ctDNA in Cutaneous Squamous Cell Carcinoma

This study is examining whether a blood test that detects tumor DNA (called ctDNA) can help track the progress of treatment or detect cancer recurrence in people with skin squamous cell carcinoma that has certain high-risk features. **You may be eligible if...** - You have a surgically removable skin squamous cell carcinoma with nerve involvement or at least 2 high-risk features (such as tumor larger than 2 cm, recurrence, spread to lymph vessels, a weakened immune system, poorly differentiated cells, or deep invasion) - You have surgically removable cancer that has spread to nearby lymph nodes and you are not receiving pre-surgery treatment - OR you have skin squamous cell carcinoma that cannot be surgically removed and is receiving drug therapy before surgery **You may NOT be eligible if...** - Your cancer cannot be surgically removed (for the post-operative group) - You are already receiving systemic drug therapy (for the post-operative group) Talk to your doctor to see if this trial is right for you.