Skin nontumor


Common terms & patterns

Topic Completed: 1 June 2012

Minor changes: 29 September 2021

Copyright: 2002-2021,, Inc.

PubMed Search: cutaneous horn, pseudoepitheliomatous hyperplasia

Hillary Rose Elwood, M.D.
Christopher S. Hale, M.D.
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Cite this page: Elwood HR, Rosales C, Hale CS. Common terms & patterns. website. Accessed October 25th, 2021.
Definition / general
  • Acantholysis: loss of intercellular connections (desmosomes) between keratinocytes; occurs in pemphigus vulgaris and related disorders; causes change in cell shape from polygonal to round
  • Acanthosis: thickening of epidermis (squamous layer); rete ridges usually extend deeper into dermis
  • Atrophy: thinning of epidermis, associated with age or disease
  • Basophilic degeneration: age and sunlight related changes of collagen and elastic fibers
  • Blister: vesicle or bullae
  • Bullae: fluid filled area > 5 mm; either intraepidermal or subepidermal; intraepidermal bullae are due to spongiosis or acantholysis; subepidermal bullae are due to extensive papillary dermal edema
  • Calcinosis: deposit of calcium
  • Colloid bodies: also called Civatte bodies; apoptotic keratinocytes, are oval / round, immediately above or below epidermal basement membrane
  • Comedo: hair follicle infundibulum is dilated and plugged with keratin and lipids
  • Cyst: encapsulated cavity or sac lined by true epithelium
  • Dyskeratosis: abnormal, premature keratinization of keratinocytes below granular cell layer; often have brightly eosinophilic cytoplasm
  • Epidermolysis: alteration of granular layer with perinuclear clear spaces, swollen and irregular keratohyalin granules, increased thickness of granular layer; different from acantholysis
  • Epidermotropism: atypical lymphocytes present in epidermis (seen in cutaneous T cell lymphoma)
  • Erosion: discontinuity of skin causing partial loss of epidermis (compare to ulceration)
  • Excoriation: deep linear scratch, often self-induced
  • Exocytosis: normal appearing lymphocytes in epidermis (spongiotic dermatitis)
  • Horn: conical mass of cornifed cells
  • Hydropic (liquefactive) degeneration: basal cells become vacuolated, separated and disorganized
  • Hyperkeratosis: thickened cornified layer, often with prominent granular layer; keratin may be abnormal; either orthokeratotic (hyperkeratosis is exaggeration of normal pattern of keratinization with no nuclei in cornified layer) or parakeratotic (hyperkeratosis has retained nuclei in cornified layer)
  • Lentiginous: linear pattern of melanocytic proliferation within epidermal basal cell layer
  • Leukocytoclasis: karyorrhexis and destruction of neutrophils; occurs with neutrophilic vasculitis (also called leukocytoclastic vasculitis)
  • Lichenification: thick, rough skin with prominent skin markings usually due to repeated rubbing
  • Lichenoid interface change: destruction of basal keratinocytes, causing remodeling of basement membrane zone; also bandlike lymphocytic infiltrate
  • Macule: circumscribed flat colored area of any size
  • Nodule: solid, deeply extending lesion > 5 mm
  • Oncholysis: loss of integrity of nail substance
  • Papillomatosis: outward overgrowth of epidermis with elongation of dermal papillae
  • Papule: elevated and solid area, 5 mm or less
  • Parakeratosis: cells of cornified layer retain their nuclei, often less prominent or absent granular layer; normal for mucous membranes
  • Patch: flat discoloration > 5 mm
  • Papule: solid elevated lesion < 5 mm
  • Plaque: elevated flat topped area, usually > 5 mm
  • Poikiloderma: combination of atrophy, telangiectasia and pigmentary changes
  • Purpura: extravasation of red blood cells into the skin or mucous membranes
  • Pustule: intraepidermal or subepidermal vesicle or bullae filled with neutrophils
  • Scale: dry, horny, platelike excrescence usually due to imperfect cornification
  • Scale crust: parakeratotic debris, degenerating inflammatory cells and tissue exudate on surface of epidermis
  • Sinus: tract connecting cavities to each other or to the surface
  • Spongiosis: intraepidermal edema, causing splaying apart of keratinocytes in stratum spinosum (resembling a sponge), vesicles due to shearing of desmosomes
  • Ulceration: discontinuity of skin causing complete loss of epidermis and possible loss of dermis
  • Vesicle: fluid filed area, 5 mm or less
  • Wheal: itchy, transient, elevated area with variable blanching and erythema, due to dermal edema
See Abscess under Skin nontumor > Infectious Disorders
Cutaneous horn
Definition / general

Clinical features
  • Usually solitary
  • Predilection for the head and neck and hands of older persons
  • Hard yellow to brown skin excrescence composed of compact keratin resembling a horn
  • Can be straight or curved and can measure up to several centimeters in length

Case reports

Clinical images

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Cutaneous horn

Microscopic (histologic) description
  • Usually epidermal type keratin (with granular layer)
  • Occasionally has trichilemmal-like features (no granular layer but deep red granules) - termed trichilemmal horn
  • Examination of the base of the lesion is needed to determine the underlying etiology
  • Sometimes base contains epidermal hyperplasia without atypia

Microscopic (histologic) images

Contributed by Hillary Rose Elwood, M.D.

