This chapter delves into various aspects of cancer, covering its diagnosis, screening, and treatment. Beginning with an introduction to the fundamentals of cancer, it presents an overview of cancer epidemiology and statistics, highlighting the prevalence and impact of the disease worldwide. Cancer screening methods are discussed next, emphasizing the importance of early detection in improving outcomes. The chapter then moves on to clinical assessment and physical examination techniques vital for identifying cancer signs and symptoms. Laboratory tests play a crucial role in cancer diagnosis, with detailed descriptions of various tests used to detect cancer markers. Imaging modalities such as X-rays, CT scans, MRI, and PET scans are also covered, showcasing their significance in visualizing tumors and guiding treatment. Biopsy and histopathological examinations are explained as definitive diagnostic tools, providing microscopic insights into tumor characteristics. The chapter further explores molecular and genetic testing, which offers personalized treatment options based on genetic mutations. In terms of treatment, the chapter outlines different surgical approaches and their indications, alongside discussing potential complications and the role of physical therapy in rehabilitation. Radiation therapy, including external beam radiation therapy and brachytherapy, is elaborated upon, followed by a discussion on managing its side effects through rehabilitation. Chemotherapy agents and their combinations, along with their side effects and related rehabilitation considerations, are detailed. The chapter also covers targeted therapies like monoclonal antibodies and tyrosine kinase inhibitors, emphasizing the importance of rehabilitation in managing these treatments. Lastly, immunotherapy, specifically immune checkpoint inhibitors, is discussed with a focus on the rehabilitation needs of patients undergoing such treatments. Overall, this comprehensive chapter provides a thorough understanding of cancer diagnosis, screening, and treatment modalities, underscoring the importance of rehabilitation in enhancing patient outcomes.