Wednesday, December 29, 2010

The Cellular Diseases

From Wikipedia, the free encyclopedia

Cytopathology (from Greek κύτος, kytos, "a hollow"[1]; πάθος, pathos, "fate, harm"; and -λογία, -logia) is a branch of pathology that studies and diagnoses diseases on the cellular level. The discipline was founded by Rudolf Virchow in 1858. A common application of cytopathology is the Pap smear, used as a screening tool, to detect precancerous cervical lesions and prevent cervical cancer. It is generally used on samples of free cells or tissue fragments, in contrast to histopathology, which studies whole tissues.
Cytopathologic tests are often called smear tests because the samples are smeared over a microscope slide to be studied for any pathology. However, a smear test usually refers specifically to a Pap test, that is, a cervical smear. However, smear tests also include e.g. vaginal wet mount, that is, a vaginal smear. Different types of smear tests may also be used for cancer diagnosis. In this sense, it is termed a cytologic smear.[2]
Cytopathology is frequently, less precisely, called cytology, which means "the study of cells."[3]

Cell collection

Two methods of collecting cell data for analysis are:
A micrograph of an exfoliative cytopathology specimen (Pap test, Pap stain)
  1. Exfoliative Cytology – Cells are extracted from fluid shed into the body cavities. For example, in pleural fluid, ascitic fluid, or in the case of the Pap smear, cells scraped from the cervix.Not only from cervix but all region that lined with epithelium spontaneouslyshedding during renewal
  2. Fine Needle Aspiration Cytology or Needle aspiration biopsy – A needle attached to a syringe is used to aspirate (pull out) cells from lesions or masses in various organs of the body by either free drainage or application of negative pressure (suction). FNAC can be done directly on a mass in superficial regions like the neck, thyroid or breast; or it may be assisted by ultrasound or CAT scan. The technique is widely used in many countries. Being a skill dependent procedure, the success rate may vary. If performed by a pathologist alone, or as team with pathologist-cytotechnologist, the success rate of proper diagnosis is superior than when performed by a non-pathologist[4]. Fine needles are 23 to 27 gauge. Sometime a syringe holder may be used to facilitate using one hand to perform the biopsy while the other hand is immobilizing the mass. Imaging equipment such as a CT scanner or ultrasound may be used to assist in locating the region to be biopsied.
  3. The collection of cell via brushing (difference from exfoliative is that not spontaneous) or similar abrasive techniques

Parameters

The nucleus of the cell is very important in evaluating the cellular sample. In cancerous cells, altered DNA activity can be seen as a physical change in the nuclear qualities. Since more DNA is unfolded and being expressed, the nucleus will be darker and less uniform, larger than in normal cells, and often show a bright red nucleolus.
While the cytologist's primary responsibility is to discern whether cancerous or precancerous pathology is present in the cellular sample analysed, other pathologies may be seen such as:
  • microbial infections: parasitic, viral, and/or bacterial
  • reactive changes
  • immune reactions
  • cell aging
  • amyloidosis
  • autoimmune diseases
Various normal functions of cell growth, metabolism, and division can fail or work in abnormal ways and lead to diseases.
Cytopathology is best used as one of three tools, the second and third being the physical exam and medical imaging. Cytology can be used to diagnose a condition and spare a patient from surgery to obtain a larger specimen. An example is thyroid FNA, many benign conditions can be diagnosed with a superficial biopsy and the patient can go back to normal activities right away. If a malignant condition is diagnosed, the patient may be able to start radiation/chemotherapy, or may need to have surgery to remove and/or stage the cancer.
Some tumors may be difficult to biopsy, such as sarcomas. Other rare tumors my be dangerous to biopsy, such as pheochromocytoma. In general, a fine needle aspiration can be done anywhere it is safe to put a needle, including liver, lung, kidney, and superficial masses.
Many clinicians are not trained to perform fine needle aspiration biopsies properly, and then when they do not obtain diagnostic material, believe that cytology is not useful. Proper technique takes time to master. Cytotechnologists and cytopathologists can assist clinicians by going to procedures and assisting with collection techniques. A "quick read" is a peek under the microscope and can tell the clinician if they have obtained enough diagnostic material. Cytological specimens also need to be properly prepared so that the cells are not damaged.
Sometimes more information about the specimen is helpful. Immunohistochemical stains and molecular testing can be performed, especially if the sample is prepared using liquid based cytology. Often "reflex" testing is performed, such as HPV testing on an abnormal pap test or flow cytometry on a lymphoma specimen.

Body regions

Cytopathologic techniques are used in the examination of virtually all body organs and tissues:

See also

References

  1. ^ Kirkpatrick et al. (1989). The Cassell Concise English Dictionary. London. pp. 324. ISBN 0-304-31806-X. 
  2. ^ Chapter 13, section of squamous cell carcinomas, in Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson. Robbins Basic Pathology. Philadelphia: Saunders. ISBN 1-4160-2973-7.  8th edition.
  3. ^ cytology at eMedicine Dictionary
  4. ^ Orell, S., et al. 2005. Fine Needle Aspiration Cytology. 4th Edition

External links

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