skin cancer

Introduction

95% and 99% of skin cancers in Australia are caused by exposure to the sun
the average age at diagnosis for non-melanoma skin cancers in Australia is 76 years old
melanomas and BCCs can occur in young adults

this is due to a number of factors:
- southern hemisphere summers are closer to the sun giving 7-10% more UV strength
- relatively low air pollution allows more UV through
- generally fewer cloudy days allows more UV through
- higher sun angle as many areas (especially Queensland) are closer to the equator thus greater sun strength
- slightly thinner ozone layer in southern states thus less UV protection
- high degree of reflected sunlight from sand, water and light colored surfaces
the generally warmer weather means we tend to be more outdoors and exposed for longer periods
you can get severely sunburnt in Queensland even on cloudy days
you can get severely sunburnt anywhere in Australia in summer even if you feel cold due to a cool wind
perhaps the biggest risks for future skin cancers are the cumulative UV exposures in early life up to middle age

70% of non-melanoma skin cancers
begins in the lower layer of the epidermis
generally slow growing local spreading cancers which rarely metastasize
- may be a pearly lump
- may be a scaly, dry area that is shiny and pale or bright pink in colour
most commonly develops on parts of the body that receive high or intermittent sun exposure (head, face, neck, shoulders and back)
excisional Rx generally requires 3 to 5 mm margin of normal skin around the tumour
types:
- Nodular BCC
  - these are the most common types and are the classic shiny pearly edged ones mainly on the face and may have central ulceration and blood vessels over the surface
- Superficial BCC
  - in younger adults esp. on upper trunk and shoulders
  - slightly scaly, irregular plaque with multiple microerosions and thin, translucent rolled border
- Morphoeic BCC
  - usually mid-facial
  - waxy, scar-like with indistinct borders
  - wide and deep subclinical extension and may infiltrate nerves
  - higher recurrence rates
  - usually managed best with Moh's surgery
- Basosquamous carcinoma
  - mixed BCC/SCC with infiltrative growth and more aggressive behaviour

less common than BCC accounting for 30% of non-melanoma skin cancers
begins in the upper layer of the epidermis
usually appears where the skin has had most exposure to the sun (head, neck, hands, forearms and lower legs)
generally grows quickly over weeks or months
suggestive features:
- thickened red, scaly spot
- rapidly growing lump
- looks like a sore that has not healed
- may be tender to touch

includes solar keratoses, Bowenoid keratosis and squamous cell carcinoma in-situ (Bowen's disease)
may develop into non-melanoma skin cancers
rare for a solitary actinic keratosis to evolve to squamous cell carcinoma (SCC) ¹⁾
the risk of SCC occurring at some stage in a patient with more than 10 actinic keratoses is thought to be about 10 to 15%
- a tender, thickened, ulcerated, or enlarging actinic keratosis is suspicious of evolution to SCC
the number and severity of actinic keratoses can be reduced by taking nicotinamide (vitamin B3) 500 mg twice daily ²⁾

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