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Significant changes in diet, environment, and population increase gastrointestinal cancer morbidity. A growing number of novel biomarkers and underlying mechanisms are being elucidated, some of which may even conflict with assumptions of past decades. Therefore, collecting recent findings on novel diagnostic/prognostic factors, biomarkers, and/or risk factors in gastrointestinal cancers is a prerequisite for a better understanding of the disease. Despite remarkable progressions in surgical treatments and chemotherapies, the prognosis of gastrointestinal cancer is far from satisfactory due to the high occurrence of drug resistance. Based on the identification of novel biomarkers as well as their underlying mechanisms, targeted drug development will provide significant complementary therapeutic effects to conventional chemoradiotherapies. High-throughput methods such as next-generation sequencing on RNA level and mass spectrometry on protein/lipid/metabolite level serve as efficient strategies for biomarker identification and drug development. This Research Topic aims at presenting recent advances on gastrointestinal cancer biomarkers and their underlying functional mechanisms, providing a better understanding of carcinogenesis, tumor progression, tumor relapse, as well as drug resistance. This will subsequently contribute to the development of novel therapeutic interventions targeting gastrointestinal cancers, thus improving patients' outcomes.

This book aims to examine all immunohistochemical and molecular pathological biomarkers that can be useful and effective in patient diagnosis, prognosis and treatment decision, especially when faced with a carcinoma of unknown primary. For this purpose, epithelial malignancies of all systems and related biomarkers are examined one by one, and to look at the subject through the metastatic regions window, biomarkers that can be used to determine the primary focus for carcinomas seen in the areas most frequently metastasized are emphasized. With this bi-directional perspective, the reader is able to find biomarkers of any type of carcinoma on a system basis, as well as access to which biomarkers can be used when faced with a metastatic carcinoma. The importance of biomarkers in patient follow-up and treatment is also conveyed through the clinician's eye, and so biomarkers are handled with a holistic approach in all aspects. This book primarily targets pathologists, as well as clinicians (oncologists and surgeons) who manage cancer patients.

More and more medical centers are now combining high-resolution CT scans well with deep learning and artificial intelligence for lung cancer screening, resulting in significantly improved diagnostic sensitivity. Furthermore, the increased molecular alterations in lung cancer were demonstrated not only in tumor tissue, but also in other body organs. For example, circulating tumor DNA combined with next-generation sequencing is now becoming a popular method for lung cancer diagnosis and therapeutic monitoring. Therefore, the first focus of this topic is on such achievements in early diagnosis of lung cancer, especially non-invasive tests such as liquid biopsy.