of plasma cells
    • Seen in plasmacytoma
  • Dyskeratosis:
    • Abnormal, premature keratinization of keratinocytes below granular cell layer
    • Often have brightly eosinophilic cytoplasm with or without a pyknotic nucleus
  • Effacement:
    • Synonymous with consumption of the epidermis
    • Refers to thinning of the epidermis / loss of rete ridges
    • Commonly seen in melanoma
  • Elastolysis:
    • Defect in elastic fibers leading to atrophy, skin laxity
  • Elastorrhexis:
    • Fragmentation of elastic fibers; systematic elastorrhexis seen in pseudoxanthoma elasticum
  • Elastosis:
    • Degenerative changes in elastic fibers (increase in abnormal elastin) leading to loss of elastic quality of the dermis
  • Epidermolysis:
    • Alteration of granular layer with perinuclear clear spaces, swollen and irregular keratohyalin granules, increased thickness of granular layer
    • Different from acantholysis
    • Classically seen in epidermolytic ichthyosis and keratodermas but may be seen in epidermal nevi, isolated keratoses and incidentally
  • Epidermotropism:
    • Atypical individual cells present in epidermis without significant spongiosis
    • Most commonly refers to atypical lymphocytes in cutaneous T cell lymphomas but can be seen in other malignant neoplasms, including melanoma and metastatic deposits
  • Erosion:
    • Discontinuity of skin causing partial loss of epidermis
  • Excoriation:
    • Deep scratch with abrupt loss of epidermis without full thickness loss at an ulcer
    • Excoriation may result in partial or full thickness epidermal loss (erosion versus ulcer)
    • Often self induced
  • Exocytosis:
    • Inflammatory cells migrating into the epidermis (commonly seen in spongiotic dermatitis)
    • Lymphocytes, neutrophils and eosinophils most commonly seen
  • Festooning:
    • Undulating pattern of the dermal papillae
    • Commonly seen underneath bullae / blisters (e.g. in porphyria cutanea tarda / subepidermal autoimmune bullous diseases)
  • Fibrinoid necrosis:
    • Necrosis associated with vascular damage
  • Fibrosis:
    • Increased amount of fibroblasts forming a scar or skin thickening
  • Flame figure:
    • Deposition of eosinophil granules from degranulated eosinophils and nuclear debris on dermal collagen fibers with or without surrounding histiocytes
    • Classically seen in Wells syndrome (eosinophilic cellulitis) but may be seen in a variety of eosinophil rich diseases
  • Foam cell:
    • Histiocyte whose cytoplasm is replaced by variably sized lipid vacuoles
    • Commonly seen in xanthoma variants, lipidized dermatofibromas and some histiocytoses
  • Follicular plugging:
    • Process of abundant hyperkeratotic material plugging up follicular ostia
  • Globi:
    • Amphophilic collection of mycobacteria, classically seen in leprosy
  • Granuloma:
    • Collection of macrophages forming a cluster / round structure in response to certain types of inflammation (foreign material, microorganisms, etc.)
  • Grenz zone:
    • Thin layer of uninvolved dermis directly beneath the epidermis, separating it from an inflammatory cell infiltrate or tumor
    • Grenz zones classically seen in granuloma faciale, leukemia cutis, dermatofibromas, lepromatous leprosy and solar elastosis
  • Hemidesmosome:
    • Adhesion molecule between cell and basal lamina
  • Henderson-Patterson body:
    • Cytoplasmic viral inclusion bodies often filling cup shaped cavity space in molluscum contagiosum (molluscum bodies)
  • Horn (cutaneous horn):
    • Massive vertically oriented hyperkeratosis (parakeratotic, orthokeratotic or mixed) most commonly overlying a keratinocytic neoplasm
    • Importance lies with the lesion which underlies the horn which may be malignant in a significant minority
  • Horn cyst:
