Dermatology Made Easy is based on the most popular topics from DermNet NZ's vast array of material. The book combines the essential focus of the ‘Made Easy’ book series with the authority and knowledge base of DermNet NZ's unparalleled resources.
Author: Vanessa Ngan, Staff Writer, 2005.
Skin, or cutaneous, metastasis (plural ‘metastases’) refers to growth of cancer cells in the skin originating from an internal cancer. In most cases, cutaneous metastasis develops after the initial diagnosis of the primary internal malignancy (e.g. breast cancer, lung cancer) and late in the course of the disease. In very rare cases, skin metastasis may occur at the same time or before the primary cancer has been discovered and may be the prompt for further thorough investigation.
Skin metastasis may also occur from a skin cancer, usually melanoma. The original or ‘primary’ melanoma produces metastases or ‘secondary’ growths in surrounding or distant skin sites and other tissues such as the lungs or brain.
Skin metastasis occurs when cancerous cells break away from the primary tumour and make their way to the skin through the blood circulation or lymphatic system. Most malignant tumours can produce skin metastasis, but some are more likely to do so than others. When the following cancers have metastasised, they have quite a high chance of affecting the skin.
The incidence of skin metastasis varies but is somewhere between 3-10% in patients with a primary malignant tumour.
The sex and age of an individual also appears to determine the frequency of skin metastasis in certain primary cancers. The reason for this is unknown.
|Organ of cancer origin||% Skin metastasis in women||% Skin metastasis in men|
Below lists the common internal cancers that cause skin metastasis in decreasing order of frequency according to sex and age group.
|<40 yr.||>40 yr.||<40 yr.||>40 yr.|
SCC in the oral cavity
Most skin metastasis occurs in a body region near the primary tumour. The first sign of skin metastasis is often the development of a firm, round or oval, mobile, non-painful nodule. The nodules are rubbery, firm or hard in texture and vary in size from barely noticeable lesions to large tumours. These may be skin coloured, red, or in the case of melanoma, blue or black. Sometimes multiple nodules appear rapidly. The skin metastases may break down and ulcerate through the skin. Specific patterns include:
Depending on the location of the primary tumour, skin metastasis display certain characteristic features.
|Organ of cancer origin||Features of skin metastasis|
|Colon and stomach||
The underlying primary tumour needs to be treated. However, in most cases where skin metastasis has occurred, the primary cancer is widespread and may be untreatable. In this case, palliative care is given and includes keeping lesions clean and dry. Debridement can be done if lesions bleed or crust. Other therapies that may be helpful include:
In many cases, skin metastasis causes disfigurement and discomfort. Removal of skin lesions by simple excision may enhance the patient’s quality of life but has little effect on the final outcome that is dictated by the primary cancer.
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