Send FeedbackWhat is anatomic pathology?
Anatomic (or anatomical) pathology is the branch of medicine that studies the effect of disease on the structure of body organs, both as a whole (grossly) and microscopically. The primary role of anatomic pathology is to identify abnormalities that can help to diagnose disease and manage treatment. Although one of the frequent uses of anatomic pathology is to help identify and manage various types of tumors or cancers, it is also valuable in evaluating other conditions, including kidney and liver diseases, autoimmune disorders, and infections, for example. In fact, in most hospitals, all tissue removed during surgery must be examined by a pathologist.
Anatomic pathology is somewhat different from clinical pathology (or laboratory medicine), which deals with the measurement of chemical constituents of blood and other body fluids (clinical chemistry), analysis of blood cells (hematology), and identification of microbes (microbiology), to name a few examples. While most of the tests described on this site would be categorized as clinical pathology, many are used in conjunction with anatomic pathology procedures. In fact, technical advances are blurring the distinctions between the two in many areas. Overlaps include, for example, flow cytometry, cytogenetics and molecular pathology, which can be performed on both tissue samples and blood or body fluid samples. Therefore, some knowledge of this branch of medicine may help you better understand the tests that your or a family member’s health practitioner may consider in diagnosing, monitoring, and treating a condition.
There are two main subdivisions within anatomic pathology:
- Histopathology, which involves examination of intact tissue from biopsy or surgery under the microscope. This is often aided by the use of special staining techniques and other associated tests, such as using antibodies to identify different components of the tissue.
- Cytopathology (cytology), which is the examination of single cells or small groups of cells from scrapings or aspiration of fluid or tissue under the microscope. A common cytology test is the cervical Pap smear. Technologists often screen preparations and report results but, in many cases, the pathologist gives the definitive diagnosis to the health care practitioner.
Anatomic pathologists are also involved in performing post-mortem examinations (autopsies). An autopsy may be performed after a person has died of an illness that could not, for whatever reason, be properly or fully diagnosed before death. The physician will seek consent from the family to have an autopsy performed. If the cause of death is suspicious or related to an illegal activity, the autopsy will be performed by a forensic pathologist. Consent from next of kin is not required for such medico-legal autopsies. (For more on this, see our information page on Forensic Pathology and Autopsies.)
Histopathology: Biopsies and Examination of Tissues
Histopathology involves the examination of sampled tissues under the microscope. These may be small pieces of tissue obtained from a part of the body using a technique called biopsy or samples taken from whole organs or parts of organs removed during surgery.
Most biopsies are small samplings of the area of the body in which disease is suspected. These are called “incisional” biopsies and additional surgery or treatment may be recommended after the diagnosis is made.
Other biopsies may include the entire affected area, such as a skin mole. These are called “excisional” biopsies and examination of the adjacent, uninvolved margins helps to verify that the affected area has been completely removed.
The pathology laboratory also receives large whole organs, or parts of organs, removed during surgery, such as a uterus after a hysterectomy, the large bowel after a colectomy, or an amputation of an arm or leg. These specimens are examined as a whole (grossly) for size, shape, color, and/or presence of any external abnormalities. Then, smaller samples are taken for definitive microscopic evaluation.
Tissue Preparation
Special Techniques
Cytopathology
Cytology is the study of individual cells and cytopathology is the study of individual cells in disease, although the two terms are often used interchangeably. Sampled fluid and/or tissue from a patient is smeared onto a slide and stained (see techniques below). This is examined under the microscope by an anatomic pathologist (cytopathologist) to look at the number of cells on the slide, what types of cells they are, how they are grouped together, and what the cell details are (shape, size, nucleus, etc.). This information is useful in determining whether a disease is present and what is the likely diagnosis.
Cytology is most often used as a screening tool to look for disease and to decide whether or not more tests need to be performed. A common example of screening would be the investigation of a cervical (Pap) smear. The health practitioner inserts a speculum into the vagina to directly view the cervix, which is gently scraped or swabbed. The cells obtained are either smeared onto a glass slide or rinsed into a liquid-based fixative and submitted to the laboratory for examination.
The cells are reviewed by a cytotechnologist, who can issue a negative report if no abnormal cells are seen. If any suspicious cells are identified, a cytopathologist reviews the case and makes a final diagnosis. Follow-up may include a colposcopy (use of a magnifying device to examine the cervix more closely) to determine if the abnormality is a pre-cancerous or cancerous lesion caused by human papilloma virus (HPV) or some other lesion and if biopsies need to be taken.
Most of the immunohistochemical, cytogenetic, and molecular techniques described for histopathology can also be applied to cytopathology.
Techniques
Anatomic Pathology Results and Reports
Like clinical pathology reports (see Deciphering Your Lab Report), anatomic reports include essential elements such as patient name, identification number, sample type, and source. The report usually includes some very technical medical terms, so it is advisable to review and discuss the report with the health practitioner and ask questions about anything that is not understood.
An anatomic pathology report typically includes the following five main sections:
- Specimen information—details the type of tissue or organ involved, where the sample was taken and how
- Diagnosis—this may appear at the beginning or the end of the report; it includes the specific findings, the final diagnosis from the pathologist. It may be very short and to the point or may include several lines of language, depending on the complexity of the case.
- Gross (obvious or macroscopic) description of the sample—describes the visible characteristics, those readily seen by the naked eye, including size, shape, weight, color and/or consistency
- Microscopic findings—this is often very detailed; it is what the pathologist sees under the microscope and includes size, shape, and type of cells seen. It may include several other specifics. For example, it may describe the characteristics of a tumor:
- Invasive or non-invasive—whether cancer has spread
- Grade—typically used only for cancers; describes how the abnormal cells compare to normal cells; low-grade cells look more like healthy cells while high-grade cells look more abnormal; this may be used to help determine the course of the disease (prognosis).
- Dividing cells—whether the cells seen are dividing, which may imply that the tumor is aggressive
- Margins—this describes the appearance of the tissue at the edges of the sample; margins may be clear, indicating that no cancerous cells are seen at the edges. If the margins are not clear, additional surgery may be needed to fully excise the tumor.
- Nearby lymph nodes—included if lymph nodes are removed at the time of the biopsy; notes whether cancer has spread to nearby lymph nodes; may be described as “node negative” (no cancer spread) or “node positive” (cancer spread to nodes).
- Stage—this information may be helpful in establishing the prognosis. The pathology report may only include information available to the pathologist or it may also include other information (such as whether the tumor has spread to other organs or areas of the body).
- Comments —includes anything else the pathologist wishes to convey about the examination; it may include results of specialized tests that might impact treatment; however, these may also be provided in a separate report.
Depending on the reason for the biopsy and the type of tissue examined, the report may include additional details within these sections or additional sections. As mentioned in the introduction, a frequent use of anatomic pathology is in the evaluation of cancers and there has been an attempt to standardize these types of anatomic pathology reports so that specific details can be more easily entered into databases that serve as a tumor registry. Each state has such a registry and the information is collected by the Centers for Disease Control and Prevention (CDC) so that researchers can evaluate trends in cancer prevalence as well as new approaches to treatment.