    • Hyperkeratotic epithelial structure presumably due to abrupt complete keratinization
  • Hypergranulosis:
    • Thickening of the stratum corneum
  • Hyperkeratosis:
    • Thickened cornified layer (stratum corneum)
    • Keratin may be abnormal
    • Either orthokeratotic (typically compact keratin with no nuclei) or parakeratotic (nuclei in cornified layer)
  • Inferior follicle:
    • Inferior segment of the follicle from the bulge to the base of the follicle
  • Infundibulum:
    • Upper segment of the hair follicle
  • Interface dermatitis:
    • Pattern of inflammatory dermatitis characterized by basal layer vacuolation with or without a band of inflammation obscuring the dermoepidermal junction
    • When band-like lymphocytic infitlrate present, referred to as lichenoid interface or lichenoid dermatitis
  • Isthmus:
    • Segment between the sebaceous gland duct opening and the hair bulge
  • Kamino bodies:
    • Eosinophilic bodies associated with spitz nevi
  • Koilocyte:
    • Keratinocyte that underwent structural changes due to viral infection
  • Lentiginous:
    • Linear pattern of melanocytic proliferation within epidermal basal cell layer
  • Leukocytoclasis:
    • Vascular karyorrhexis of degenerating neutrophils is a feature of neutrophilic vasculitis (also called leukocytoclastic vasculitis)
  • Leukocytoclastic vasculitis:
    • Inflammatory reaction of blood vessels including fibrinoid changes within the vessel walls
  • Lichenification:
    • Thick, rough skin with prominent skin markings usually due to repeated rubbing
    • Associated with hyperkeratosis
  • Lichenoid dermatitis:
    • Inflammatory pattern characterized by basal vacuolar change and a band of inflammatory cells at the dermo - epidermal junction
  • Lichenoid infiltrate:
    • Band-like lymphocytic infiltrate at the dermoepidermal junction
  • Macule:
    • Flat lesion less than 1.0 cm
  • Medlar body:
    • Also known as sclerotic bodies
    • Brown, round fungal cell in between yeast and hyphal state with the appearance of copper pennies
    • Diagnostic for chromoblastomycosis
  • Michaelis-Gutmann body:
    • Round, calcified structures located within the cytoplasm of histiocytes in malakoplakia
    • Stain with Perls stain for iron and von Kossa for calcium
  • Mikulicz cells:
    • Large foamy histiocytes containing rods of klebsiella rhinosclermomatis in rhinoscleroma
  • Munro microabscess:
    • Neutrophilic collections in the stratum corneum
    • Classically seen in psoriasis
  • Necrobiosis:
    • Altered / necrotic collagen
    • Seen in granuloma annulare and other necrobiotic lesions
  • Nevus:
    • Often used to refer to a benign tumor of melanocytes but may also refer to a hamartomatous lesion of any component of the skin (epidermis, dermis, blood vessels etc.)
  • Nodular inflammation:
    • Inflammatory cells forming nodular collections
  • Nodule:
    • Solid lesion (> 1 cm) whose vertical dimension is greater than its horizontal
  • Oncholysis:
    • Separation of the nail plate from the underlying nail bed
    • Associated with psoriasis, trauma, onychomycosis, thyrotoxicosis and phototoxic drug ingestion
  • Owl eye inclusion:
    • Term used to describe a cells infected by cytomegalovirus
  • Pagetoid spread:
    • Single malignant cells involving the epidermis
  • Panniculitis:
    • Lobular:
      • Inflammation of fat involving predominantly the fat lobules (e.g., erythema induratum, pancreatic panniculitis, etc.)
    • Septal:
      • Inflammation of fat involving predominantly the septae in between the fat lobules (e.g., erythema nodosum)
  • Papillary dermal edema:
    • Extracellular accumulation of fluid leading to thinning of the dermis
  • Papillary mesenchymal body:
