By Dr Ananya Mandal, MD
There are several methods of diagnosing cancer. With advances in technologies that understand cancers better, there is a rise of number of diagnostic tools that can help detect cancers. Once suspected, diagnosis is usually made by pathologists and oncopathologists and imaging radiologists.
Some types of cancer, particularly lymphomas, can be hard to classify, even for an expert. Most cancers need a second opinion regarding diagnosis before being sure of the diagnosis or stage and type.
The most common diagnostic methods include:
This is a test where a small sample of tissue is taken from the suspected cancer with the help of a fine tipped needle (fine needle aspiration – FNA), or with a thicker hollow needle (core biopsy) or by surgical excision. The tissues are then examined under a microscope for the presence of cancer cells. Depending on tumor location, some biopsies can be done on an outpatient basis with only local anesthesia.
Sentinel node biopsy
This is a procedure where the closest and most important nodes near the cancer are surgically excised and examined. Since sentinel nodes are the first location that cancer is likely to spread, only these lymph nodes that likely contain cancer cells.
In this imaging technique a thin, flexible tube with a tiny camera on the end is inserted into the body cavities. This allows the doctors to view the suspicious area. There are many types of scopes, each designed to view particular areas of the body. For example, a colonoscope looks at the colon and large intestine and a laparoscope is used to look within the abdomen etc.
Blood tests can be performed to detect the normal blood cells as well as for specific tumor markers. Some tumors release substances called tumor markers, which can be detected in the blood. A blood test for prostate cancer determines the amount of prostate specific antigen (PSA). Higher than normal PSA levels can indicate cancer. Similarly in ovarian cancer a tumor marker CA-125 is released.
Bone marrow aspiration
These show a picture of the bone marrow that may be affected in leukemias and blood cancers.
Pap test (Pap smear) is a routine test where a sample of cells from a woman’s cervix is examined under the microscope. This helps identify changes in the cells that could indicate cervical cancer or other conditions.
Sputum analysis and bronchial washing analysis
The cells of the sputum and bronchial secretions are analyzed under the microscope for signs of lung and other respiratory cancers.
There are several imaging techniques. These include X rays, CT scans, MRI scans of various parts of the body.
X-rays are the most common imaging techniques and they may be made more specific by using a Barious enema. This is used for detection of stomach and small intestinal growths and cancers.
Mammogram is an X-ray of the breasts used to screen for and/or detect breast lumps and growths.
A CAT scan (computerized axial tomography) uses radiographic beams to create detailed computerized pictures. It is more precise than a standard X-ray.
An Magnetic Resonance Imaging (MRI) uses a powerful magnetic field to create detailed computer images of the body’s soft tissue, large blood vessels and major organs. Both CT scan and MRI can also be used with contrast radio-labelled dyes to obtain a more clear and specific picture of the cancer.
An Ultrasound uses high-frequency sound waves to determine if a suspicious lump is solid or fluid. These sound waves are transmitted into the body and converted into a computerized image.
Bone scan is specifically used to identify and locate new areas of cancer spread to the bone. Normally a Positron imaging test (PET scan) is used. A Gallium scan is another nuclear medicine test in which a special camera takes pictures of tissues of the body after a special radioactive tracer is injected into a vein. The cancerous areas light up under the scanner.
Cytogenetic analysis involves analysis of blood or bone marrow cells for organizations of chromosomes. This shows up any genetic mutations.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)