Cytology
Cytology
Cytology is the branch of biology that studies cells, the building blocks of life. The name for this science is translated from kytos, the Greek term for”cavity.“Cytology’s roots travel back to 1665, when British botanist Robert Hooke, examining a cross-section of cork, gave the spaces the name”cells, “meaning”little rooms“or”cavities.”
Cytology’s beginnings as a science occurred in 1839 with the first accurately conceived cell theory. This theory maintains that all organisms plants and animals alike—are comprised of one or more like units called cells. Each of these units individually contain all the properties of life, and are the cornerstone of virtually all living organisms. Further, cell theory states that hereditary traits are passed on from generation to generation via cell division. Cell division generally has a regular, timed cyclical period during which the cell grows, divides, or dies. Virtually all cells perform biochemical functions, generating and transmitting energy, and storing genetic data carried down to further generations of cells. Cytology differs from its cousin, pathology, in that cytology concentrates on the structure, function and biochemistry of normal and abnormal living cells. Pathology pursues changes in cells caused by decay and death.
Cells can vary dramatically in size and shape from organism to organism. While plant and animals cell diameters generally average between 0.00036-0.00108 in (10-30 mm), sizes can range from a few thousand atomic diameters for single-celled microorganisms, all the way up to 20-in (50-cm) diameters for the mono-cellular ostrich egg. Cell structures also differ between advanced single-celled and multicellular organisms (plants and animals) and more primitive prokaryotic cells (e.g., bacteria). Plant cells are the most representative of a prototypical cell, as they have a nucleus, cell membrane and cell wall. Animal cells, on the other hand, lack a formalized cell wall, although they contain the former two. Prokaryote cells (e.g., bacteria) are unique in that they lack a nucleus and possess no membrane-enclosed organelles. Exceptions to the cell theory include syncytial organisms (e.g., certain slime molds and microscopic flatworms) without cellular partitions; however, they are derived secondarily from organisms with cells via the breakdown of cellular membranes. Finally, the number of cells within an organism can range from one for organisms like an amoeba, to 100 trillion cells for a human being.
Cytology has greatly benefited from the electron microscope, which reveals internal and external cell dynamics too small to be monitored by traditional optical microscopes. Also, fluorescence or contrast microscopy with more traditional visual observation equipment enables the cell substance to be revealed when a specific cell material is stained with a chemical compound to illuminate specific structures within the cells. For example, basic dyes (e.g., hematoxylin) illuminate the nucleus, while acidic dyes (e.g., eosin) stain the cytoplasm (the cellular material within the membrane (excluding the nucleus). Finally, newer techniques including radioactive isotopes and high-speed centrifuges have helped advance cytology.
Cytological techniques are beneficial in identifying the characteristics of certain hereditary human diseases, as well as in plant and animal breeding to help determine the chromosomal structure to help design and evaluate breeding experiments. A far more controversial discussion deals with the role of cytology as it relates to cloning.
Over time, cytology’s prominence as a separate science has diminished, integrating into other disciplines to create a more comprehensive biological-chemical approach. Associated disciplines include cytogenetics (study of behavior of chromosomes and genes relating to heredity) and cytochemistry (study of chemical contents of cells and tissues).
Cytology
Cytology
Definition
Cytology is the examination of individual cells and small clusters of cells, and may be used for the diagnosis and screening of diseases, including cancers. Cytology can also be referred to as cytopathology.
Purpose
Diagnostic tests are used to detect a disease in individuals who have signs, symptoms, or some other abnormality that is indicative of disease. A screening test identifies those who might have a certain disease, sometimes before they develop any symptoms, but does not absolutely prove that disease is present. If a screening test is positive, a diagnostic test can be used as follow-up to verify the diagnosis.
Precautions
Procedures to gather cells for cytology are often less invasive than other forms of biopsy , and therefore may cause less discomfort, be less likely to result in serious complications, and cost less to perform. In some situations, however, where a piece of tissue is removed rather than individual cells, a different type of biopsy may be required to confirm the cytologic diagnosis.
Description
Samples for cytology can be obtained in more than one way. Fine needle aspiration (FNA) is a type of biopsy in which tumor samples are taken through thin needles.
Scrape or brush cytology is another technique in which cells are scraped or brushed from the organ or tissue being tested. Samples from the esophagus, stomach, bronchi (breathing tubes that lead to the lungs), and mouth can be obtained using this procedure.
How a cytology sample is processed depends on what type of sample it is. A doctor can smear a sample directly on a glass microscope slide. The slide is then stained and viewed by a cytopathologist. In other cases, the fluid is concentrated before being smeared and stained on a slide. This is especially useful for dilute samples such those from body cavities.
Most routine cytology results are available one or two days after the sample is received in the laboratory. There are many reasons why some results take longer to return, such as if special stains are required to confirm a diagnosis.
Preparation, Aftercare, and Risks
Because this analysis is performed on cells that had been already gathered during initial diagnostic procedures, there is no additional preparation, aftercare, or risks for the patient. The only procedure, aftercare, or risks to note would be those associated with the sample collection itself.
Normal results
A cytopathologist examines and identifies the normal and abnormal cells on the slide using a microscope.
Abnormal results
A pathologist reviews the cells identified as abnormal to decide on a diagnosis.
