A new non-invasive and potentially inexpensive frontier in the diagnosis of 
cancer relies on the detection of volatile organic compounds (VOCs) in exhaled 
breath samples. Breath can be sampled and analyzed in real-time, leading to 
fascinating and cost-effective clinical diagnostic procedures. Nevertheless, 
breath analysis is a very young field of research and faces challenges, mainly 
because the biochemical mechanisms behind the cancer-related VOCs are largely 
unknown. In this review, we present a list of 115 validated cancer-related VOCs 
published in the literature during the past decade, and classify them with 
respect to their "fat-to-blood" and "blood-to-air" partition coefficients. These 
partition coefficients provide an estimation of the relative concentrations of 
VOCs in alveolar breath, in blood and in the fat compartments of the human body. 
Additionally, we try to clarify controversial issues concerning possible 
experimental malpractice in the field, and propose ways to translate the basic 
science results as well as the mechanistic understanding to tools (sensors) that 
could serve as point-of-care diagnostics of cancer. We end this review with a 
conclusion and a future perspective.