"good" steak, for instance is marbled. i'm not sure how you can get that with uncontrolled growth of one type of tissue. best case scenario you grow a huge chunk of cancerous muscle, and grind it with fat to make ground beef.

Tumours are typically poorly organised tissues with areas of dead cells (necrosis) and very fibrous reactions from surrounding tissue (desmoplastic reaction). A steak made out of a large tumour would look patchy, and have areas of cheesy looking dead tissue that will belch yellow goo when you touch it. It will also be very chewy. Additionally, most cancers develop in tissues that are the equivalent of the gizzards, whereas most human meat consumption is muscle tissue.