The Early Treatment of Skin Cancer

Besides lung cancer, skin cancer is one of the most preventable types of cancer there is.

There are predominantly three forms of skin cancer:-

• Squamous cell carcinoma
• Basal cell carcinoma
• Melanoma

Squamous cell carcinoma

This is the second most common type of skin cancer.

Risk factors associated with squamous cell carcinoma

• Exposure to the sun: cutaneous squamous cell carcinoma is caused by cutaneous DNA damage by constant exposure to the sun.
• Immunosuppression as a result of chemotherapy or organ transplantation is an important cause of squamous cell carcinoma. This leads to increase in susceptibility of the keratocytes to infection particularly by viruses like HPV subtypes 5 and 8
• Other risk factors include industrial carcinogens like tars and oils, chronic ulcers. Draining osteomyelitis, intake of tobacco in any form, betel nut chewing, etc can also lead to squamous cell carcinoma.
• Studies on genetics of squamous cell carcinoma have found high correlation with p53 mutation particularly, in Caucasians.
• Patients with xeroderma pigmentosum are also susceptible to squamous cell carcinoma. exposure to UV light damages the protective functions of p53. The damaged p53 is repaired by error- prone mechanisms causing mutations.

Basal cell carcinoma

This is the most common skin cancer. It is slow growing in nature, rarely invasive in character and occurs from exposure to sunlight. These tumors are often presented as papules containing dilated subepidermal blood vessels. These tumuors rarely metastasise. These are also known by the name of rodent ulcers.

• Basal cell carcinoma occurs in association with Gorlin syndrome or Nevoid Basal Cell carcinoma syndrome. These tumors occur before the age of 20 years. The genes that are associated with this include (located on chromosome 9q) is PTCH. The PCTH gene encodes a protein for sonic hedgehog gene (SHH).
• PCTH mutations occur in 30% of sporadic basal cell carcinomas. In 40 to 60% of basal cell carcinomas mutations in p53 occur.
• The prevelance of skin cancer is South Africa is quite high. The South African Melanoma advisory board provides information about symptoms and treatment of Melanoma. Click here.

Melanoma

This another form of skin cancer, if not diagnosed early becomes fatal. Melanomas are aggressive form of tumour that metastasise and are resistant to any form of therapy. At diagnosis, melanomas measure greater than 10mm in diameter. The most consistent clinical signs are changes in colour, pigmentation and size.

Prognostic factors

A tumour is considered to be of a favourable prognosis when the depth of the tumor is less than 1.7mm, no mitoses is present, response of the tumour infiltrating lymphocytes is present, absence of regression, female, location of the tumour on extremity.

Predisposing factors

Genetic correlation:

It is said that 10 to 15% of the melanomas are of familial origin. Genes responsible for familial melanomas include mc1r, asip, tyr. Both sporadic and familial melanomas present diminished activity of retinoblastoma tumor suppressor proteins. In 40% of autosomal dominated melanomas there is mutation of cdkn2 genes. Sporadic melanomas are also the result of aberrant increase in the levels of ras and pi3k/akt signaling, which are pathways of cell growth.

These molecular pathways may throw some light on the methods by which melanomas can be treated with treated with therapeutic agents that target the ras and pi3k/akt pathways as melanomas are resistant to conventional chemotherapy and radiation.