Common Pathology Tests
The most common test in anatomical pathology is the biopsy, which involves removing cells or tissue from the body in order to examine it for the presence of disease. A biopsy may be performed with or without anesthesia, depending on the location of the tissue or cells to be extracted. Several types of biopsies exist, and cross various disciplines of medicine.
- Breast: Breast biopsies are usually performed to investigate a lump identified during breast examination or a lesion identified on mammography. The main objective of the pathologist is to determine if there is cancer or if the tissue sample is benign. If cancer is identified, then an attempt is made to classify the cancer into the specific type and severity (grade) of the cancer. Some benign lesions confer a higher risk of malignancy, which may prompt the clinician to perform a repeat biopsy or take a larger sample.
- Dermatology: Skin biopsies are often performed to examine tissue for the presence or absence of cancer cells. If a tissue is found to be cancerous, the determination can then be made if the cells are benign or malignant. Each specimen is marked with a special ink around the edges to define the margins of the sample. If cancer cells are present and they extend up to or into the margin area, this will alert the physician that some cancer cells may have been left behind and a larger excision of tissue in the affected area is needed. Skin biopsies can also be used to determine if a rash is due to allergies, infection, or skin diseases such as psoriasis.
- Gastrointestinal: This biopsy involves removing tissue or cells from the lining of the GI Tract. Common reasons a GI biopsy is done are to look for signs of inflammatory disease such as Crohn’s disease or ulcerative colitis, examine the composition of intestinal polyps, and assess for the presence of cancer cells.
- Liver/Hepatology: A biopsy of the liver is most commonly performed when a patient has signs of abnormal liver function, such as jaundice or abnormal blood tests. The common conditions that liver pathologists look for include infections such as Hepatitis B and Hepatitis C, and alcohol related liver damage such as cirrhosis. Occasionally a biopsy is also performed to investigate a tumor, which may be benign or malignant. Liver biopsies are frequently performed on patients who have undergone a liver transplant, to make sure the transplanted liver is healthy and functioning well.
- Neurology/Brain: Biopsy of the brain is an uncommon procedure and is usually performed when a patient has abnormal findings on a CT scan or MRI scan of the brain identified during the course of investigations for symptoms such as severe headaches or seizures. When a brain biopsy is performed, the neurosurgeon frequently asks the pathologist to perform a ‘frozen section’ diagnosis, which is a rapid but imperfect assessment of the tumor while the patient is still under anesthesia, and is intended to help the surgeon decide if sufficient tissue has been obtained. The ‘final diagnosis’ is usually rendered a few days later, at which time the original frozen section diagnosis is refined to yield a more precise report.
- OB-GYN: A uterine biopsy involves removing cells and tissue from the lining of the uterus to examine the composition of growths such as fibroids or polyps or look for signs of infection or cancer. Likewise, a biopsy of the cervix is performed if dysplasia or cancer is suspected and a biopsy may be taken of an ovary mass to determine the presence of cancer. Biopsy during pregnancy is also common; chorionic villus sampling (CVS)—removal of placenta tissue from the uterine cavity - is performed early in a pregnancy to assess the fetus for genetic defects. CVS, like certain other biopsy testing, is done under the guidance of ultrasound to determine proper positioning of the needle used to remove the tissue.
- Urology: Biopsies are commonly conducted to examine the prostate gland in men or the bladder in both men and women. Conditions such as cancer, infection, cysts, and ulcers can be detected with bladder biopsy. The prostate biopsy is done mainly to examine prostate tissue for signs of cancer after an abnormal blood test or a lump is detected during a physical examination.
The National Institutes of Health provides a comprehensive listing of common biopsy techniques and how each is preformed.
Two common molecular pathology tests, in situ hybridization (ISH) and polymerase chain reaction (PCR), aim to identify chromosomal abnormalities and mutations of our genetic code, or DNA.
ISH is a genetic test conducted to determine the presence or absence of specific DNA sequences. It is commonly used in reading of Pap tests or to determine if certain sexually transmitted diseases are present, as well as myriad other uses.
PCR involves amplifying a segment of DNA so that thousands, even millions of identical copies of that segment are made to enables pathologists to examine specific genes to look for abnormalities or even to compare genes from person to person or family to family, which can be helpful in identifying if a disease is genetic (passed down family lines) or has randomly presented in a particular individual. This information can be helpful in various ways, such as determining treatment or in genetic counseling to couples planning a family.
An example of such as test would be PCR testing to determine if a woman is a carrier of the cystic fibrosis gene. If she is not, she will not pass on the disease to any child to who she gives birth. However, if she does carry the gene for cystic fibrosis, she can ask her mate to undergo testing as well. If both male and female are carriers, they may wish to undergo other pathological testing (such as pre-implantation genetic diagnosis (PGD) or genetic counseling prior to starting a family.
PCR is also serves as a foundation for a broad base of diagnostic tests related to infectious diseases. This test can detect and quantify various pathogens, such as HIV, Hepatitis B and C, and Human Papillomavirus (HPV).