The cancer anorexia-cachexia syndrome (CACS) is considered a multifactorial syndrome that leads a general decline of the cancer patient conditions, prognosis and survival, and characterized by progressive loss of body mass and functional impairment, due to marked energy metabolism imbalance and immunological disorders. It is the cause of death in almost one out of five advanced cancer patients. CACS is also accompanied with loss of quality of life, reduced response and tolerance to anticancer therapies and affected outcome. This condition arises by acute-chronic inflammation, hypercatabolism and resulting in an increased energy expenditure, anorexia and negative caloric balance. Although the international scientific community has reached some important findings in last years regarding CACS, a precise definition agreement for CACS in order to a precise patients assessment is still lacking. In light of the advances in pathogenesis and evaluation of CACS, as well as those reached in the therapy, this review aims to draft a list of key points that could be useful for the oncologist to recognize the different signs and symptoms of this syndrome, in order to evaluate and stage the cancer patients in attempt to target an early multimodal pharmacological-nutritional treatment strategy to improve his outcome and his quality of life.