    • Structures associated with follicular differentiation; can serve as helpful clue in follicular type adnexal neoplasms, such as trichoepithelioma / trichoblastoma
  • Papillomatosis:
    • Finger-like undulation of the epidermis with upward expansion of dermal papillae
    • May have associated epidermal hyperplasia
  • Papule:
    • Raised lesion < 1 cm
  • Parakeratosis:
    • Retention of nuclei in the stratum corneum
    • Normal for mucous membranes without stratum granulosum
  • Parasitized macrophages:
    • Macrophages infected by parasites present within their cytoplasm (e.g., in leishmaniasis)
  • Patch:
    • Flat lesion > 1 cm
  • Pautrier microabscess:
    • Collections of atypial lymphocytes involving the epidermis; seen in mycosis fungoides
  • Periadnexal inflammation:
    • inflammatory cells predominantly surrounding the adnexal structures
  • Perivascular inflammation:
    • Inflammatory cells predominantly surrounding vasculature
  • Plaque:
    • Raised, relatively flat topped lesion > 1 cm
  • Poikiloderma:
    • Combination of atrophy, telangiectasia and pigmentary changes
  • Pseudoepitheliomatous hyperplasia:
    • Exaggerated acanthosis of the epidermis mimicking squamous cell carcinoma
    • Commonly seen in the epidermis overlying prior procedure sites, chronic inflammation, granular cell tumor, blastomycosis
  • Psoriasiform epidermal hyperplasia:
    • Acanthosis of the epidermis with regular elongation the rete ridges
  • Purpura:
    • Extravasation of red blood cells into the skin or mucous membranes with or without inflammation
  • Pustule:
    • Intraepidermal or subepidermal vesicle or bullae filled with neutrophils
  • Scale:
    • Dry, horny, plate-like excrescence corresponding to hyperkeratosis
    • Usually due to imperfect cornification
  • Schaumann body:
    • Laminated calcified structure
    • Seen in sarcoidosis but rare in skin lesions
  • Sclerosis:
    • Excess connective tissue with decreased amount of fibroblasts
  • Shadow cells:
    • Cells without a nucleus due to prior cell death
  • Sinus:
    • Tract connecting cavities to each other or to the surface
  • Spongiform pustule of Kogoj:
    • Collection of neutrophils within the stratum spinosum
    • Associated with spongiosis at the periphery (e.g. seen in psoriasis)
    • Seen in psoriasis, including pustular variants
  • Spongiosis:
    • Intraepidermal edema causing splaying apart of keratinocytes in stratum spinosum (resembling a sponge)
    • Intercellular adhesion proteins (desmosomes) often visible
    • Vesicles due to shearing of desmosomes
  • Squamous eddies:
    • Whorled profiles composed of keratinocytes (e.g. seen in inverted follicular keratoses)
  • Storiform:
    • Growth pattern consisting of spindle cells arranged in a cartwheel-like pattern
    • Classically seen in dermatofibrosarcoma protuberans (DFSP)
  • Telogen:
    • Hair during resting phase
  • Ulceration:
    • Discontinuity of skin causing complete loss of epidermis and possible loss of dermis with accompanying surface fibrin deposition or exudate with or without granulation tissue response
  • Verocay body:
    • Structure composed of 2 nuclear palisades with central eosinophilic cytoplasmic processes
    • Classically seen in schwannoma
  • Vesicle:
    • Fluid filled lesion < 1 cm
  • Von Hansemann cells:
    • Large macrophages containing Michaelis-Gutmann bodies seen in malakoplakia
  • Wheal:
    • Itchy, transient, elevated area with variable blanching and erythema
    • Due to dermal edema
Granulomatous dermatitis
  • Similar pattern seen in various clinical settings
    • Sarcoidosis
    • Necrobiosis lipoidica (associated with diabetes mellitus)
    • Granuloma annulare (localized, generalized, etc.)
    • Palisaded neutrophilic and granulomatous dermatitis
    • Granulomatous reaction to foreign material

