Monday, 5 March 2012
DIAGNOSIS OF CANCER (3rd Prof)
DIAGNOSIS OF CANCER
The diagnosis of cancer is an attempt to accurately identify the anatomical site of origin of the malignancy and the type of cells involved. Cancer can virtually arise in any organ or tissue in the body except fingernails, hair, and teeth.
The site refers to the location of the cancer within the body. The body part in which cancer first develops is known as the primary site. A cancer's primary site may determine how the tumor will behave; whether and where it may spread (metastasize) and what symptoms it is most likely to cause. The most common sites in which cancer develops include the skin, lungs, female breasts, prostate, colon and rectum.
Secondary site refers to the body part where metastasized cancer cells grow and form secondary tumors. A cancer is always described in terms of the primary site, even if it has spread to another part of the body. For instance, advanced breast cancer that has spread to the lymph nodes under the arm and to the bone and lungs is always considered breast cancer (and the spread to the lymph nodes, bones, and lungs describe the stage of the cancer).
There are many signs and symptoms that may indicate the presence of cancer. These may be observed directly, through imaging technologies, or confirmed by lab tests. However, these signs and symptoms of cancer may resemble those of other conditions. For example, weight loss and abdominal pain can be caused by stomach cancer or an ulcer. Pink or reddish urine can be caused by kidney cancer or a kidney infection. A biopsy (removal of tissue for microscopic evaluation) is preferred to establish, or rule out, a diagnosis of cancer.
A biopsy, together with advanced imaging technologies, may not only confirm the presence of cancer, but may also pinpoint the primary site and secondary site(s).
Cancer cells that do not look like their healthy counterparts are called undifferentiated, or, because they often look like very immature cells, primitive. The pathologist assigns a pathological grade to a tumor according to how aggressive the tissue looks under the microscope.
Cancers must be diagnosed by removing a sample of tissue from the patient and sending it to a pathologist for examination. This procedure is called a biopsy.
After the biopsy specimen is obtained, it is sent for examination to the pathologist, who prepares a written report with information designed to help the primary doctor manage the patient's condition properly.
TYPES OF BIOPSIES:
1. Excisional biopsy.
A whole organ or a whole lump is removed (excised). These are less common now, since the development of fine needle aspiration. Some types of tumors (such as lymphoma, a cancer of the lymphocytes) have to be examined whole to allow an accurate diagnosis, so enlarged lymph nodes are good candidates for excisional biopsies. Some surgeons prefer excisional biopsies of most breast tumors to ensure the greatest diagnostic accuracy, as they are very vascular organs and found to bleed excessively hence, whole organ is removed.
2. Incisional biopsy.
Only a portion of the lump is removed surgically. This type of biopsy is most commonly used for tumors of the soft tissues (muscle, fat, connective tissue) to distinguish benign conditions from malignant soft tissue tumors, called sarcomas. Local anesthesia is used for external tumors while general anesthesia is given for tumors which are present inside the chest or abdomen.
3. Endoscopic biopsy.
This is probably the most commonly performed type of biopsy. It is done through a fiberoptic endoscope inserted into the gastrointestinal tract (alimentary tract endoscopy), urinary bladder (cystoscopy), abdominal cavity (laparoscopy), joint cavity (arthroscopy), or trachea and bronchial system (laryngoscopy and bronchoscopy), either through a natural body orifice or a small surgical incision. The endoscopist can directly visualize an abnormal area on the lining of the organ and pinch off tiny bits of tissue with forceps attached to a long cable that runs inside the endoscope.
4. Fine needle aspiration (FNA) biopsy.
This is an extremely simple technique. A needle no wider than that typically used to give routine injections (22 to 25 gauge) is inserted into a lump (tumor), and cells are drawn up (aspirated) into a syringe. These are smeared on a slide, stained, and examined under a microscope by the pathologist. Tumors of deep, hard-to-get-to structures (pancreas, lung, and liver, for instance) are especially good candidates for FNA, and require no anesthesia, not even local anesthesia. Thyroid lumps are also excellent candidates for FNA. FNA is now widely applied in diagnosing breast lumps.
5. Punch biopsy.
This technique is typically used by dermatologists to sample skin rashes and small masses. After a local anesthetic is injected, a biopsy punch, which is basically a small (3 or 4 mm in diameter) version of a cutter, is used to cut out a cylindrical piece of skin. The hole is typically closed with a suture and heals with minimal scarring.
Laparoscopy is much like endoscopy but uses a slightly different scope (a laparascope) to look inside the abdomen and remove tissue samples. A small incision (cut) is made in the abdomen then the laparascope is passed through this opening to see inside. Procedures like this that look inside the chest are called thoracoscopy .
A laparotomy is a type of surgery that involves an incision into the abdomen, usually a vertical cut from upper to lower abdomen. This may be done when there is uncertainty about a suspicious area that cannot be diagnosed by less invasive tests (like a needle biopsy or laparoscopy). The doctor can look at the size of the area and where it is located. Nearby tissues can be checked, too. General anesthesia is used for this technique.
8. Bone marrow biopsy.
In cases of abnormal blood counts, such as unexplained anemia, high white cell count, and low platelet count, it is necessary to examine the cells of the bone marrow. In adults, the sample is usually taken from the pelvic bone.
With the patient lying on his/her stomach, the skin over the biopsy site is anesthetized with a local anesthetic. A larger rigid needle with a very sharp point is then introduced into the marrow space. A syringe is attached to the needle and suction is applied. The marrow cells are then drawn into the syringe. This suction step is occasionally uncomfortable, since it is impossible to deaden the inside of the bone. The contents of the syringe, which to the naked eye looks like blood with tiny chunks of fat floating around in it, is dropped onto a glass slide and smeared out. After staining, the cells are visible to the examining pathologist or hematologist.