ARTICLE
Auteur(s) : W Sterry, S Chimenti, R MacKie
Definition
Skin cancer has become the most frequent cancer in humans. Within
the complex structure of the skin each of the numerous cell types
can undergo malignant degeneration, explaining the multitude of
different skin cancer entities. However, the vast majority of skin
cancers are made up of three tumours: malignant melanoma, basal
cell carcinoma and squamous cell carcinoma. The two latter skin
cancer types are often referred to as nonmelanoma skin cancer. The
main causative agent for skin cancer is UV irradiation.
Along with the rising incidence of skin cancer, dermatologists
have been challenged to provide effective measures for prevention,
early diagnosis as well as treatment adapted to the stage of skin
cancer. In this respect, European dermatology finds itself among
the international leaders, and has contributed landmark
publications.
Nonmelanoma Skin Cancer
Basal cell carcinoma (BCC) presents with reddish papules and
plaques, sometimes with aggressively growing tumours, located
predominantly on the face, but also on the trunk. It is a malignant
epithelial tumour deriving from the epidermis. The main risk
factors for BCC development include fair skin pigmentation, UV
exposure, chemical exposure to arsenic salts, and chromosomal
abnormalities. Rarely, it occurs within certain families. The
incidence of BCC in Europe is about 150 new cases per 100,000
inhabitants per year, but has already reached 1000 in Australia.
Squamous cell carcinoma (SCC) and its intraepithelial precursor,
actinic keratosis, represent a second malignancy of epidermal
keratinocytes. Lesions begin as small and rough elevations in
sun-exposed areas, and may develop into ulcerated and invasive
tumours with metastatic potential. The primary etiology is UV
radiation. Risk factors include age over 40, fair skin type,
occupation with UV exposure and chronic immunosuppressive therapy.
While the incidence of SCC compares to BCC, actinic keratosis
affects up to 25% of the adult Caucasian population living in the
Northern Hemisphere.
Melanoma
Malignant melanoma arises from melanocytes, pigment cells living
within and protecting the skin. Due to increasing UV exposure, the
incidence of melanoma has doubled every eight years since the
seventies. At present, in Europe one person out of eighty will
develop malignant melanoma during his lifetime, but the white
population in Australia already has a lifetime risk for melanoma of
one person out of twenty!
Melanoma of the skin presents as an irregular, asymmetric
macule, plaque or nodule with variable pigmentation. Once it has
reached deeper parts of the skin by invasion from the upper layers,
access to lymph vessels or even blood vessels opens, and lymphatic
or hematogenous spread will occur. Patients with generalised
metastatic disease have an overall 5 year survival below 5%.
Most frequently, cutaneous melanoma occurs on the face, the
lower legs in females and the back of males. However, any anatomic
site may be involved, including the mucous membranes.
Other common skin cancers
Many cell types resident within the skin may undergo malignant
degeneration. Frequently seen cutaneous neoplasias include
cutaneous lymphoma, Merkel cell carcinoma, and Kaposi sarcoma.
Their diagnosis and treatment requires special dermatological
expertise.
Skin tumor registries
Registries have been established for several skin tumours in
various European countries, including registries for melanoma (the
melanoma registry of the German Dermatological Society is the
largest world wide), epithelial skin cancers and cutaneous
lymphoma.
Requirements for diagnosis
Diagnosis, especially in early phases with high chances for
healing, requires expert knowledge provided by dermatologists. The
following diagnostic tools and therapeutic options should be
available, some of which require specialised skin tumour centres:
- – Facilities for examination of skin and mucous
membranes.
- – Epiluminescence microscopy.
- – Diagnostic skin biopsy, dermatohistological
examination of excised tumours and their lateral and basal margins
and processing of sentinel lymph node biopsies.
- – Availability of nuclear medicine services to provide
radioactive labeling for sentinel lymph node biopsies.
- – Special dermatopathological techniques such as
cytology, immunohistology and in selected cases molecular
biology.
- – Lymph node and subcutaneous tissue sonography.
- – X-ray, computer tomography (CT) and magnet resonance
imaging (MRT) investigations (for melanoma staging
investigations).
- – Bone scintigraphy (for metastatic melanoma).
- – Positron emission tomography (PET) investigation (for
metastatic melanoma).
- – PCR investigations for tyrosinase or gp100 oncoprotein
or determination of MIA protein in the peripheral blood may be
valuable.
Therapy
In many European countries, the National Cancer Societies have
asked dermatological oncologists to develop guidelines for medical
care of the most important skin cancers such as melanoma,
epithelial skin cancer, cutaneous lymphomas, Merkel cell carcinoma
or Kaposi sarcoma. One source for such guideline is the German
Working Group for Dermatological oncology (ADO;
http://www.dkfz-heidelberg.de/ado/index.htm). However, optimal care
often requires interdisciplinary co-operation, particularly with
general surgeons, neurosurgeons, radiotherapists, and medical
oncologists. On the European level, development of guidelines has
become an important activity of the EDF. The Euroguideline for
basal cell carcinoma was finished in 2004, and others are in
progress.
The professional treatment of skin cancer involves both surgical
and oncological measures, both of which are part of dermatology.
Since research on skin cells is without doubt performed with
dermatological leadership, also malignant tumours derived from skin
cells are best understood and treated by dermatologists, also and
particularly if these cells have metastasised throughout the
body.
Oncological treatment requires special medical training. While
most monochemotherapies as well as low dose cytokine treatments are
part of the regular training program of every dermatologist,
polychemotherapy or high dose cytokine treatment requires special
knowledge and skills which can be taught in specialised centres;
such centres should have expertise in these therapies, and may be
certified. Treatment protocols that include stem cell transfer and
bone marrow ablations should be performed by medical
oncologists.
Dermatooncological care requires a special infrastructure, which
should include all diagnostic facilities mentioned above plus
surgical facilities for excision of primary tumors, sentinel lymph
nodes or skin metastases, as well as plastic reconstruction In
addition, inpatient services should be capable of a administering
chemotherapy, polychemotherapy, and chemoimmunotherapy.
Preventive measures
Prevention includes the clinical investigation of the entire skin
organ by dermatologists in collaboration with specially trained
physicians, who should refer patients with doubtful skin lesions.
After treatment for skin cancer, patients require follow up
investigations in dermatology facilities. 2% of patients with a
melanoma will develop a second primary melanoma, and most patients
with epithelial skin cancer will develop further lesions.
Primary prevention is probably the most important single factor
in prevention of melanoma. Education of the public regarding a
rational approach to UV light exposure must be achieved by public
campaigns as well as in the individual patient dermatologist
interactions.
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