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Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Glossary of dermatopathological terms

This glossary describes dermatopathological terms. It is arranged alphabetically within four sections.

  1. Some general pathological terms
  2. Pathological terms used for the epidermis
  3. Pathological terms used for the dermis
  4. Pathological terms used for the subcutis

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A. General

  • The process by which a cell undergoes a process of dying/self destruction in the presence of a suitable signal(s) from the cell's command centre, the nucleus.
  • The process by which the body lays down collagen as part of the healing process.
  • It may be a consequence of the normal healing response leading to a scar, or it may be abnormal, as in scleroderma and keloid scar formation.
  • The multi-step process by which the body attempts to remove or contain foreign material/organisms from the body or repair any injury sustained by tissues.
  • The process includes recognition of foreign material, vascular dilatation and leakage of fluid and cells into the tissues, attraction of immune cells to the site of injury, removal of the foreign organisms/dead material by the immune cells and release of chemical signals to initiate the repair process.
  • The inflammatory process may be acute or chronic, reflecting the time frame over which this occurs/takes place.
  • Abnormal proliferation of cell(s).
  • The cells of a neoplasm are usually derived from the same cell line (a clonal proliferation).
  • Neoplasms may be benign (i.e. have no potential to spread to distant sites via the blood or lymphatic system) or malignant (i.e. they have the potential to spread (or metastasise) into the blood or lymphatic systems to seed, invade and proliferate at distant sites in other remote organs or tissues).
  • Swelling of the tissue due to leakage of fluid from vessels into surrounding tissues due to an inflammatory process or due to elevated pressure within vessels which forces fluid out of the vessels.
  • With skin conditions like eczema, there may be oedema between keratinocytes leading to the histological appearance called spongiosis – a reflection of the underlying inflammatory process that causes eczema.
  • The histological appearance of the changes of the nuclear material of the nucleus as it undergoes apoptosis.
  • It is characterised by darkening and condensation (shrinking and compacting) of the nucleus.
  • An abnormal proliferation of cells that can be thought of as synonymous with neoplasm.
  • Also used as a descriptive term for a swelling or a lump of uncertain origin.

