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Skin cancer

Introduction to skin cancer

In this section, you can find information on:

  • The skin and skin cancer
  • The treatment options available
  • Specific information on brachytherapy and the procedure
  • The healthcare professionals involved in delivering brachytherapy
  • Potential benefits of brachytherapy
  • Potential side-effects to consider
  • Frequently asked questions
  • Useful questions to ask your doctor

About the skin

The main purpose of the skin is to form a barrier between the body and the environment. It protects the body against the loss of fluids and nutrients, and against damage and infection by external forces and materials 1. In additional skin produces vitamin D when exposed to sunlight and the skin has an important function in the regulation of the body temperature 2.

The skin is made up of two layers of tissue; the ‘epidermis’ layer is nearest to the surface of the skin and the ‘dermis’ is the layer underneath 3.

The epidermis is only about one-tenth (0.1) of a millimeter thick 4. The epidermis consists mainly of cells which are in very close contact with each other. This way an effective barrier against dehydration, poisoning and infection is formed. The main cell types of the epidermis are 5:

  • Basal cells – cuboidal cells at the base of the epidermis that can proliferate and that form a continuous source of new cells which are pushed upwards to the surface where they are eventually shed
  • Squamous cells – flat cells that are pushed up from the basal cell layer. These cells are located closer to the surface, in normal situations they do not proliferate. Eventually these cells will produce keratin, lose their nucleus, die and are lost via shedding 
  • Melanocytes – cells that are also located at the base of the epidermis and that produce a pigment called melanin, which gives skin its color.

The dermis is a little bit thicker than the epidermis, between 1 and 4 mm, and consists of many different cell types and structures that are embedded in a matrix of proteins and fibers 6. The dermis contains nerves, blood vessels, sweat glands, sebaceous glands, hair follicles, connective tissue etc. 7

What is skin cancer?

Skin cancer occurs when during life time skin cells accumulate damage to their DNA and start to grow in an uncontrolled way.  Exposure to ultraviolet sunlight is the principal pathogenic factor for development of skin cancer 8. As a consequence most skin cancers develop in areas of the body that are often exposed to sunlight such as the head and face 9.

Skin cancer mainly originates in the epidermis and can be categorized into 2 major groups: melanoma and non-melanoma skin cancers (NMSC). The latter group consists primarily of basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) 10.

Non melanoma skin cancers (NMSC):


Basal cell carcinoma (BCC)


Approximately 75% of all skin cancers. These lesions originate in the basal cell layer of the epidermis.


Malignant melanoma


This type of lesion originates in the melanocytes and is far less common than basal cell or squamous cell skin cancer (4% of all skin cancers), but is responsible for the majority of skin cancer deaths.

Squamous cell carcinoma (SCC)


Approximately 20% of all skin cancers. These lesions originate in the squamous cell layer of the epidermis. With SCC often also actinic keratosis (AK) is present.




(~1% of all skin cancers). These include for example Merkel Cell Carcinoma.



Since Melanoma is usually not treated with brachytherapy as primary treatment, further sections of this website will focus on nonmelanoma skin cancer and it’s treatment. For more information on radiation therapy for melanoma we recommend to see for example the website of the American Cancer Society:

Picture: Basal cell carcinoma of the nose

Risk factors for developing skin cancer

The following risk factors are known to increase the risk of developing skin cancer:

  • Sun exposure – the ultraviolet rays from the sun can damage the skin.  Increased exposure to the sun  increases the risk of developing skin cancer later in life 8
  • Skin color – people with fair skin are at increased risk of developing skin cancer. Melanin, the pigment in the skin protects the skin from damage by UV. Less melanin increases the risk of sun burn and developing skin cancer later in life 11

Other risk factors include for example contact of the skin with carcinogenic chemicals, use of immune suppressive medication and genetic predisposition 12, 13

What tests are used to confirm a diagnosis?

As most skin cancers occur on sun-exposed- and thus visible areas of the body, they are usually noticed at a very early stage. They appear as a small lump on the skin and can be smooth and waxy, or scaly and crusty and may bleed spontaneously 14. Non melanoma skin cancer is often present for several months at moment of diagnosis, but because of the slow growth and the location in visible areas the lesions are usually smaller than 2 cm in diameter at diagnosis .

If you notice any unusual looking growths on the skin it is important to talk to a healthcare professional.

