BASAL CELL CARCINOMA

This is normally abbreviated to BCC and is actually the most common cancer that humans develop. Thankfully it is rarely fatal and if detected early and dealt with properly, is usually curable.

WHAT CAUSES BASAL CELL CARCINOMAS TO DEVELOP?

Excessive exposure to UV radiation (sun burns) is the main cause of Basal Cell Carcinomas. People with fair skin and blue eyes have less ability to tan and thus less resistance to UV radiation and are therefore more prone to developing Basal Cell Carcinomas. Intermittent severe burns (tourists) rather than daily exposure to UV (farmer) results in a higher risk of getting Basal Cell Carcinomas. There are several rare genetic conditions which also predispose people to Basal Cell Carcinomas but these are so uncommon that they will not be discussed here.

HOW DO BASAL CELL CARCINOMAS DEVELOP?

Ultraviolet light from the sun penetrates into the skin and energises oxygen molecules within the cells of the epidermis. These energised oxygen molecules (oxygen free radicals) have the ability to damage the DNA in cells. If enough damage is done to sensitive parts of the DNA of skin cells this may trigger one (or several) of those cells to turn cancerous. The cells at the bottom layer of the epidermis are known as the basal cell layer. If one of these cells turns cancerous and a tumour results, it is known as a basal cell carcinoma.

DO BASAL CELL CARCINOMAS SPREAD?

Once a basal cell carcinoma has formed, the cells within it continue to multiply. Fortunately basal cell carcinomas do not have the ability to metastasize (spread) via the bloodstream or the lymphatics and as a result cannot spread to organs within the body or to one's lymph glands. Instead, basal cell carcinomas invade locally. They grow into the skin where they have arisen and slowly destroy the tissues beneath them and around their edges. This often results in the formation of a sore that bleeds easily and has the appearance of having been gnawed away by a rat. This giving rise to the colloquial term of "rodent ulcer". Of interest is that basal cell carcinomas rarely produce any pain even when a sore has developed.

IF BASAL CELL CARCINOMAS DON'T SPREAD, ARE THEY A PROBLEM?

Basal Cell Carcinomas become problematic when they start destroying sensitive tissues such as one's eyelids, nose or where they invade deeply and start growing into underlying muscle and bone. Some Basal Cell Carcinomas have the ability to invade nerve fibres and then spread along these fibres. If neglected for years, Basal Cell Carcinomas may ultimately follow nerve fibres all the way into the spinal cord or brain. This is fortunately very rare.

ARE THERE DIFFERENT TYPES OF BASAL CELL CARCINOMAS?

There are several types of BCC which are named according to their appearance.

  1. Nodular / Micronodular / Nodulocystic
  2. Ulcerated
  3. Superficial
  4. Morphoeic
  5. Multicentric  

All of the types have much the same growth patterns except for morphoeic BCC. Morphoeic BCC looks like a flat scar in the skin and this gives it it's name. The term "morphoea" means scar in Greek. It has a deceptive appearance and thus tends to be diagnosed at a later stage. It also has the ability to track under the surface of the skin and is therefore often much larger than one thinks. This has implications when planning treatments.

HOW ARE BASAL CELL CARCINOMAS DIAGNOSED?

Most Basal Cell Carcinomas have very specific appearances and can be easily diagnosed just by looking at them. Where there is uncertainty, the use of a skin microscope (dermatoscope) usually aids diagnosis. If there is still uncertainty then it becomes necessary to do a biopsy. A small piece of the lesion is removed after numbing the area with local anaesthetic, and sent to the pathology laboratory for testing.

HOW DOES ONE TREAT BASAL CELL CARCINOMAS?

Surgery

The most definitive form of treatment, which has the highest cure rate, is to do a surgical excision. A safety margin of normal looking skin needs to be included around the BCC just to make sure that one is completely clear of any microscopic extensions (roots) that have spread a bit further. In cosmetically and functionally sensitive areas, such as the nose or eyelids, or when treating recurrent; morphoeic or very large Basal Cell Carcinomas, it is prudent to use a technique called frozen section to increase one's ability to ensure complete removal of the BCC.

How is a frozen section done?

To do a frozen section it is necessary for the pathologist to come into theatre. The BCC is removed by the surgeon and carefully labelled so that the pathologist knows which way it is orientated. (the numbers of a clock face are used.) The pathologist takes the specimen to a lab within the theatre complex, where the sample is then frozen (using dry ice) within a special resin. This makes it possible for the pathologist to cut the specimen into very thin (3 microns thick) slices that can then be stained and looked at under a microscope.The pathologist checks the underside and all the edges of the specimen to make sure that there is no sign of any BCC. If BCC is found on an edge, the pathologist then informs the surgeon of exactly which edge and the surgeon then removes more tissue from this area. This is then further tested by the pathologist. Another name for this is Moh's micro-graphic surgery, named after Dr Moh who first developed his technique in 1938.

OTHER TREATMENTS

Aldara cream

If a BCC is very superficial and does not appear clinically to have invaded into the skin, then it is possible to try treating it with Aldara cream. The active ingredient is Imiquimod, which stimulates one's immune system to attack the BCC. Various treatment regimes can be followed but generally use for 5 weeks is required. During treatment, the BCC becomes inflamed and a scab develops. This falls off 2-3 weeks after treatment ceases.

Curettage

Smaller Basal Cell Carcinomas can be treated by curettage. This is usually performed by dermatologists who use a sharp curette to scrape the BCC off the skin's surface. This leaves a raw area which is cauterised forming a scab.

PDT
Liquid Nitrogen
Efudix cream