In some cases certain pathological subtypes of cancer or tumour tests (immunohistochemistry or tumour genetic tests) may suggest an underlying inherited cancer predisposition.

Medical genetic testing is not routinely required for keratinocyte cancer. Only a minority of patients will require genetic testing.

Anyone diagnosed with multiple skin cancers should have a detailed personal and family cancer history taken. Consult relevant guidelines to determine if referral to a familial cancer service is appropriate.

While most keratinocyte cancers develop through sun exposure, several genes and hereditary syndromes increase the risk of keratinocyte cancer development (NCI 2020).

Genetic factors associated with an increased risk of developing BCC include:

• Gorlin’s syndrome, which affects the PTCH1 and PTCH2 genes.

Hereditary syndromes associated with an increased risk of developing SCC include:

• xeroderma pigmentosum
• oculocutaneous albinism
• epidermolysis bullosa
• Fanconi anaemia
• Bloom syndrome
• Chédiak-Higashi syndrome
• epidermodysplasia verruciformis
• Griscelli syndrome
• Hermansky-Pudlak syndrome
• Ferguson-Smith syndrome
• Rothmund-Thomson syndrome
• Werner syndrome.

A familial cancer service assessment can determine if genetic testing is appropriate. Genetic testing is likely to be offered when there is at least a 10 per cent chance of finding a causative ‘gene error’ (pathogenic gene variant; previously called a mutation). Usually testing begins with a variant search in a person who has had cancer (a diagnostic genetic test). If a pathogenic gene variant is identified, variant-specific testing is available to relatives to see if they have or have not inherited the familial gene variant (predictive genetic testing).

Medicare funds some genetic tests via a Medicare Benefits Schedule (MBS) item number but most are not. Depending on the personal and family history, the relevant state health system may fund public sector genetic testing.

Pre-test counselling and informed consent is required before any genetic testing. In some states the treating team can offer ‘mainstream’ diagnostic genetic testing, after which referral is made to a familial cancer service if a pathogenic gene variant is identified. The familial cancer service can provide risk management advice, facilitate family risk notification and arrange predictive genetic testing for the family.

Visit the Centre for Genetics Education website for basic information about cancer in a family.