Risk Factors and Clinicopathological Features for Developing a Subsequent Primary Cutaneous Squamous and Basal Cell Carcinomas

Simple Summary Patients with basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (SCC) often develop new keratinocyte carcinoma (KC), but information is limited on the frequency and timing of these subsequent tumors. This information is crucial to guide follow-up care. Given the significant clinical differences of the characteristic feature of individual skin cancer, estimation of the risk of a subsequent tumor should be estimating separately. The aim of our retrospective study was to assess risk factors for a subsequent skin cancer development. We demonstrated that patients with multiple tumors must be followed up carefully and for a long time. Moreover, we indicated the connection between the BCC subtype and increased risk for further KC development. BCC subtypes with an aggressive growth pattern predispose not only to increased risk for the recurrence but also are expected to be at an increased risk for a subsequent tumor. The non-invasive diagnosis, monitoring and follow up should be more comprehensive for those patients compared to low-risk BCC. Background: Patients with diagnosed keratinocyte carcinomas (KCs) have an increased risk of subsequent skin cancers development. Current studies indicate that patients with subsequent tumors should be followed up regularly. However, none of the studies indicate the connection between the specific subtypes and an increased risk for further KCs development. The study assesses the differences in the risk of developing a subsequent skin cancer after a previous diagnosis of KC, especially considering individual types of skin malignances, and identifies potential factors associated with an increased risk of new cutaneous tumor describing non-invasive diagnosis and monitoring. Methods: Pathology and medical records were examined to identify the characteristics of patients with multiple KCs diagnosed between 1999 and 2019. Results: The study group comprised 13,913 KCs occurring in 10,083 patients. Multiple KCs were observed in 2300 patients (22.8%). The analysis showed aggressive subtypes, multiple tumors, and male sex as significant prognostic factors. Conclusions: The most crucial risk factors for developing subsequent KC are being of a male gender, an aggressive tumor subtype, and previous history of multiple skin cancers. Basal cell carcinoma subtypes, such as infiltrative basosquamous, with aggressive growth patterns predispose not only to increased risk for the recurrence but are also expected to be at higher risk of subsequent KCs.