Cancer and Alzheimer’s disease (AD) present an inverse relationship. The key distinctions between the conditions include the expression of TREM2 and the increase in inflammation: in AD, there is elevated TREM2 expression and inflammation, while these factors vary depending on the type of cancer. In addition, tumor and neural cells respond differently to oxidative stress: In AD, oxidative stress impairs protein translation, increases amyloid beta (Aβ) oligomerization, and leads to neurotoxicity, while in cancer, oxidative stress activates mechanisms to prevent cell death. A fundamental component to tumor development is angiogenesis; of note, the tau protein acts as a significant inhibitor of this process. Both conditions also share similarities, such as regulation of the proteins beclin-1, Rb, p53, p21, p27, PTEN, BRAF, phosphorylated ERK, and PIN1. They also share risk factors like insulin resistance, chronic inflammation, metabolic changes, obesity, type 2 diabetes mellitus, and aging. Based on the presented information, there is an inverse relationship between cancer and AD, and understanding these opposing mechanisms may provide insights into aspects that have yet to be elucidated and potential therapeutic strategies. Nevertheless, it is essential to explore the common mechanisms of these diseases to determine their role in their differentiation.