See Also Biopsy; Pap test
Resources
PERIODICALS
Dahlstrom, Jane E., Gillian M. Langdale-Smith, and Daniel T.James. "Fine Needle Aspiration Cytology of Pulmonary Lesions: A Reliable Diagnostic Test" Pathology 33 (2001): 13-16.
ORGANIZATIONS
American Cancer Society. 1599 Clifton Road NE, Atlanta, GA30329. (404) 320-3333. <http://www.cancer.org>.
American Society for Clinical Pathologists (ASCP). 2100 West Harrison Street, Chicago, IL 60612. (312) 738-1336. <http://www.ascp.org.>.
American Society for Cytopathology (ASC). 400 West 9th Street, Suite 201, Wilmington, DE 19801. (302) 429-8802. <http://www.cytopathology.org.>.
College of American Pathologists (CAP). 325 Waukegan Road, Northfield, IL 60093. (800) 323-4040. <http://www.cap.org>.
International Academy of Cytology (IAC). 1640 East 50th Street, Ste. 20C, Chicago, IL 60615-3161. (773) 955-1406. <http://www.cytology-iac.org>.
Laura Ruth, Ph.D.
KEY TERMS
Biopsy
—Removing tissue from living patients for a diagnostic examination.
Cytology/cytopathology
—The study of cells or cell types.
Fine needle aspiration
—Removal of tissue or suspensions of cells using a small needle.
Pap smear
—A common cytology test used to screen for malignant and premalignant changes of the cervix.
QUESTIONS TO ASK THE DOCTOR
- What is a cytology test?
- How accurate is a cytology test?
- How long will it take to get cytology test results?
Cytology
Cytology
Cytology is the branch of biology that studies cells, the building blocks of life. The name for this science is translated from kytos, the Greek term for "cavity." Cytology's roots travel back to 1665, when British botanist Robert Hooke, examining a cross-section of cork , gave the spaces the name "cells," meaning "little rooms" or "cavities."
Cytology's beginnings as a science occurred in 1839 with the first accurately conceived cell theory. This theory maintains that all organisms plants and animals alike are comprised of one or more like units called cells. Each of these units individually contain all the properties of life, and are the cornerstone of virtually all living organisms. Further, cell theory states that hereditary traits are passed on from generation to generation via cell division . Cell division generally has a regular, timed cyclical period during which the cell grows, divides, or dies. Virtually all cells perform biochemical functions, generating and transmitting energy , and storing genetic data carried down to further generations of cells. Cytology differs from its cousin, pathology , in that cytology concentrates on the structure, function and biochemistry of normal and abnormal living cells. Pathology pursues changes in cells caused by decay and death.
Cells can vary dramatically in size and shape from organism to organism. While plant and animals cell diameters generally average between 10–30 micrometers (0.00036–0.00108 inches), sizes can range from a few thousand atomic diameters for single-celled microorganisms , all the way up to 20–in (50–cm) diameters for the monocellular ostrich egg. Cell structures also differ between advanced single-celled and multicellular organisms (plants and animals) and more primitive prokaryotic cells (e.g., bacteria ). Plant cells are the most representative of a prototypical cell, as they have a nucleus, cell membrane and cell wall. Animal cells, on the other hand, lack a formalized cell wall, although they contain the former two. Prokaryote cells (e.g., bacteria) are unique in that they lack a nucleus and possess no membrane-enclosed organelles. Exceptions to the cell theory include syncytial organisms (e.g., certain slime molds and microscopic flatworms ) without cellular partitions; however, they are derived secondarily from organisms with cells via the breakdown of cellular membranes. Finally, the number of cells within an organism can range from one for organisms like an amoeba , to 100 trillion cells for a human being.
Cytology has greatly benefitted from the electron microscope , which reveals internal and external cell dynamics too small to be monitored by traditional optical microscopes. Also, fluorescence or contrast microscopy with more traditional visual observation equipment enables the cell substance to be revealed when a specific cell material is stained with a chemical compound to illuminate specific structures within the cells. For example, basic dyes (e.g., hematoxylin) illuminates the nucleus, while acidic dyes (e.g., eosin) stain the cytoplasm (the cellular material within the membrane (excluding the nucleus). Finally, newer techniques including radioactive isotopes and high-speed centrifuges have helped advance cytology.
Cytological techniques are beneficial in identifying the characteristics of certain hereditary human diseases, as well as in plant and animal breeding to help determine the chromosonal structure to help design and evaluate breeding experiments. A far more controversial discussion deals with the role of cytology as it relates to cloning.
Over time , cytology's prominence as a separate science has diminished, integrating into other disciplines to create a more comprehensive biological-chemical approach. Associated disciplines include cytogenetics (study of behavior of chromosomes and genes relating to heredity) and cytochemistry (study of chemical contents of cells and tissues).
cytology
cy·tol·o·gy / sīˈtäləjē/ • n. the branch of biology concerned with the structure and function of plant and animal cells.DERIVATIVES: cy·to·log·i·cal / ˌsītlˈäjikəl/ adj.cy·to·log·i·cal·ly / ˌsītlˈäjik(ə)lē/ adv.cy·tol·o·gist / -jist/ n.
cytology
—cytological adj.