Yes, the CT may show cancer if it's in the skin. It did with me last year with a metasteses was found in the epilithical layer of skin. CT scans can detect tumors as low as 1cm, maybe smaller in some cases. A PET/CT as low as 5mm, even smaller, and again with me last month with a nodal metastases that was only 3x7mm.
Good luck with surgery, and hope you get some answers, and better if no cancer is found.