Contributed by Carina Dehner, M.D., Ph.D.
Perivascular and interstitial inflammation

Perivascular and interstitial inflammation

  • Bacterial
    • Impetigo:
      • Nonbullous or bullous forms
      • Gram positive cocci are the trigger
    • Staphylococcus scalded skin syndrome:
      • Sterile subcorneal split of epidermis
      • Driven by toxins from certain Staphylococcus aureus strains
    • Rhinoscleroma:
      • Diffuse inflammatory infiltrate underlying submucosa, Mikulicz cells present
      • Trigger: Klebsiella pneumoniae
    • Erythrasma:
      • Erythematous intertriginous patches
      • Triggered by Corynebacterium minutissimum infection
  • Viral
    • Herpes virus:
      • Multinucleated keratinocytes with chromatin margination and molding
      • Mucosal sites (HSV1 / 2) or dermatome distribution (varicella zoster virus)
    • Epstein-Barr virus (EBV):
      • Infectious mononucleosis, oral hairy leukoplakia, Gianotti-Crosti syndrome
      • EBV virus can be detected by in situ hybridization
    • Cytomegalovirus:
      • Large, intranuclear inclusions with halo
    • Molluscum contagiosum:
      • Molluscum bodies
      • Trigger: poxvirus
  • Spirochetes
    • Syphilis:
      • Psoriasiform hyperplasia, mixed pattern dermatitis
      • Treponema pallidum
  • Fungal
    • Dermatophytosis:
      • Neutrophils in stratum corneum sandwich sign: parakeratosis or compact orthokeratosis underlying basket weave type stratum corneum
    • Majocchi granuloma:
      • T. rubrum
      • Fungi surrounding degenerate hair shafts
    • Pityriasis (tinea) versicolor:
      • Malassezia
      • Need to see spores and hyphae in stratum corneum
    • Blastomycosis:
      • May induce pseudoepitheliomatous hyperplasia
  • Arthropods / parasites
    • Demodex:
      • Commonly seen, mostly incidental
      • If exuberant, can induce pathologic changes leading to dry eye, chalazion, etc.
    • Scabies:
      • Potassium hydroxide preparation (KOH prep) can be done on bed site
      • Itchy for years

Contributed by Carina Dehner, M.D., Ph.D.
Eggshells of scabies

Eggshells of scabies

Mixed pattern dermatitis

Mixed pattern dermatitis

Lichenoid dermatitis
  • Lichenoid dermatitis, with or without interface
    • Band-like inflammation and basal vacuolar degeneration (lichen planus, etc.)
  • Interface changes without lichenoid inflammation (discoid lupus, erythema multiforme)
    • Basal vacuolar degeneration and dyskeratotic keratinocytes only (erythema multiforme)
    • Basal vacuolar degeneration and dyskeratotic keratinocytes at the dermoepidermal junction + superficial and deep perivascular, periadnexal inflammation and increased dermal mucin (discoid lupus erythematosus)

Contributed by Carina Dehner, M.D., Ph.D.
Lichenoid interface dermatitis

Lichenoid interface dermatitis

  • Septal panniculitis
    • Erythema nodosum
  • Lobular panniculitis: diverse group associated with rheumatoid arthritis, gout (Arch Dermatol 1998;134:501)
    • Pancreatic panniculitis: lobular fat necrosis with saponification and ghost cells
    • Erythema induratum: prominent fat necrosis, histiocytes, giant cells, granulomas, vasculitis
    • Lupus panniculitis: may show lymphoid follicles
    • Sclerosing panniculitis (lipodermatosclerosis)

Contributed by Carina Dehner, M.D., Ph.D.
Saponification and ghost cells

Saponification and ghost cells

Perivascular dermatitis
  • Wide spectrum of diagnoses
    • Superficial: dermal hypersensitivity with or without eosinophils, urticaria
    • Superficial and deep: arthropod bite, connective tissue diseases
Psoriasiform dermatitis
  • Psoriasiform hyperplasia (e.g. psoriasis, lichen simplex chronicus, pityriasis rubra pilaris, etc.)

