What is BCC?
BCC is a malignant tumour of the pluripotential epithelial cells of the deepest layers of the epidermis and hair follicles (stratum basale). Ironically the tumour does not arise from the basal cells of the epidermis.
How common is it?
BCC is the most common tumour of humans, accounting for more than 50% of all the tumours removed (More than 1,3 million per annum in the USA alone). Despite this incidence, these tumours account for <0.1% of all cancer deaths in humans. BCC is at least 3-4 times more common than SCC. BCC occurs on sun-exposed areas of light-skinned patients. BCC has been described in darkly pigmented patients, but is exceptionally rare. This is a disease of advancing age and is more common in the 50+ age group. Men are affected slightly more than women.
What causes BCC?
The causes of both BCC and SCC can be logically divided into environmental factors and host (patient) factors. Interestingly, BCC has not been generated experimentally by UV radiation alone, suggesting an interplay between factors.
- Ultraviolet (UVA & UVB) which comes from Sunlight.
Most of the UVB and all UVC are filtered by the ozone layer. UVA which is not filtered was initially thought to be non-cancer causing, but is now thought to be a potent cause with UVB. Recently, high dose UVA (as found in tanning beds) has been shown to be cancer causing. The amount of UV reaching the surface is dependent on factors such as weather conditions, season, time of day, latitude and ozone depletion. Interestingly, infra-red (heat) has been shown to be a co-factor in accelerating the cancer causing effect of UV.
As early as 1775, the cancer causing effect of hydrocarbons was identified. These chemical may be found in wood preservative, fuel oils, die mold lubricant and roofing industries. The pollutant, dimethyl benzanthracene is found where incomplete combustion of organic fuel occurs, both in the atmosphere and in tobacco smoke (where the concentration is much higher !).
- Skin Colour
The effects of DNA damage are modified by the amount of melanin, which absorbs UV radiation. Skin colour is genetically determined. Fitzpatrick has classified skin colour into 6 types based on the colour and the reaction to the first summer exposure – it is important to note that he did not distinguish any specific racial groups. The higher the Fitzpatrick type, the less likely the individuals’ risk of skin cancer.
|TYPE||COLOUR||REACTION TO FIRST EXPOSURE|
|I||White||Always burns, never tans|
|II||White||Usually burns, tans with difficulty|
|III||White||Sometimes burns, average tan|
|IV||Light Brown||Rarely burns, tans with ease|
|V||Dark Brown||Very rarely burns, tans very easily|
|VI||Black||Never burns, always tans|
- Other Rare Causes
Few genetic syndromes are associated with BCCs are : Gorlin’s Syndrome, Basex Syndrome, Rombo Syndrome, Unilateral basal cell nevus Syndrome and Nevus Sebaceous of Jadassohn. Lowered immune function may also cause BCC and conditions such as HIV, organ transplant immune-suppression, other cancer and chemotherapy may predispose to BCC.
There are many different ways in which BCC may present (see below). Generally, BCC has a tendency to be locally destructive.
Although there are suggestive features, the diagnosis can only be secure after a biopsy. Here are some histology photos – the dark purple cells represent cancer.
The overall cure rate for BCC is directly related to the stage of the disease and the type of treatment used. The traditional methods of treatment involve the use of cryosurgery (freezing), radiation therapy, electrodesiccation (heating), and surgical excision. Each of these methods is useful in specific clinical situations. Depending on case selection, these methods have cure rates ranging from 85% to 95%.
This traditional treatment usually relies on surgical margins ranging from 4 mm to 10 mm, depending on the diameter of the. Recurrence rate for tumours larger than 3cm is increased. BCC of the lips, ears, eyes, scalp, and nose are characteristically more aggressive, and surgery is usually suggested.
Electrodesiccation and curettage.
Although it is a quick method for destroying the tumor, adequacy of treatment cannot be assessed. Tumors >3 cm have a very high recurrence rate and should not be treated by this method. I personally don’t employ this method as the scarring is particularly unattractive.
Cryosurgery may be considered for patients with small, clinically well-defined primary tumors. It is especially useful for debilitated patients with medical conditions that preclude other types of surgery. Some swelling and blistering is usual following treatment, followed by an scab which usually resolves in 1-4 weeks. Permanent pigment loss at the treatment site is unavoidable and it should thus only be used for Caucasians.
Radiation therapy is a logical treatment choice, particularly for patients with primary lesions requiring difficult or extensive surgery (e.g., eyelids, nose, or ears). Cosmetic results are generally good to excellent Radiation therapy can also be used for lesions that recur after a surgery. It must be remembered that this is a financially costly option, and may preclude or complicate future surgery.
Carbon dioxide laser.
This method is best applied to the superficial type of basal cell carcinoma. It may be considered when a patient has a clotting problem. A more useful option may be to resurface severely damaged skin in high risk individuals, as a prophylactic measure, rather than a treatment, per se.
Topical fluorouracil (5-FU / Efudex).
This method may be very helpful in the management of selected patients with superficial basal cell carcinomas. A 5% topical ointment is applied daily to the affected area. Intense redness and weeping occurs after about 6 weeks and represents this represents the clinical end-point of treatment.
Interferon alfa (Aldara).
This is applied in a similar way to the above method. I have used this modality with excellent results on superficial BCC. My usual protocol is daily application Monday to Friday for 5 weeks. It is a rather expensive option but is usually better tolerated than 5FU treatment.
Photodynamic therapy (PDT).
Photodynamic therapy treats affected areas with a photosensitizer drug (applied topically as a cream) and then exposing the area to far blue light which “activates” the drug and results in cell death. It may be effective treatment for patients with superficial epithelial skin tumors.
Following treatment for basal cell carcinoma, patients should be clinically examined every 6 months for 5 years. Thereafter, patients should be examined for recurrent tumors or new primary tumors at yearly intervals.
Generally the prognosis is excellent. Neglected lesions with extensive infiltration may require radical ablative surgery, or may be irresectable. Of the patients who develop a basal cell carcinoma, 35% will develop a second primary basal cell carcinoma within the next 3 years and 50% at 5 years. Recurrence is a marker of significant epidermal damage and is a risk factor for both future SCC and melanoma. BCC spreads to other sites very, very infrequently – this is why the prognosis is so good.
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