Here, we discuss the roles of HSF1 in influencing tumor growth via modulation of cells’ autonomous changes associated with transformation, such as cell growth and mitosis, cell death, senescence, aneuploidy, metabolism, and differentiation, as well as tissue-level changes in angiogenesis and altered expression of stromal factors, and how these relate to metastasis and resistance. The gene discussed is HSF1; the disease is neoplasm.