Contributed by Carina Dehner, M.D., Ph.D.
Psoriasiform hyperplasia

Psoriasiform hyperplasia

Alternating parakeratosis and orthokeratosis

Alternating parakeratosis and orthokeratosis

Sclerosing dermatitis
  • Localized scleroderma (morphea)
  • Guttate morphea
  • Systemic sclerosis

Contributed by Carina Dehner, M.D., Ph.D.
Sclerosis of dermal collagen

Sclerosis of dermal collagen

Spongiotic dermatitis
  • Spongiosis: accumulation of fluid leading to intercellular edema in the epidermis
  • Acute: wet scale + extreme spongiosis (= intraepidermal vesicles) + eosinophils in the inflammatory infiltrate
  • Subacute: hyperkeratosis with little parakeratosis + mild acanthosis + mild spongiosis
  • Chronic: mild hyperkeratosis + marked acanthosis + minor spongiosis

Contributed by Carina Dehner, M.D., Ph.D.


Vasculopathic / vasculitic dermatitis
  • Leukocytoclastic vasculitis: associated with infections, drugs, autoimmune diseases, etc.
    • Granuloma faciale: form of leukocytoclastic vasculitis, Grenz zone
    • Erythema elevatum diutinum
  • Occlusive vasculopathy: fibrin thrombi filling venules and capillaries

Contributed by Carina Dehner, M.D., Ph.D.
Fibrinoid material within vessels

Fibrinoid material within vessels

Vesiculobullous dermatitis
  • Subcorneal split:
    • Pemphigus foliaceus:
      • Intercellular IgG, C3 on direct immunofluorescence (DIF)
      • Sparing of basal layer
    • Acute generalized exanthematous pustulosis (AGEP):
      • Neutrophils, eosinophils in dermal infiltrate
      • Negative DIF
  • Suprabasal split:
    • Pemphigus vegetans:
      • Neutrophilic abscesses
      • Intercellular IgG, C3 on DIF
    • Pemphigus vulgaris:
      • Eosinophils, neutrophils, tombstone appearance
      • Intercellular IgG, C3 on DIF
    • Darier disease:
      • Acantholysis and dyskeratosis
      • Negative DIF
  • Intraepidermal split:
    • Bullous arthropod bite:
      • Spongiotic edema, eosinophils
      • Negative DIF
  • Subepidermal split:
    • Dermatitis herpetiformis:
      • Neutrophils in the dermal papillae
      • Granular IgA on DIF
    • Porphyria cutanea tarda:
      • Cell poor split
      • IgG around superficial dermal vessels on DIF
    • Bullous pemphigoid:
      • Eosinophil rich
      • Linear IgG and C3 at the dermoepidermal junction on DIF
    • Linear IgA bullous dermatosis:
      • Neutrophil rich
      • Linear IgA at the dermoepidermal junction on DIF

Contributed by Carina Dehner, M.D., Ph.D.
Subcorneal acantholysis

Subcorneal acantholysis

Acantholytic blister with tombstone

Acantholytic blister with tombstone

Board review style question #1

What is a Majocchi granuloma?

  1. Deeper fungal infection in which fungi surround degenerate hair shafts
  2. Necrotizing granuloma seen in infectious diseases, such as tuberculosis
  3. Nonnecrotizing granuloma seen in diseases such as sarcoidosis
  4. Palisaded histiocytic granulomatous process with central fibrin, seen in rheumatoid nodule
  5. Palisaded histiocytic granulomatous process with central mucin, seen in granuloma annulare
Board review style answer #1
A. Majocchi granuloma is a deep fungal infection involving hair follicles caused by dermatophytes, such as T. rubrum

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