B. Epidermis

  • The keratinocytes are seen ‘floating apart’ from each other because of loss of desmosome cell connections
  • Different conditions have unique patterns of acantholysis, for example, in pemphigus vulgaris, the acantholysis is just above the basal layer of the epidermis (suprabasilar acantholysis or suprabasilar clefting) but the basal layer remains intact (tombstone appearance). In contrast, in pemphigus foliaceus, the acantholysis is higher up, just below the stratum corneum.
Darier disease pathology
  • Thickening of the epidermis and elongation of the rete ridges due to thickening of the spinous layer.
  • May be associated with enlargement of rete pegs.
Atrophy of the epidermis
  • Thinning of the epidermis.
  • A larger fluid-filled blister within the epidermis (intraepidermal blister) or below it (subepidermal blister). See also vesicle, below.
Cornoid lamella
  • Parakeratotic column overlying focal hypogranulosis and dyskeratotic keratinocytes. Characteristic of porokeratosis.
  • Parakeratotic keratinocytes, serum and inflammatory cells within the stratum corneum.
  • Abnormal keratinocytes with hypereosinophilic cytoplasm (pinker on H&E).
  • Shrunken hyperchromatic nucleus, i.e., small and dark-staining.
  • Characteristic of cutaneous T cell lymphoma (mycosis fungoides).
  • Localisation of abnormal T lymphocytes within the epidermis.
  • Aggregates of these abnormal T cells form Pautrier's microabcesses.
  • Random passage of inflammatory cells into the epidermis.
  • May consist of lymphocytes, neutrophils or eosinophils.
Follicular plugging
  • Accumulation of keratin at the shoulder region of the hair follicle in response to an inflammatory reaction.
  • Most commonly seen in the lichenoid reaction pattern, especially lichen planopilaris, pityriasis rubra pilaris and cutaneous lupus erythematosus.
Horn cyst
  • Intra-epidermal keratin-filled space resembling a cyst.
  • An apparent increase in the granules of keratinocytes of the granular layer.
  • Thickening of the epidermis with thickening of the stratum corneum.
  • Epidermal differentiation of keratinocytes is normal.
  • Compacted cells with loss of normal basket weave pattern (compact hyperkeratosis, compact orthohyperkeratosis).
  • The process by which epidermal cells called keratinocytes undergo maturation and differentiation as the cell migrates from the basal layer to the stratum corneum.
  • Cells appear pale with vacuolated cytoplasm.
  • Small dark and condensed (pyknotic) nucleus.
  • Keratohyaline granules may be seen in the cytoplasm.
  • Due to wart virus infection.
  • ‘Basket weave’ appearance of the stratum corneum, as in normal skin.
  • There are no nuclei within the stratum corneum cells.
Pagetoid spread
  • Proliferation of cells within the epidermis in a random pattern of distribution giving a ‘buckshot’ scatter pattern.
  • In malignant melanoma, describes random appearance of melanoma cells in the epidermis.
  • Typical of extramammary Paget's disease and some Bowen disease (intraepithelial squamous cell carcinoma).
  • Undulating appearance of the epidermis.
  • Nuclei are retained within the stratum corneum.
  • Parakeratosis indicates that the epidermis is inflamed or injured.
  • Differing patterns may or may not help diagnosis.
  • The epidermis is invaginated, or pushed inside itself, to form a cavity that resembles a cyst.
Pseudoepitheliomatous hyperplasia
  • Pronounced thickening due to proliferation of all layers of the epidermis.
  • Elongation of the rete pegs is irregular.
  • Similar in appearance to squamous cell carcinoma but due to non-malignant skin growth.
Psoriasiform hyperplasia
  • Inflammatory pattern seen in psoriasis and other conditions.
  • Rete pegs are longer than usual due to cellular proliferation (the production of increased numbers of cells).
  • This elongation is regular.
  • Suprapapillary plate is thinned in chronic plaque type psoriasis.
  • Collection of neutrophils in the epidermis.
  • Pustules do not always indicate infection.
  • Munro microabscesses are tiny pustules in the stratum corneum and spongiform pustules of Kogoj are in the spinous layer. These are characteristic of acute or early psoriasis.
  • Subcorneal pustules are seen in several skin disorders.
  • Spaces between keratinocytes are more apparent than normal.
  • The spaces are filled with leaked tissue fluid (oedema).
  • Indicates that the epidermis is inflamed.
  • Most commonly seen in eczema but can be seen incidentally or as part of other skin conditions.
  • If severe, visible blisters may occur because the keratinocytes are not sticking together firmly.
  • Eosinophilic spongiosis is the term used when eosinophils predominate in the inflammation, for example in atopic eczema, pemphigus and pemphigoid.
Squamous eddy
  • Abnormal round or whorled area of keratinisation that occurs in the epidermis instead of normal keratinisation.
  • Marker of disordered proliferation, maturation and differentiation of keratinocytes.
  • Usually seen within squamous cell carcinomas.
Transepidermal elimination
  • Process in which there is apparent rejection or elimination of collagen or elastin material from the dermis through the epidermis.
  • Can occur with other materials/substances as well.
Vacuolar degeneration
  • Patchy damage to the basal layer of the epidermis seen with lichenoid reactions.
  • Cells have membrane-bound cavities that look like holes; they contain a watery secretion.
  • The basal cells may swell when injured i.e., they undergo vacuolar change.
  • If the injury is severe, the cell undergoes apoptosis and becomes a Civatte body (colloid body). These shrunken dead cells have an eosinophilic cytoplasm and small dark nucleus.
  • Small fluid-filled blister(s) within or below the epidermis.
Viral inclusions
  • Small particles within keratinocyte cytoplasm. Various patterns are seen.
  • Viral causes include warts and herpes infections.

