You cannot positively know anything is skin cancer without which of the following?

To definitively diagnose skin cancer, a biopsy diagnosis is essential. A biopsy involves taking a small sample of the suspicious tissue and examining it under a microscope. This process allows medical professionals to identify cancerous cells accurately and determine the specific type of skin cancer.

While visual exams can detect unusual skin changes and might suggest the possibility of skin cancer, they cannot confirm it. Blood tests can assist in certain types of cancer diagnoses or staging but are not used to diagnose skin cancer specifically. A family history of skin cancer can provide important context or risk factors but does not serve as a diagnostic tool on its own. Thus, the different methods have their roles, but only a biopsy can provide the definitive diagnosis needed to confirm the presence of skin cancer.