The field of pathology is a medical specialty that is concerned with the study of the causes and effects of a disease or injury. The diagnosis of a disease may be based on the gross, immunologic, chemical, microscopic and molecular examination of tissues, organs and whole bodies. A diagnosis can also be established with a laboratory analysis of blood, urine and tissue extracts or homogenates. The visual presentation of a body fluid is the first indication of the underlying condition. A microscopic examination in which techniques of cytochemistry, immunofluorescence, FISH and immunocytochemistry are utilized is used to determine whether the fluid is normal or infectious, tumoral or inflammatory. Such tests also allow the specification of the causal infectious agent. Certain diseases may require diagnosis at the cellular level, such as certain inflammatory and infectious diseases, cancer, diseases involving sterile body cavities and thyroid lesions. This book discusses the fundamentals as well as modern approaches of diagnostic pathology. It unfolds the innovative aspects of pathology which will be crucial for the progress of this field in the future. This book aims to equip students and experts with the advanced topics and upcoming concepts in this area.