Histopathology

Histopathology is a specialized branch of medicine concerned with the analysis of bodily tissues that are suspected of being involved in disease processes. Although the terms "histopathology" and "histology" sometimes are used interchangeably, there are subtle but important differences between the two fields. Histology focuses on the general study of tissue structures, healthy and otherwise, while histopathology is specifically concerned with diseased tissues.

Although many diseases and medical disorders can be detected with histopathological techniques, the field is best known for its applications in the diagnosis of cancer. Histopathological examinations also can be performed post-mortem as part of an autopsy to determine or generate clues regarding an individual's cause of death. In other cases, histopathologists assist surgeons during live operations by providing an on-the-spot diagnosis to inform the surgeon's choice of how to proceed.

Background

The word "histopathology" is comprised of three distinct root parts, all of which are derived from Greek: histos, meaning "tissue," pathos, meaning "suffering" or "disease," and logia, meaning "study" or "the study of." The term first appeared in scientific circles in 1896.

Histopathology is closely linked to three other branches of medical science: pathology, histology, and cytopathology. Pathology is the general study of diseases and disease processes, on both the micro and macro levels. Histology is the general study of tissues, and the field covers both healthy and abnormal tissues in animals and plants. Cytopathology is a specialized branch of medicine concerned with anatomical pathology and specifically with diagnosing diseases by examining cells harvested from bodily fluids and secretions. Histopathologists, on the other hand, deal exclusively with solid tissues, which typically are obtained using one of two methods. Histopathologists may examine large tissue specimens, including whole or partial organs extracted during surgery or an autopsy. Alternately, they may be given smaller sections of frozen tissue obtained via a biopsy. These tissues typically require microscopic examination to determine if disease processes are at work.

Diagnosing diseases based on visual examination of tissue samples has long been a feature of modern medicine, but the field of histopathology made several noteworthy advancements over the course of the 1980s and early 1990s. New histopathological processes and techniques, including immunohistochemistry, bone pathology, and flow cytometry, developed and matured during this time. Immunohistochemistry is an advanced diagnostic technique that studies how immune system elements such as antigens and antibodies interact with tissues on a microscopic level. Bone pathology specializes in detecting and analyzing the ways in which disease processes affect bones and bone structures. Flow cytometry suspends cells in fluid so that they can be passed through a diagnostic tool that uses electronic technologies to detect clues known as "biomarkers," which convey information about underlying cellular processes. The 1980s and 1990s also saw the development and use of new image analysis techniques and technologies, many of which continue to form the basis of histopathological analysis methods currently in use.

Overview

For the most part, the histopathological analysis of tissues and tissue samples is carried out in laboratory settings, where histopathologists are presented with specimens for visual analysis and/or diagnostic testing. Histopathologists are able to diagnose diseases or disease processes by identifying the presence or absence of biomarkers and other indicators and by analyzing the structure and condition of the tissue itself.

In laboratory settings, histopathologists work exclusively with samples that have been frozen for the purposes of preservation. For live patients awaiting a diagnosis, these samples usually are obtained via a biopsy. A biopsy involves the surgical or nonsurgical extraction of a small tissue sample, which is then frozen and sent to a laboratory to determine whether or not disease processes are at work and, if so, to what extent they have progressed. For deceased patients, histopathologists assist with autopsies by analyzing tissue samples to determine the presence or absence of diseases or disease processes that may have caused or contributed to the patient's death. The branch of histopathology used in autopsy analysis is known as forensic histopathology. Other histopathology specializations include diagnostic histopathology, pediatric histopathology, and perinatal histopathology. Currently, there is a growing trend toward sub-specialization within the broader field itself.

Occasionally, histopathologists assist surgeons while they perform operations, especially in cases involving cancer. In some cases, surgeons must make on-the-spot decisions with regard to removing tissues that are suspected of containing cancerous masses, and it is not always clear whether or not the excision of a particular organ, bodily system, or tissue mass is required. To increase his or her chances of making the right decision, the surgeon can remove a sample from the suspect tissue mass and have it sent to an on-call histopathologist for immediate analysis. The histopathologist then can confirm whether or not the tissue sample shows markers of disease processes, enabling the surgeon to proceed accordingly with the rest of the operation.

Some histopathologists choose to specialize in particular types of tissue analysis. For example, some histopathologists specialize in analyzing tissue samples taken from patients suspected of suffering heart attacks or other severe cardiac events at an unusually young age. Others specialize in diagnosing particular forms of cancer such as oral cancers, lung cancers, and pancreatic cancers.

Histopathology is considered a laboratory-based specialization, and most histopathologists have little or no interpersonal contact with patients. Given that many histopathologists are involved in the detection and diagnosis of cancer, they play a very important frontline role in the development and application of cancer-screening techniques. Histopathologists can detect biomarkers indicating the presence of pre-cancerous processes, which can help doctors and patients take aggressive action to prevent further progression of disease. Histopathologists also provide critical insights with regard to the grading and staging of cancer tumors, helping the patient's caregivers formulate targeted strategies for future interventions and management.

Bibliography

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