Pathology is a branch of medical science that is focused on the study and diagnosis of disease. Clinical pathology involves the examination of surgically removed organs, tissues (biopsy samples), bodily fluids, and, in some cases, the whole body (autopsy). Aspects of a bodily specimen that may be considered include its gross anatomical make up, appearance of the cells using immunological markers and chemical signatures, as well as genetic studies and gene markers. Pathologists specialize in a wide range of diseases, including cancer, and the vast majority of cancer diagnoses are made by pathologists. The cellular pattern of tissue samples are observed under a microscope to help determine if a sample is cancerous or non-cancerous (benign). Our Residency Program trains candidates in the diagnosis of disease.
Pathology also includes the related scientific study of disease processes whereby the causes, mechanisms and extent of disease are examined. Areas of study include cellular adaptation to injury, necrosis (death of living cells or tissues), inflammation, wound healing, and neoplasia (abnormal new growth of cells), as well as specific disorders of the individual organ systems. Our research laboratories are focused on understanding the cellular abnormalities in disease, with the eventual goal of improving both diagnosis and treatment. Our Graduate Studies Program trains candidates in laboratory research on disease.
In 2024, the field of pathology is reaching new milestones with recent renaming of the Royal College recognized subspecialty from Anatomical Pathology to Diagnostic & Molecular Pathology – a shift that represents the progression of this field from a macroscopic/microscopic to molecular level understanding of human disease and precision medicine. This transformation highlights the position of pathology at the center of health science advancement and its expansion from a purely diagnostic discipline into a key driver of patient treatment and prognostication.
Surgical pathology
Surgical Pathology is the most significant and time consuming branch of pathology with a primary focus on examining tissues with the naked eye or under a microscope for definitive diagnosis of disease. Surgically removed specimens are received from sources such as small biopsies of skin, core biopsies for the diagnosis of cancer, and the operating room where tumours are removed. Surgical pathology involves macroscopic (gross) and microscopic (histologic) tissue analysis where the molecular properties of tissue samples are assessed by immunohistochemistry or other laboratory tests.
Histological sections of tissue are processed for microscopic viewing using either chemical fixation or frozen section. Frozen section processing involves freezing the tissue and generating thin frozen slices of the specimen which are mounted onto glass slides. Prior to viewing the tissue under a microscope, slides processed by chemical fixation or frozen section are either stained with chemicals or antibodies to reveal cellular components.
Autopsy is a highly specialized surgical procedure that is performed by a pathologist and consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present. The principal aim of an autopsy or post-mortem examination is to determine the cause of death, the state of health of the person before they died, and whether any medical diagnosis and treatment before death was appropriate.
Cytopathology
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. Cytopathology is generally used on samples of free cells or tissue fragments that spontaneously exfoliate or are removed from tissues by abrasion or fine needle aspiration, in contrast to histopathology, which studies whole tissues.
Molecular Pathology
Molecular Pathology is a relatively recent discipline that has achieved remarkable progress over the past decade. It emphasizes the study and diagnosis of disease through the examination of molecules within organs, tissues or bodily fluids. Many diseases such as cancer are caused by mutations or alterations in the genetic code of a person, and identification of specific hallmark mutations allows clinicians to classify a disease and choose the appropriate treatment. As a result, molecular analysis is leading the way towards personalized medicine by allowing us to predict a patient’s response to certain anti-cancer therapy based on their own genetic make-up. Molecular Pathology includes the development of molecular and genetic approaches to the diagnosis and classification of human tumours and also to design and validate predictive biomarkers for prognosis of the disease, and susceptibility of developing certain cancers in individuals. The high levels of sensitivity provided by molecular assays allows for the detection of very small tumours that are otherwise undetectable by other means, and will likely result in earlier diagnosis, improved patient care and better outcomes for survival.
Digital Pathology
Digital Pathology is an up-and-coming area of quantitative pathologic assessment involving slide digitization, novel imaging systems, whole-slide scanners, and artificial intelligence (AI)-based analysis. Not only can information be extracted that goes beyond human visual perception, images/data can be stored and shared for remote teaching, research, consultation, and diagnostics.