Merkel cell carcinoma [Neuroendocrine carcinoma of the skin] is a rare and aggressive type of skin cancer, but it is becoming more common. It can grow quickly in its local area of the skin and can also spread to lymph nodes and other distant parts of the body such as the lungs, liver, bone or brain. Early diagnosis can be life-saving.
This skin cancer most commonly appears in the head, neck or face and most often develops in older people with a history of a lot of sun exposure. It is also more common in people with a compromised immune system. Merkel cell cancer can look like a sore or a shiny pink, red or purple spot. It can be difficult to spot a merkel cell cancer based on appearance alone.
Accurate and early diagnosis and treatment of Merkel cell cancer increases the probability of success. The process starts with a skin and lymph node exam and a skin biopsy. Once merkel cell cancer is confirmed, a sentinel lymph node biopsy [SLNBx link] is the best way to determine if the cancer has spread to nearby lymph nodes.
The Positron Emission Tomography scan, or PET scan, has been shown to be very useful for Merkel cell cancer. A PET scan uses radioactive tracers to detect disease in the body,- cancers of a large enough size (usually ~1 cm or larger) can have a bright signal on a PET body scan. Your doctor may also order other types of imaging, such as an ultrasound, CT scan or MRI.
Staging: Staging is a process to categorize the cancer by how big it has grown and how far it has spread
- Stage 1 The tumor is less than 2 cm in size and has not spread to lymph nodes or distant organs
- Stage 2 The tumor is greater than 2 cm in size but has not spread to lymph nodes or distant organs. It may involve muscle, bone, fascia or cartilage that is underlying the primary tumor
- Stage 3 The tumor spread to lymph nodes
- Stage 4 The tumor has spread to distant areas such as lung, liver, lymph nodes far away from the primary tumor or skin far away from the primary cancer
Treatment and Outcomes: Merkel cell cancer is usually treated with surgery [WLE link] to remove the cancer along with a wide rim of normal tissue around it. The wide rim or margin of normal tissue removed with the cancer decreases the chances of the cancer coming back. However, if the merkel cell cancer is on the face, a wide margin may not be possible or may be aesthetically unfavorable. Smaller margins or MOHS surgery [MOHS link] can be considered. If surgery is not possible or desirable, radiation can also be used as primary treatment – this decision should be discussed with the patient’s entire care team (medical oncologist, radiation oncologist, surgeon),.
If a sentinel lymph node biopsy shows that cancer has entered the lymph nodes, your doctor will most likely recommend removal of the lymph nodes in the neck. This may also include removal of a portion of the saliva gland called the parotid gland which contains lymph nodes overlying the face. After surgery, radiation is recommended to follow closely afterwards unless the cancer was very small. Radiation is used to treat the area of the cancer and possibly the area of the lymph nodes if the lymph nodes were involved. Chemotherapy can sometimes be used but has not been shown to demonstrate a clear benefit except when the merkel cell cancer has metastasized to distant organs.
If the cancer has spread to distant sites, a clinical trial is preferred. Surgery is usually not recommended and treatment with radiation and or chemotherapy or immunotherapy are the more common options at this point.
Surveillance and Survivorship: After the cancer is treated, merkel cell cancer has a higher risk of coming back in the same area than other skin cancers. It is recommended by the National Comprehensive Cancer Network, NCCN, to follow up with your physician regularly for physical check-ups every 3-6 months for the first two years and every 6-12 months thereafter. Most recurrences happen within the first two years.
Article by Alice Lin, MD