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Q1: I have a number of dysplastic moles on my back. In 2004 I had a medical photo taken so that I could keep an eye on them and when I noticed last August that two had grown a lot I went back to my GP who expressed concern and said I would have to have them removed. I asked him about mole scanning as I've had moles removed before and have found it painful but he said they give too many false positive results and he referred me to the hospital. However when I saw the specialist he just sent me to have another photo taken and said to come back if they continue to grow, having already told me off for not monitoring how quickly they had grown! They haven't grown since but I am not feeling reassured at all. Should I go back to the doctor or go ahead and have a mole scan? Name and address withheld.

A1: Thank you for your question which raises many important and interesting points. Not all moles are equally significant. Doctors are always on the look out for dysplastic, atypical moles. These dysplastic moles are usually present in greater numbers and larger than the ordinary common mole. They also have irregular indistinct borders and similarly a lack of uniformity in their colour. Even the contours of the dysplastic mole may be different from an ordinary common mole so that instead of being flat they may be raised, and not always uniformly raised. Any mole that has a ragged outline, irregular contours and colours excites suspicion and a very close check needs to be kept on it.

Although people who have multiple dysplastic moles are many times more likely to develop a melanoma, a malignant mole, the great majority will never have one that turns malignant. Unfortunately people who have dysplastic moles don't often have only one but as you do they have many moles that are larger than the common mole and less regular in outline and colour.

People with many dysplastic moles often find that they are having numerous biopsies, fortunately the majority turn out to be negative but it is not a risk that anyone can afford to take especially if the mole has changed in shape and colour and grown. Changes of this sort always need immediate investigation. A single dysplastic mole can be easily removed but when there are large numbers of them even if not changing in appearance and not giving rise to symptoms such as irritation, scaliness etc. it could be difficult to set about removing them all. Certainly anyone with dysplastic moles should be under the care of a dermatologist as the decision when to excise is one that needs great experience. Many dermatologists are now using specialised photographic and diagnostic technology services. In my opinion it is important that full body, photographic front and back skin surface photographs, which have to be of medical photographic standards, are taken regularly. Additionally a dermoscope or siascope to analyse the microscopic appearance of the individual mole and the skin around it is useful in deciding whether the mole needs excision. In London, as I explained in my piece in the Times 2 of Thursday, February 14 (The new way to check for skin cancer) there are several centres that provide this sort of service. The staff at the centres work very happily with GPs, oncologists and dermatologists.

Once a photographic base line of the moles' appearance has been established it is easy to spot change. As you will be all too well aware what we are looking for is changes in the nature of the mole or the appearance of a mole in a previously virgin skin. The changes you are looking for are changes in outline, shape, size, colour (especially a new black or red area) or a change in the feel of the mole so that it feels lumpy. Most melanomas are greater in diameter than the blunt end of a lead pencil, their colours are often mixed. Although usually, but not always, predominantly black in colour, there may be elements of light and dark brown, pink or red, grey or blue. Doctors are especially interested in the outline of the mole, they hope for regular distinct edge whereas the moles we are more worried about have irregular edges sometimes with small notches in the outline.

Q2: I read with interest you article in today's Times (14/2/08). I speak as a person who has had three Basal Cell Carcinoma's on my face and have a few quick questions on the subject, namely:

1. What are the common cancers caused by lack of vitamin D?

2. In summer, if we protect ourselves from the sun with clothing and sunscreen strong enough to keep out UVA and UVB rays, how do we absorb enough sunlight to get our vitamin D?

3. With regard to my husband, he has suffered from Polymorphic Light Eruption for 15 - 20 years and even UV treatment brings him out in a rash. Neverthless he has now learnt to live with it and never goes out in the sun without his hat, long sleeves, long trousers and a total sun block. This is a real pain as we both enjoy gardening, he his allotment and we are keen ramblers able to enjoy the countryside where we live (Devon) and on walking holidays. With all of the protection he needs, do you think he is storing up other problems for later on and does he need to be taking a calcium suppletment and if so how high a dose? Name and address withheld.

A2: Vitamin D helps protect, with emphasis on the word helps, against prostate and breast cancer and to a lesser extent ovarian, colon and probably lung cancer. Vitamin D deficiency is likely to be one of the factors related to the causation of other cancers and when these are studied more closely this relationship may well become obvious. Most cancers have several different factors that may play a part in their causation. Fortunately most people suffering from vitamin D deficiency do not develop cancer as a consequence, but a small minority will. Vitamin D deficiency may also cause osteoporosis as it prevents calcium absorption, it may exacerbate type 2 diabetes, make psoriasis worse and the lack of sunlight may be a factor in the occurrence of relapses in depression and schizophrenia.