If a person is suspected to have skin cancer due to signs and symptoms, 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 help in selecting an appropriate treatment option.
Following are some commonly used diagnostic tools for different types of skin cancers:
- Biopsy: Biopsy samples contain a small number of cells or a tiny piece of tissue collected from the affected area with the help of a special biopsy instrument. Biopsy sample(s) are generally collected when an abnormal area(s) is observed during the physical examination indicating skin cancer.
It is very important to obtain a biopsy sample because it can establish the diagnosis of skin cancer. It can also provide other useful information about the cancerous cells, such as the type of skin cancer, the severity of cancerous changes involved (grade of cancer), and the presence of specific defective genes.
Following are common techniques used for collecting the biopsy samples from the affected area/lymph nodes:
Shave Biopsy: In shave biopsy, a biopsy sample is obtained by shaving the upper layer of the skin using a surgical blade. This technique is generally employed for early-stage disease confined to the superficial skin layer.
Punch Biopsy: In this technique, a biopsy sample containing deeper skin tissues is obtained using a tool with a round blade that cuts through all the skin layers. This technique enables biopsy of skin cancers that have invaded into nearby tissues.
Surgical biopsy: In this technique, a tissue sample from the affected site is removed via a surgical procedure. When only a part of the tumor 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 skin cancer. The surgical biopsy technique may also be used to obtain a biopsy sample from an affected lymph node.
Sentinal Lymph Node Biopsy (SLNB): In this surgical biopsy procedure, the sentinal lymph node (the first lymph node affected by cancer) along with some nearby lymph nodes are removed and checked for the presence of cancer cells. An absence of cancer is the sentinel lymph node indicates cancer has not spread to other lymph nodes.
To find a sentinel lymph node, a surgeon first injects a radioactive substance and/or a dye into the cancer tissue. The sentinel lymph node is then determined as the first node detected to have radioactivity and/or the first lymph node that take-up the dye color. Detected sentinel lymph node is then removed and tested in a laboratory for the presence of cancer cells.
Fine Needle Aspiration (FNA) Biopsy: This technique is generally used to collect a biopsy sample from an enlarged lymph node near the skin via a fine hollow needle attached to a syringe. A very small sample is usually obtained with this technique that can be tested to establish the diagnosis of the skin cancer in the suspected lymph node(s). This technique is most commonly used and very easy to perform with minimum side effects. It can also be utilized to diagnose disease progression or recurrence in patients who have received treatment.
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- 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 within the primary tissue affected and in the nearby tissue can also be assessed with the help of these techniques. These are primarily employed after the establishment of the pathological diagnosis to estimate the extent of disease. Also, they can be employed after treatment to evaluate the treatment efficacy and to detect any signs of disease progression/recurrence.
Computed tomography (CT) scan: In this technique, detailed cross-sectional images of internal structures are generated using x-rays with or without intravenous/oral contrast (like barium). This technique can accurately detect the tumor’s size, location, invasion to nearby structures (for example, the bones), and spread of disease to nearby lymph nodes or to distant body parts (for example, the lungs and the liver).
This is very helpful for planning the treatment in case radiation therapy is indicated for the treatment. It can sometimes be used to guide a biopsy needle to collect biopsy samples from the affected area/lymph node.
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, spinal cord, etc.
This technique is better than CT for the examination of soft tissues in the limbs, but inferior to CT for examining the bones. Additionally, it can be used for planning radiation treatment.
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. It is usually combined with CT scan (PET/CT) to accurately diagnose the spread of disease in distant body parts.
Bone Scan: In this test, a radioactive material is injected into the vein of the patient, which gets accumulated in the areas of bones affected by the disease, which are then detected with the help of radioactivity detectors. In this way, it may help to detect the spread of cancer to bones.
Certain blood tests may also be employed in the patients with skin cancer 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.