It is well recognized that having one basal cell cancer means that you probably have a 50% chance of one day developing a second basal cell cancer. However the risk of future invasive skin cancer in patients with only squamous cell cancer in situ (the earliest stage of skin cancer) was not clear. Now a study has calculated that in patients with a history of squamous cell cancer in situ there is an over 15 x the risk of developing an invasive squamous cell cancer in the future. This reminds us that not only is it important to correctly treat all skin cancer but the subsequent follow up and surveillance in these patients is vital. In my practice, I suggest that all patients with a history of basal cell cancer or squamous cell skin cancer (including squamous cell cancer in situ) monitor their own skin with a self-exam every month and get a complete skin cancer screening exam from their dermatologist every 6 months.
Assessment of Cutaneous Squamous Cell Carcinoma (cSCC) In Situ Incidence and the Risk of Developing Invasive cSCC in Patients With Prior cSCC In Situ vs the General Population in the Netherlands, 1989–2017
JAMA Dermatol 2020 Jul 01;[EPub Ahead of Print], S Tokez, M Wakkee, M Louwman, E Noels, T Nijsten, L Hollestein