Roscher I, et al. - Population-based data were used to assess the effect of risk factors for metastasis and to evaluate the validity and usefulness of 4 staging systems (the American Joint Committee on Cancer, 7th edition [AJCC 7] staging system, the staging system used by Breuninger et al., the Brigham and Women’s Hospital [BWH] staging system, and the AJCC, 8th edition [AJCC 8] staging system) for cutaneous squamous cell carcinoma (cSCC). The 4 current staging systems for cSCC were shown to be unsatisfactory in identifying non-selected cSCC patients at high risk for metastasis. The system used by Breuninger provided the best results.