In the era of precision medicine, liquid biopsy has become an indispensable tool in research and clinical diagnostics. This innovative molecular approach offers significant benefits in managing cancers, such as melanoma, colorectal cancer, lung cancer, and, now, head and neck tumors. By addressing the challenges posed by tumor heterogeneity, liquid biopsy aligns seamlessly with precision medicine strategies, providing more accessible methods to detect and monitor genetic alterations in tumors. While biomarkers for head and neck tumors have been identified, integrating these markers into diagnostic workflows remains a challenge due to the complexities of current sampling techniques. Could liquid biopsy pave the way for a breakthrough in the diagnosis, monitoring, and treatment of patients with head and neck cancer? This review explores the expanding role of liquid biopsy in oncology, with a focus on its potential to revolutionize the management of head and neck malignancies. Liquid biopsy has become an integral part of diagnosis, classification, and prognostication of numerous cancers, namely, head and neck tumors. Liquid biopsy should work in concert with histological testing, imaging, surgery, and other diagnostic and therapeutic approaches, as each offers distinct advantages that together contribute to achieving the best possible patient outcomes.

Nitric oxide (NO) is a central regulator of cardiovascular function, influencing vascular tone, platelet activity, and inflammatory signaling. Despite decades of work defining its molecular pathways, translation into consistent clinical application has remained uneven, with findings across experimental, biomarker, and therapeutic studies often appearing inconsistent. Part of this variability reflects how NO behaves under different biological conditions. Its effects are shaped by where it is produced, how much is generated, and the biochemical environment in which it operates. Under some conditions, NO supports vascular homeostasis, while in others it contributes to oxidative and nitrosative stress, a pattern we refer to as the nitric oxide paradox. This review revisits commonly used NO-related biomarkers, including nitrate/nitrite (NOx), asymmetric dimethylarginine (ADMA), and 3-nitrotyrosine, and considers why their clinical interpretation remains inconsistent. It also examines the limitations of NO-based therapies, where short half-life, systemic exposure, and limited control over delivery continue to constrain outcomes. Rather than viewing these findings as conflicting, this article considers them as reflections of how NO signaling shifts across different physiological contexts. We organize NO signaling according to four interacting determinants: enzymatic source, magnitude and duration of production, cellular compartment, and the surrounding redox environment. Framing NO biology in this way may help explain variability in both diagnostic and therapeutic settings and clarify where current approaches remain limited.

Nitric oxide (NO) is a central regulator of cardiovascular function, influencing vascular tone, platelet activity, and inflammatory signaling. Despite decades of work defining its molecular pathways, translation into consistent clinical application has remained uneven, with findings across experimental, biomarker, and therapeutic studies often appearing inconsistent.Part of this variability reflects how NO behaves under different biological conditions. Its effects are shaped by where it is produced, how much is generated, and the biochemical environment in which it operates. Under some conditions, NO supports vascular homeostasis, while in others it contributes to oxidative and nitrosative stress, a pattern we refer to as the nitric oxide paradox.This review revisits commonly used NO-related biomarkers, including nitrate/nitrite (NOx), asymmetric dimethylarginine (ADMA), and 3-nitrotyrosine, and considers why their clinical interpretation remains inconsistent. It also examines the limitations of NO-based therapies, where short half-life, systemic exposure, and limited control over delivery continue to constrain outcomes.Rather than viewing these findings as conflicting, this article considers them as reflections of how NO signaling shifts across different physiological contexts. We organize NO signaling according to four interacting determinants: enzymatic source, magnitude and duration of production, cellular compartment, and the surrounding redox environment. Framing NO biology in this way may help explain variability in both diagnostic and therapeutic settings and clarify where current approaches remain limited.