Home > E. Pathology by systems > Skin > actinic keratosis

actinic keratosis

Tuesday 6 July 2004

solar keratosis, senile keratosis, pre-epitheliomatous keratosis

WKP

Digital cases

- UI:906 - Actinic keratosis.
- UI:917 - Actinic keratosis.
- UI:1826- Actinic keratosis.
- JRC:10567 : Actinic keratosis.
- JRC:10569 : Actinic keratosis.

Definition: Actinic keratosis is a premalignant condition of thick, scaly, or crusty patches of skin

It is more common in fair-skinned people and it is associated with those who are frequently exposed to the sun, as it is usually accompanied by solar damage.

They are considered as potentially pre-cancerous, since some of them progress to squamous cell carcinoma, so treatment is recommended.

Untreated lesions have up to twenty percent risk of progression to squamous cell carcinoma.

Progressive development of these lesions occurs when skin is exposed to the sun constantly and thick, scaly, or crusty areas appear.

Clinical synopsis

The scaly or crusty portion is dry and rough. The lesions start out as flat scaly areas and later grow into a tough, wart-like area.

An actinic keratosis site commonly ranges between 2 and 6 millimeters in size, and may be dark or light, tan, pink, red, a combination of all these, or have the same pigment as the surrounding skin.

The lesion may appear on any sun-exposed area, such as the face, ears, neck, scalp, chest, backs of hands, forearms, or lips.

- May progress to frank malignancy.
- May remain stable.

Etiology

- Actinic keratosis is, as the name implies, associated with sun exposure.
- Long term exposure to the sun is the causative factor.
- Arsenic, hydrocarbons, and ionizing radiation may cause a similar lesion.

Pathogenesis

- Believed to represent a response of the skin to UV rays.

Epidemiology

It is seen primarily in the area of the face, upper back in light-skinned men and the legs of light-skinned women.

Actinic keratosis is very common, affecting half of the global population. It is seen more often in fair-skinned individuals, and prevalence may vary with geographical location and age.

People who take immunosuppressive drugs, such as organ transplant patients, are 250 times more likely to develop actinic keratoses that may lead to skin cancer.

Macroscopy

- The lesion may appear as a roughened area of skin with some evidence of hyperemia and a tendency to ulceration.

- The lesion is usually less than 1.0 cms in diameter.

Microscopy

Histologically, the actinic keratosis lesion may be visualized as a dysplasia or carcinoma in situ of the skin.

Actinic keratosis usually shows focal parakeratosis with associated loss of the granular layer of, and thickening of the epidermis.

The normal ordered maturation of the keratinocytes is disordered to varying degrees, there may be widening of the intracellular spaces, and they may also have some cytologic atypia, such as abnormally large nuclei.

The underlying dermis often shows severe actinic elastosis and a mild chronic inflammatory infiltrate

Instead of the normal orderly progression of basal layer, stratum spinosum, granular cell layer, stratum corneum, there is a loss of polarity of cells.

Mitoses are seen at layers above the basal layer.

There is a failure of orderly maturation of the nucleus from vesicular to condensed to fragmentaton and loss of nuclear materials

There is a tendency to abrupt and unscheduled keratinization

There is a tendency to hyperchromatic and aberrant nuclear morphology.

In addition, some evidence of infiltration of the upper dermis with inflammatory cells is often noticed.

Actinic keratosis is almost always accompanied by a bluish discoloration (solar elastosis) of the papillary dermis indicative of UV damage to the connective tissue of the papillary dermis.

Diagnostic biopsy is undertaken in only a small percentage of actinic keratoses diagnosed clinically. The clinical accuracy in the recognition of actinic keratoses varies from 74 to 94%.

- epdiermal changes

  • The usual actinic keratosis is characterized by focal parakeratosis, with loss of the underlying granular layer and a slightly thickened epidermis with some irregular downward buds.
  • Uncommonly, the epidermis is thinner than normal.
  • variable loss of the normal orderly stratified arrangement of the epidermis
  • cytological atypia of keratinocytes, which varies from slight to extreme.
  • Sometimes the dysplastic epithelium shows suprabasal cleft formation.
  • There is often a sharp slanting border between the normal epidermis of the acrotrichia and acrosyringia and the parakeratotic atypical epithelium of the keratosis.
  • However, dysplastic epithelium may involve the infundibular portion of the hair follicle.
  • The parakeratotic scale may sometimes pile up to form a cutaneous horn.
  • Large keratohyaline granules are sometimes present in actinic keratoses.

- dermal changes

  • The dermal changes include actinic elastosis, which is usually quite severe, and a variable, but usually mild, chronic inflammatory cell infiltrate.
  • The grade of solar elastosis is a marker of epithelial UV damage.

Variants

Variants or subtypes of actinic keratosis that have been described include pigmented, hypertrophic, atrophic, lichenoid, proliferative, acantholytic, and Bowenoid.

- bowenoid actinic keratosis

  • The term ‘bowenoid keratosis’ may be used when the atypia is close to full thickness.
  • This variant differs markedly from the ‘de novo’ form of Bowen’s disease.

- inflammatory actinic keratosis (lichenoid actinic keratosis)

  • Inflammatory keratoses may develop during chemotherapy of malignant disease with fluorouracil and its analogues.
  • There is vascular telangiectasia and a moderately heavy mixed inflammatory cell infiltrate in the upper dermis.
  • An inflammatory response is also present in actinic keratoses before they progress to squamous cell carcinomas, unrelated to any therapies.
  • The inflammation subsides rapidly following this conversion.

- hyperkeratotic actinic keratosis

- hypertrophic actinic keratosis

  • The dorsal hand is a common place for hypertrophic actinic keratosis.
  • Such lesions often show changes of lichen simplex chronicus due to chronic irritation and rubbing of the lesion

- pigmented actinic keratosis

  • Pigmented actinic keratosis may show heavy melanin pigmentation of the basal layer keratinocytes.
  • Clinically and histologically these may mimic a melanocytic proliferation.

- atrophic actinic keratosis

Sorafenib

Inflammation of actinic keratoses has also been reported following therapy with sorafenib, a multitargeted tyrosine-kinase inhibitor.

Some actinic keratoses progress to squamous cell carcinoma with this therapy.

Immunosuppression

In all types of actinic keratoses in immunosuppressed patients there is usually marked atypia of the keratinocytes; multinucleate forms may be present. Confluent parakeratosis and verruciform changes may also occur.

Differential diagnosis

- squamous cell carcinoma in situ, clonal variant
- bowenoid papulosis

- epidermal dysmaturation after chemotherapy or transplantation

  • Actinic keratoses must be distinguished from the epidermal dysmaturation that may be seen following chemotherapy or transplantation.
  • It is a histological diagnosis characterized by disruption of keratinocyte maturation, loss of polarity, widened intercellular spaces, irregular large nuclei, mid-epidermal mitotic figures, and apoptosis
  • Colchicine intoxication can also result in dysmaturation with metaphase-arrested keratinocytes and basal vacuolar change.
  • Actinic keratoses must be distinguished from the epidermal dysmaturation that may be seen following chemotherapy or transplantation.
  • It is a histological diagnosis characterized by disruption of keratinocyte maturation, loss of polarity, widened intercellular spaces, irregular large nuclei, mid-epidermal mitotic figures, and apoptosis.
  • Colchicine intoxication can also result in dysmaturation with metaphase-arrested keratinocytes and basal vacuolar change.

See also

- cutaneous epidermal tumors
- actinic cheilitis
- cutaneous horn
- squamous cell carcinoma in situ

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