tumor (noun) An abnormal growth of tissue resulting from uncontrolled, progressive multiplication of cells and serving no physiological function; a neoplasm

'benign tumor' maybe some Salmon Lipomas with crackers and cheese.

Multicellular life naturally exists in a well-ordered matrix according to a rough plan, not a blob in a petri dish, and when it deviates too much from that plan we have various pejorative words for it and feel various health consequences as a result of disordered growths.

Tissue culture in general is more like cancer than not like cancer, even when using "non-cancerous" cell lines. But cancerous and "immortalized" cell lines are particularly useful in cell culture because they don't snuff themselves out. https://en.wikipedia.org/wiki/Immortalised_cell_line