Usually a healthcare professional with expertise in the diagnosis of skin cancer will be able to recognize a skin cancer by looking at it, sometimes with help of a handheld magnifying device called a dermascope. A biopsy of the growth can give more information on the type of cancer and the depth of the lesion. This involves a small sample of tissue being taken for examination under a microscope. 

How do I know how advanced the cancer is?

The stage of a cancer is a description of how widespread it is. For skin cancers staging includes a description of the tumor’s size and location, whether it has grown into nearby tissues or bones, whether it has spread to the lymph nodes or any other organs, and certain other factors.

Because basal cell skin cancer is almost always cured before it spreads to other organs, it is seldom staged unless the cancer is very large. Squamous cell cancers have a greater (although still small) risk of spreading, so staging may sometimes be done, particularly in people who have a high risk of spread.

Table: staging of non melanoma skin cancer (excluding SCC of the eyelid)




Primary tumor cannot be assessed


No evidence of primary tumor


Carcinoma in situ


Tumor 2 cm or less in greatest dimension with fewer than two high-risk features x


Tumor >2 cm in greatest dimension or
Tumor any size with two or more high-risk features x


Tumor with invasion of maxilla, mandible, orbit, or temporal bone


Tumor with invasion of skeleton (axial or appendicular) or perineural invasion of skull base

X High-risk features for the primary tumor (T) staging: depth/invasion: > 2mm thickness, Clark level ≥IV, or perineural invasion; anatomic location: primary site ear, or primary site non-hair-bearing lip; differentiation: poorly differentiated or undifferentiated 15


1. Madison, K. C. (2003, July 23). Barrier Function of the Skin: "La Raison d'Être" of the Epidermis. Journal of Investigative Dermatology, 121, 231-241.
2. Mostafa, W. Z., & Hegazy, R. A. (2014, February 8). Vitamin D and the skin: Focus on a complex relationship: A review. Journal of Advanced Research
3. Wysocki, A. B. (1999, December). Skin anatomy, physiology, and pathphysiology. Nursing Clinics of North America, 34(4), 777-797.
4. Sandby-Møller, J., Poulsen, T., & Wulf, H. C. (2003). Epidermal Thickness at Different Body Sites: Relationship to Age, Gender, Pigmentation, Blood Content, Skin Type and Smoking Habits. Acta Derm Venereol, 83, 410-413
5. Baroni, A., Buommino, E., De Gregorio, V., Ruocco, E., Ruocco, V., & Wolf, R. (2012). Structure and function of the epidermis related to barrier properties. Clinics in Dermatology, 30, 257-262
6. Odland, G. (1991). Structure of the skin. In L. A. Goldsmith (Ed.), Physiology, biochemistry, and molecular biology of the skin. Oxford: Oxford University Press.
7. Grath, J. A., & Uitto, J. (2010). Anatomy and Organization of Human Skin. In T. Burns, S. Breathnach, N. Cox, & C. Griffiths (Eds.), Rook's Textbook of Dermatology
8. Narayanan, D. L., Saladi, R. N., & Fox, J. L. (2010, September). Ultraviolet radiation and skin cancer. International Journal of Dermatology, 49(9), 978-986
9. Davis, R. E., & Spencer, J. M. (1997). BAsal and squamous cell cancer of the facial skin. Curr Opin Otolaryngol Head Neck Surg, 5, 86-92.
10. Madan, V., Lear, J. T., & Szeimies, R.-M. (2010). Non-melanoma skin cancer. Lancet, 375, 673-685
11. CDC. (2014). Skin Cancer; what are the risk factors? Retrieved April 8, 2014, from Centers for disease control and infection:
12. Leiter, U., & Garbe, C. (2008). Epidemiology of melanoma and nonmelanoma skin cancer-the role of sunlight. Adv Exp Med Biol, 624, 89-103
13. Surdu, S., Fitzgerald, E. F., Bloom, M. S., Boscoe, F. P., Carpenter, D. O., Haase, R. F., et al. (2013, November). Occupational exposure to arsenic and risk of nonmelanoma skin cancer in a multinational European study. Int J Cancer, 133(9), 2182-2191
14. Albert, M. R., & Weinstock, M. A. (2003). Keratinocyte Carcinoma. CA: A Cancer Journal for Clinicians, 53(5), 292-302
15. Edge, S., Byrd, D. R., Compton, C. C., Fritz, A. G., Greene, F. L., & Trotti, A. (Eds.). (2010). AJCC Cancer Staging Manual (7th ed., Vol. XV). Springer.