If a person is suspected to have STS, some investigations are required to confirm the diagnosis of the disease. Further, these investigations can help in determining the stage of disease, which in turn helps in selecting an appropriate treatment option.
Following are some commonly used diagnostic tools for STSs:
- Imaging Tests: These tests help in scanning a larger body area to assess the exact size and location of the disease and the spread of disease to distant body parts. The extent of invasion in the nearby tissue can also be assessed with the help of these techniques. Also, these tests are employed after treatment to evaluate the treatment efficacy and to detect any signs of disease progression/recurrence.
Ultrasound: In ultrasound, a transducer is used which directs very high-frequency sound waves towards the tissue to be examined. The sound waves are reflected off the internal structures depending on their ability to reflect these waves. The reflected sound waves are collected by a special detector (fixed near the transducer) to produce a real-time image of the internal tissues on a computer screen. This helps the doctor to examine the deeper tissues for any abnormality. This test can distinguish between fluid-filled cysts (usually benign) and solid tumor masses. The ultrasound test does not use any ionizing radiation and is considered as safe.
Computed tomography (CT) scan: In this technique, detailed cross-sectional images of body organs are generated using x-rays with or without intravenous/oral contrast. This technique can accurately detect the tumor’s size, location, invasion to nearby structures (for example, the bones), and spread to distant body parts (for example, the lungs and the liver). Sometimes, it can distinguish between a benign and a cancerous change and can even reveal the type of tissue involved (and thus the type of STS). This is very helpful for planning the treatment in case radiation therapy is indicated for the treatment. It can also be used to guide a biopsy needle to collect biopsy samples from the affected area.
Magnetic resonance imaging (MRI) scan: This technique provides detailed images of soft tissues in the body using radio waves, strong magnetic field, and gadolinium – the contrast material, which is used via intravenous injection to improve the clarity of the MRI images. Similar to CT, it can accurately diagnose the size, location, extent of invasion, and spread of disease to distant body parts, especially soft tissues like the muscles, eyeballs, blood vessels, brain, and spinal cord. Sometimes, it can distinguish between a benign and a cancerous change and can even reveal the type of tissue involved (and thus the type of STS).
It is better than CT for the examination of soft tissues in the limbs, but inferior to CT for examining the bones. Additionally, similar to CT, it can be used in planning radiation treatment for STSs. It can also be used to guide a biopsy needle to collect biopsy samples from the affected area.
Positron emission tomography (PET) scan: This technique uses a radioactive substance (known as fluorodeoxyglucose or FDG) that is given via intravenous injection prior to the procedure. Cancer cells absorb larger amounts of the radioactive substance than normal cells. The areas of higher radioactivity indicate cancerous tissue on the PET scan. This technique can be combined with CT scan (PET/CT) to accurately diagnose the extent of disease in distant body parts.
Bone Scan: In this test, a radioactive material is first injected into the vein of the patient. The radioactive substance gets accumulated in the areas of bones affected by the disease and such areas are then detected with the help of radioactivity detectors.
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- Biopsy: Biopsy samples contain a tiny piece of tissue collected from the affected area with the help of a biopsy instrument. Biopsy sample(s) are generally collected with the imaging study in case an abnormal area(s) is observed during the procedure or during the physical examination indicating STS.
It can establish the diagnosis of STS, the type of STS, the severity of cancerous changes involved (grade of cancer), and the presence of specific defective genes. The detected defect(s) can be targeted with the help of an appropriate treatment approach. Following are common techniques used for collecting the biopsy samples from the affected area/lymph nodes:
Core Needle Biopsy: In this technique, a hollow needle attached to a syringe is used to collect the biopsy sample from the affected area/lymph node.
A small sample of tissue is usually obtained with this technique that can be tested to establish the diagnosis of the STS. A fine needle aspiration can be utilized to diagnose disease progression or recurrence in patients who have received treatment.
Surgical biopsy: In this technique, a tissue sample from the affected site is removed surgically. When only a part of the affected tissue is removed, the procedure is known as the incisional biopsy. While in the case of excisional biopsy, the whole tumor is removed surgically. The magnitude of the procedure depends upon the location and the size of the tumor.
Excisional biopsy is usually performed when the tumor is located at an accessible site and do not involve any critical structure. It usually combines both diagnosis and treatment for the STS.
- Endoscopy: Endoscopy is a diagnostic technique which uses an endoscope – a long, flexible, slender tube usually equipped with a camera, a light source, and some special instruments for biopsy or surgery. A variant of the endoscopy, like the colonoscopy, double balloon endoscopy, or bronchoscope may be utilized depending upon the specific site involved.
These techniques enable to examine the lining of the specific structures and to determine the presence of any cancerous changes. The biopsy samples can also be collected with the help of special instruments if an abnormal area is observed during the procedure.
Certain blood tests may also be employed in the STS patients for the estimation of overall health, nutritional status, liver and kidney functions, and blood cells counts. These tests help in assessing whether the standard treatment like surgery, chemotherapy, or radiotherapy can be safely employed for the patient.