Procedures and Tests
Reviewed by: HU Medical Review Board | Last reviewed: May 2017. | Last updated: February 2022
Your doctor spotted a suspicious lesion during a physical exam. The next step is testing to determine if it is cancer. Skin biopsy can provide a definitive diagnosis of cancer. Additional procedures check whether the cancer has spread.
A skin biopsy is when your doctor removes a sample of skin tissue. A pathologist studies the sample under a microscope. By looking at the abnormal cells, the pathologist can diagnose skin cancer with certainty.
Information from the biopsy helps to determine the cancer stage. The skin biopsy provides information about the cancer such as:1
- Tumor thickness
- How quickly cancer cells are dividing (mitotic rate)
- Whether the top layer of cell has broken down (ulceration)
- Whether the cancer cells are found on the edge of the sample (positive margins)
- Whether the tumor has invaded a nerve, blood vessel, or lymph vessel
- Whether tiny tumors are present near the main tumor (microsatellitosis)
- Whether immune cells have invaded the tumor
The biopsy procedure may remove some or all of the suspected tumor. Procedures that remove all of the lesion are called “excisional biopsy.” Procedures that remove a section of the lesion are called “incisional biopsy.” Your doctor will choose the procedure based on the lesion size, location, and the suspected type of skin cancer.2,3 Doctors prefer excisional biopsy for suspected melanoma.3
Lymph node biopsy
To see whether skin cancer has spread beyond the skin tumor, a sample of tissue can be taken from nearby lymph nodes. Melanoma that invades deep layers of skin may reach the lymph vessels and spread via the lymph, a fluid that contains white blood cells.4,5 The lymph node closest to the tumor is the most likely place to find cancer that has spread. Not everyone with melanoma needs a lymph node biopsy. Lymph node biopsy is used for people with signs of or risk factors for metastasis.
Swollen, hard, and enlarged lymph nodes indicate that cancer may have reached the lymph nodes.6 Samples from enlarged lymph nodes are taken in two ways:
- Fine needle aspiration: tissue is removed using a thin needle.
- Surgical lymph node biopsy: the lymph nodes are surgically removed.
If you have a thicker (>1 millimeter) melanoma and no lymph node symptoms, your doctor might recommend sentinel lymph node biopsy.7 Sentinel lymph node biopsy is done to find microscopic cancer cells in a lymph node.4 Microscopic cancer is too small to feel or see with imaging tests.
Sentinel node biopsy was studied in a high-quality trial. This trial had more than 2000 patients with melanoma.8 Researchers compared survival in people who did and did not have sentinel node biopsy. Biopsy lead to higher 10-year disease-free survival rates.8 People with mid-thickness tumors (1.20 to 3.50 millimeters) and lymph node metastasis had better outcomes if they had a biopsy.8 Biopsy identified the metastasis early. Early treatment reduced the chance that the cancer returned in the lymph nodes or spread to distant organs. It also reduced the risk of death from melanoma.
Imaging tests help to find melanoma that has spread. This information contributes to cancer staging and deciding on the best course of treatment. Imaging is mainly used for people with late stage melanoma (III or IV) or symptoms of cancer metastasis.9 These tests are rarely used in early-stage melanoma.
Imaging tests create a picture of the inside of your body. Computed tomography (CT) uses x-rays to produce 3-dimensional images of organs, bones, and other tissues.10 CT imaging can be used with positron emission tomography (PET).6,11 A PET scan measures body function. These functions include blood flow, oxygen use, and sugar (glucose) uptake by cells.11 Cancer cells are more active than most normal tissue. They stand out on a PET scan. Your doctor uses functional information from the PET scan with detailed CT images to figure out if the cancer has spread.
The lungs and brain are common locations for melanoma metastases.12 Chest x-ray may be done to look for melanoma that has spread to the lungs.6 Magnetic resonance imaging (MRI) may be done to look for brain metastases. MRI uses a strong magnet and radiowaves to produce a picture.13 MRI does not expose you to radiation.
Blood test: Lactate dehydrogenase
A blood test for lactate dehydrogenase (LDH) is done for people with distant metastatic (Stage IV) cancer. LDH is an enzyme found in the blood. High LDH is a sign of cancer that is harder to treat.6
Emerging non-invasive technology
Invasive tests are tests that disturb the body. For example, blood draws and biopsy are invasive tests. Non-invasive tests do not break the skin or physically enter the body. Non-invasive tests currently used in skin cancer include dermatoscopy—when a special microscope is used to look at a lesion—and imaging tests.
It may not be possible to biopsy all suspicious lesions. New non-invasive tests may help identify lesions that need further testing. “Optical biopsy” is a way to study a lesion without taking tissue.6 Reflectance confocal microscopy (RCM) is one kind of optical biopsy. RCM sends laser light into the skin as far as the dermis. The light is reflected back to form a picture.14,15 This technology is mainly used in research right now.14
Handheld scanners send multiple wavelengths of energy into the skin to create pictures of a lesion.14 Use of these devices is controversial. It is unclear whether they are any better than an experienced dermatologist at finding melanoma.14
Smartphone apps have been developed that claim to identify melanoma.14 Some of these apps use algorithms to analyze photos. Other apps send images to remote dermatologists who evaluate the lesion. Safety and accuracy are important considerations for individuals planning to use these apps. Given their limitations, apps cannot replace a total body skin exam for finding suspicious lesions.