The root cause can be different per type of cancer, see for example the landmark TCGA/PCAWG paper: https://www.nature.com/articles/s41586-020-1969-6 https://ww

The root cause can be different per type of cancer, see for example the landmark TCGA/PCAWG paper: https://www.nature.com/articles/s41586-020-1969-6 https://www.nature.com/articles/s41586-020-1969-6 Figure 2 shows the different mutations present in cells in a variety of cancers carry. These genes have a variety of functions. The DNA of cancer cells from different tumor types is different, and TP53, the gene featured in OP, is never mutated in some cancer types. In the end the discussion is a little semantic (what defines a different disease), but if the prognosis, treatment, and molecular mechanisms behind different types of cancers are different, I would consider it fair to consider them different diseases.