Melanoma in situ (syn. melanotic precancerosis) is a preliminary stage of malignant melanoma. It is a multiplication of atypical melanocytes (cells responsible for the dark color) in the epidermis.
The atypical cells have not yet broken through the basal membrane, i.e. the membrane between the epidermis and subcutis. Untreated, a malignant melanoma (malignant black skin cancer) can develop from the melanoma in situ. There are several types of malignant melanoma. Melanoma in situ is not a specific type of tumor, but merely a description of the localization and spread of the atypical cells.
Epidemiology
Typically, melanoma in situ occurs after the age of 50. As a rule, men are affected twice as often as women. Further risks are:
- Light skin type
- Blonde or red hair and
- Many years of strong light exposure
Causes of melanoma in situ
The exact cause for the development of melanoma in situ is not known. However, it is suspected that the development has similar causes as the development of other skin tumors. Above all, long-term UV exposure (tanning) is regarded as the cause.
For this reason, areas that are regularly exposed to UV radiation are particularly affected by melanoma in situ. This includes the head, neck, forearms and lower legs. However, all parts of the body can be affected.
The DNA of the melanocytes is damaged by the UV radiation. If the body’s repair mechanisms are no longer sufficient, a malignant new cell can develop. This cell grows outside the normal regulatory mechanisms and continues to multiply unchecked.
Diagnostics
The diagnosis of melanoma in situ is usually made by the dermatologist. With the help of strong magnifying aids and a lot of experience, the dermatologist can distinguish a melanoma in situ from a harmless mole. To be on the safe side, a histological examination (tissue examination) of the melanoma should always be performed.
This is the only way to determine the exact stage in which the tumor is located. Over the years, the few cells develop into grey-brown to black pigmented foci, which initially look like a normal mole. These foci grow uninhibited, unevenly and without a sharp edge, which distinguishes them from harmless liver spots.
Further symptoms do not usually occur, which makes it difficult to recognize a melanoma in situ. Usually, a suspicious mole is completely removed. The entire melanoma is always surgically removed in situ with a lateral safety margin and the small wound is then sutured again.
If there are many melanomas in situ, or if they are in unfavorable locations, it is also possible to laser the melanoma in situ. Another possibility is the removal by means of X-ray irradiation with a maximum radiation dose of 100 Gray. However, if the melanoma in situ is already advanced and thus degenerates, irradiation is no longer permitted.
