Many patients inquire about the risk to other family members given that they have had a skin cancer. There is a definite familial association with all types of skin cancer, but the genetics is complicated. Families with an outdoor lifestyle or who have been residents in a very sunny area, will of course have an increased risk compared to the general population.

The skin colour is obviously familial in most cases. Fair skinned individuals are much more likely to develop all types of skin cancer than darkly skinned individuals. Appropriate family counselling must take these factors into account.

Nevoid basal cell carcinoma syndrome is a dominant condition where multiple basal cell carcinomas develop over a lifetime. Hundreds of basal cell carcinomas can develop before age 40. It is associated with hypertelorism and palmar pitting, as well as jaw cysts and other abnormalities. Xeroderma pigmentosum is another condition where there is incomplete DNA repair of UV damage, leading to the early development of all major types of skin cancer. This is evidenced by obviously accelerated photoaging of the skin in the teenage or early adult years, with the development of skin cancers shortly thereafter.

The most clinically significant genetic association is the dysplastic nevus syndrome. The tendency towards developing multiple dysplastic nevi can be inherited as an autosomal dominant trait. This is a common condition. A single dysplastic nevus does not imply the dysplastic nevus syndrome. A patient with an increased number of nevi, many of which are clinically atypical, is at risk for this syndrome. In addition to their personal risk of developing multiple melanomas, there is an increase of melanoma in first-degree relatives. Patients with a melanoma and dysplastic nevi, or simply multiple dysplastic nevi, should be advised to have first degree relatives reviewed in the context of that diagnosis.