Degrees of actinic keratosis

Actinic keratosis can be divided into different degrees and types. The Olsen classification classifies actinic keratosis according to its clinical appearance. This means that the appearance as well as the nature of the skin changes are used as classification criteria.

There are three degrees according to Olsen which are explained in detail in separate sections (see below). A further classification is the differentiation of histological subtypes. This classification differentiates actinic keratoses with regard to their fine tissue characteristics.

For this classification, a skin sample must be examined under the microscope. There are 6 histological subtypes. Actinic keratoses are classified as grade 1 according to Olsen in the stage in which they become visible at the earliest time.

These are mild actinic keratoses. Their appearance is slightly reddish and spotty. In most cases they are more palpable than nodular structures.

One can see single or few incoherent skin lesions, which are blurred. With a size of only a few millimetres they are often overlooked. In the case of a moderately severe actinic keratosis one speaks of a grade 2 according to Olsen.

The appearance of this stage is clearer and easier to recognize than with a grade 1 according to Olsen. Whitish or reddish discoloration of the skin is visible, which can lead to scaling. This is caused by excessive keratinization (hyperkeratosis).

The skin feels rough and knotty hardenings are possibly palpable. Brownish discoloration of the skin areas is also possible. Usually several areas of the so-called “sun terrace” are affected.

These include the forehead, the bridge of the nose, the scalp and the décolleté. A grade 3 according to Olsen is found in severe actinic keratosis. These are advanced skin changes that require action.

Thick, wart-like skin changes are visible and palpable. A brown and white discoloration is also typical. The skin lesions are firmly attached to the surface and cannot be scaled or scraped off. The transition to white skin cancer is fluid at this stage. Bleeding of the skin lesions is possible on contact.

Early stage/budding stage of actinic keratosis

The development of actinic keratosis is a gradual process and is basically not noticed by those affected. A recurring exposure to UV radiation, be it through extensive sunbathing or visits to the solarium, working outdoors or frequent sunburns in childhood, leads to permanent damage in the skin cells and ultimately to precancerous lesions or early forms of cancer. This process takes place over several years, so that visible changes are usually not present until old age.

In this sense, very early forms cannot be seen at all – the cell changes take place virtually in the non-visible area. The first visible changes, which could be described as early or initial stages, are usually red, blotchy skin symptoms. These can be very inconspicuous and can be initially overlooked, especially in the case of somewhat darker skin types.

In most cases, the changes in the early stages of actinic keratosis are better felt than seen as a kind of small nodules. However, affected persons often do not notice this so much. Especially changes on the scalp, a frequent localization of actinic keratosis, are thus neglected.