What kind of mole may be melanoma? How to detect early metastasis? Nuclear medicine examination plays a key role

What kind of mole might be melanoma?

Many melanoma patients in China suffer from subungual melanoma , which initially appears as only a black line on the nail, which gradually widens, bulges, and ulcerates.

How to diagnose nail melanoma?

Melanoma can metastasize, but not all melanomas will metastasize. It usually grows "horizontally" or "radially" (grows sideways) in the early stages, and the tumor is confined to the epidermis. During this period, the damage expands irregularly in the horizontal direction. Since there are no blood vessels and lymphatic vessels in the epidermis, complete surgical resection can cure most patients at this time without metastasis. If left untreated, the tumor will then enter a "vertical" growth phase (i.e., grow vertically), and as the depth of tumor invasion increases, the risk of metastasis or even death will gradually increase.

How to detect early metastasis of melanoma?

There are many ways to determine whether a tumor has metastasized, such as determining whether there are enlarged lymph nodes through palpation, and assisting in the determination through imaging examinations, such as lymph node ultrasound, whole-body CT, bone scan, or PET/CT examination.

If no clear metastatic lesions are found in imaging examinations, but the tumor invasion has reached a certain depth, it is considered that there is a possibility of metastasis, and a special examination/surgery is required - sentinel lymph node imaging + biopsy .

Sentinel lymph nodes are like sentinels that can detect enemy situations in advance. If we find the first lymph node (sentinel lymph node) to which the tumor begins to metastasize, and remove the lymph node for pathological examination, we will know the truth about whether the tumor has metastasized. Sentinel lymph nodes are of great significance for the staging diagnosis of tumors and the formulation of subsequent treatment plans.

If the sentinel lymph node is positive, the entire lymph node area needs to be cleared. Sentinel lymph node imaging + biopsy is a combination of nuclear medicine examination and surgical methods. It requires the injection of technetium-labeled colloid tracers around the tumor, followed by lymph node imaging and tracing, and dynamic observation of the tracer flowing back along the lymph. When the tracer is observed to be concentrated in the lymph node, a SPECT/CT examination is performed to locate the specific location of the lymph node and mark it on the body surface. During a lymph node biopsy, the surgeon can use the probe of the gamma detector to detect the sentinel lymph node (the highest reading), remove it and send it to the pathology examination room.

It should be noted here that although this operation is a nuclear medicine examination, the dose of tracer injected into the sentinel lymph node is extremely small and the radiation dose is very low, basically equivalent to the amount of radiation received by the body after taking a few flights, so the patient and the medical staff performing the operation do not need special protection. However, since this operation requires the cooperation of the nuclear medicine department and special instruments, there are not many hospitals in China that can standardize sentinel lymph node biopsy for melanoma.

With the support of the first batch of new technologies and new projects, Peking Union Medical College Hospital, led by the Department of Dermatology and in collaboration with multidisciplinary MDTs such as nuclear medicine, orthopedics, basic surgery, breast surgery, and obstetrics and gynecology, has successfully carried out sentinel lymph node imaging and biopsy for many years, which has ensured a crucial link in the diagnosis and treatment of melanoma patients.

The MDT for Skin Malignancies/Melanoma of Peking Union Medical College Hospital was established in 2020. Led by the Department of Dermatology, it collaborates with 11 other disciplines in the hospital to provide multidisciplinary, standardized, and full-process management for melanoma patients.

How to treat melanoma?

The treatment of melanoma is not something that can be accomplished independently by a single discipline, and requires multi-disciplinary diagnosis and treatment (MDT). Early detection of melanoma and extended surgical resection can greatly improve the prognosis. Once lymph node metastasis occurs, melanoma does not respond very well to drugs and radiotherapy. Although there have been many new advances in drug treatment, such as targeted therapy and immunotherapy, most melanomas in China are acral, and the available drugs and the response rates of existing drugs are relatively limited. Fortunately, most melanomas grow on the skin, which is easy to observe. Therefore, everyone should always be vigilant and try to identify and actively treat melanoma as early as possible.

▌The popular science theme of this article comes from the theme of the 4th issue of "Journal of Peking Union Medical College" in 2023: Radionuclide diagnosis and treatment and clinical transformation

Editor: Liu Yang and Zhao Na

Proofreading: Li Na, Li Yule, Dong Zhe, Li Huiwen

Producer: Wu Wenming

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