C. Dermis

Atrophy of the dermis
  • Thinning of the dermal layer due to loss of collagen.
  • Process by which calcium is deposited in the skin.
Dermal oedema
  • Process by which fluid leaks out from blood and lymphatic channels into the surrounding dermis.
  • Collagen bundles appear to spread out.
  • Process of increasing the amount of elastic tissue and improving the pliability of the skin, contributing to dexterity of the fingers for example.
  • Solar elastosis refers to a degenerative basophilic change in sun exposed dermis.
Flame figures
  • Pink (eosinophilic) degenerate collagen bundles and eosinophil granules.
  • Characteristic of Wells syndrome, insect bites and any condition in which there are a lot of eosinophils.
Foam cells
  • Lipid (or fat)-laden histiocytes.
  • Various patterns of chronic inflammation in which there is a mixture of cells including histiocytes.
  • May include multinucleated giant cells.
  • May include necrosis, foreign material or microorganisms, depending on the cause.
  • Granulomas form in response to foreign bodies, certain infections (tuberculosis, leprosy) and inflammatory skin diseases (granuloma annulare, granuloma faciale, sarcoidosis).
Grenz zone
  • Area of uninvolved zone of superficial dermis.
  • Separates the epidermis from an inflammatory or tumour cell infiltrate of the dermis.
Haemosiderin deposition
  • The process by which the haemoglobin derived from blood is broken down in the skin leaving dark brown or rusty-orange marks.
  • Smooth, ‘ground glass’ appearance due to damaged collagen fibres.
Interface dermatitis
  • Generally refers to a mild lichenoid-like reaction in the interface between epidermis and dermis.
  • Inflammation does not obscure the basement membrane.
Lichenoid reaction
  • Inflammatory pattern centred on the basal layer of the epidermis and upper dermis in a dense ‘band-like’ distribution.
  • Cellular infiltrate is predominantly lymphocytes.
  • Basement membrane may no longer be visible.
Mucin / myxomatous change
  • Deposition of extra ground substance.
  • Exaggerated normal healing response that occurs as a reaction to certain underlying skin diseases.
  • Bluish (basophilic), indistinct or blurry appearance of collagen bundles.
  • Due to accumulation of mucopolysaccharides.
  • Characteristic of granuloma annulare and necrobiosis lipoidica.
Nodular or diffuse dermatitis
  • A nonspecific term which refers to whether a specific finding occurs in discrete (nodular) areas in the skin or in a nonlocalised (diffuse) pattern.
Papillary mesenchymal bodies
  • Focal increase in number of fibroblasts in stroma beneath epithelial papillary body formation in trichoepithelioma.
Peri-adnexal inflammation
  • Inflammation around adnexal structures, like hair follicles or sweat glands.
Perivascular dermatitis
  • Inflammation centred around the small vessels in the skin, without evidence of vasculitis.
Perivascular lymphocytic infiltrate
  • Lymphocytes clustered around blood vessels.
Pigment incontinence
  • Melanin deposits in upper dermis due to inflammation affecting the melanocytes within the basal layer.
  • Frequently seen with lichenoid reaction.
  • Damage and death of endothelial lining cells of blood vessels due to infiltration by inflammatory cells (neutrophils or lymphocytes).
  • Leucocytoclastic vasculitis refers to endothelial damage by neutrophils, with disintegration of neutrophil nuclei into fragments (leucocytoclasia or nuclear dust).
  • Lymphocytic vasculitis is not characterised by leucocytoclasia.
  • Vasculitis may also be associated with granulomatous inflammation.

D. Subcutis

  • Inflammation of the fat.
  • Different histological patterns depend on the cause.
  • Lobular panniculitis affects the fat cells themselves.
  • Septal panniculitis affects the supporting fibrovascular areas in between the fat lobules.
  • Mixed septal and lobular panniculitis describes a mixture of the two patterns.
  • May be associated with vasculitis.

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Author: Dr Anthony Yung, dermatologist, Waikato District Health Board.

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