Pathology is the study of the causes and consequences of a disease. A medical doctor that specializes in pathology is called a pathologist. Pathologists are experts at interpreting microscopic views of body tissues. It includes an examination of surgically removed organs, tissues (biopsy samples), bodily fluids and blood. The cellular pattern of tissue samples are observed under a microscope to help determine if a sample is infectious, non-infectious cancerous or non-cancerous (benign).

Pathologists specialize in a wide range of diseases including cancers. Main branches of pathology are the surgical pathology, cytopathology, and haematology. Surgical Pathology is the most significant and time-consuming branch of pathology with a primary focus on examining tissues with the naked eye and under a microscope for definitive diagnosis of diseases. Histological sections of tissue are processed for microscopic viewing using chemical fixation. Cytopathology is a branch of pathology that studies and diagnoses diseases on the cellular level. It is usually used to aid in the diagnosis of cancer, but also helps in the diagnosis of certain infectious diseases and other inflammatory conditions. Fine–needle aspiration (FNA) is a diagnostic procedure used to investigate lumps or masses. In this technique, a thin (23-25 gauge), hollow needle is inserted into the mass for the sampling of cells that, after being stained, will be examined under a microscope. Hematopathology or hemopathology is the study of diseases and disorders affecting blood cells, their production, and any organs and tissues involved in hematopoiesis, such as bone marrow, the spleen, and the thymus.