Low power

Verruca vulgaris

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Actinic keratosis with cutaneous horn

Exfoliative dermatitis / erythroderma
Clinical features
  • Total body erythema (> 90% of cutaneous surface) and scaling, due to drug reaction, allergic contact dermatitis, psoriasis, pityriasis rubra pilaris, malignancy
  • Associated with dermatopathic lymphadenitis
  • May clinically resemble chronic graft versus host disease (Ann Dermatol 2009;21:319)

Clinical images

Images hosted on other servers:

Various images

Microscopic (histologic) description
  • Nonspecific changes
  • May have lichenoid dermatitis

Differential diagnosis
Lichenoid dermatitis
  • A histological pattern, not a distinct clinical entity
  • Due to drug eruption, actinic keratosis, lupus erythematosus, acute graft versus host disease, regressing melanoma and dermatofibroma
  • May be a delayed hypersensitivity reaction
  • May present as a neoplasm
  • Micro description:
    • Dense, band-like lymphocytic infiltrate in dermis that obscures dermoepidermal junction
    • Cytoplasmic vacuolization of basal keratinocytes with a brightly eosinophilic cytoplasm; the nucleus becomes extruded to become round / oval eosinophilic bodies (colloid bodies)
    • Regenerated epithelium has a disorderly basement membrane
    • May have large cell acanthoma or solar lentigo within the lesion
Pseudoepitheliomatous hyperplasia
Definition / general
  • Pseudoepitheliomatous (pseudocarcinomatous) hyperplasia (PEH) is a histologic pattern, not a specific diagnosis
  • Histologic mimic of squamous cell carcinoma
  • PEH occurs in a wide range of settings such as:
    • Chronic irritation, including borders of ulcers and healing wounds, urostomy / colostomy sites, prior biopsy site, stasis ulcer, pyoderma gangrenosum, prurigo nodularis, lichen simplex chronicus, halogenoderma
    • Inflammatory dermatoses such as hypertrophic lichen planus, pemphigus vegetans, chronic arthropod bite
    • Infectious dermatoses such as tuberculosis verrucosa cutis, pyoderma vegetans, atypical mycobacterial infection, deep fungal infection
    • Overlying tumors such as granular cell tumor, cutaneous T cell lymphoma, CD30+ lymphoproliferative disorders, Spitz nevi, melanoma
  • Differential for PEH with intraepidermal neutrophilic microabscesses includes:

Case reports

Microscopic (histologic) description
  • Prominent acanthosis of epidermis and adnexal epithelium with deep, somewhat bulbous, downgrowths of epithelial cells that may appear invasive
  • Dermal fibrosis and reactive vascular proliferation may be present
  • In cases associated with an inflammatory or infectious process, there may be intraepidermal microabscesses
  • Often associated with trapping of elastic fibers within epidermis
  • Absent or minimal atypia, rare mitoses

Microscopic (histologic) images:

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Inflammatory infiltrate in dermis

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Surface epithelium

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Acanthotic squamous epithelium

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Mild chronic inflammation

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Pseudoepitheliomatous hyperplasia

Differential diagnosis
  • Pseudoepitheliomatous hyperplasia can be seen in a number of settings, as outlined above, and its presence should prompt a search for an underlying infectious process, inflammatory process or tumor as appropriate
  • Well differentiated squamous cell carcinoma:
    • Can be extremely difficult to impossible to distinguish PEH from squamous cell carcinoma (SCC), especially on superficial shave biopsies
    • PEH is mainly differentiated by clinical findings and / or the discovery of an underlying reason for its presence
    • Findings that favor SCC include increased mitoses particularly atypical mitoses, more pronounced cytologic atypia, perineural / lymphovascular invasion
Spongiotic dermatitis
  • Clinically correlates with eczematous dermatitis
  • Encompasses a large number of diseases, including allergic contact dermatitis and irritant contact dermatitis
  • Microscopic description: intraepidermal edema with clear spaces separating keratinocytes
    • Acute: also perivascular lymphocytic infiltrates in upper dermis, lymphocyte exocytosis
    • Subacute: focal parakeratosis, acanthosis, papillomatosis, eosinophils
    • Chronic: prominent parakeratosis, acanthosis, papillomatosis; may have minimal spongiosis; fibroplasia of papillary and upper reticular dermis; variable inflammatory infiltrate
    • May resemble early cutaneous T cell lymphoma, which has large numbers of cerebriform nuclei, Pautrier microabscesses, epidermotropism

Microscopic (histologic) images:

Contributed by Asmaa Gaber Abdou, M.D.

Spongiotic dermatitis

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