Merkel cell carcinoma (MCC) is a rare but aggressive form of skin cancer that originates in the outer layer of the skin. It is named after Merkel cells, which are specialised cells located close to nerve endings that play a role in the sense of touch.
While it was once thought to develop directly from Merkel cells, researchers now believe it forms from other types of cells that mutate and begin to look and behave like Merkel cells.
MCC is classified as a type of neuroendocrine tumour. Although neuroendocrine cells in the body receive signals from the nervous system and release hormones, this characteristic does not typically affect the prognosis or treatment for Merkel cell carcinoma patients. The disease is known to grow and spread, or metastasise, quickly, but it is sensitive to treatments such as radiation and immunotherapy.
MCC is a very uncommon cancer, affecting fewer than 1 in 100,000 people each year, with many people diagnosed annually in India. Despite its rarity, it is the second leading cause of skin cancer-related death, after melanoma.
The expected outcome, or prognosis, depends significantly on the stage at which the disease is caught:
75%
Five-year survival rate if the disease is caught before it has spread.
64%
Five-year survival rate if the cancer has spread to the lymph nodes.
24%
Five-year survival rate if the cancer has spread to distant sites in the body.
Factors that increase the risk of developing Merkel cell carcinoma include:
The risk increases with age, and it is rarely diagnosed in people younger than 50.
Men are more likely to develop MCC than women.
Up to 80% of Merkel cell carcinoma cases in India are linked to this virus. It is common and typically cleared easily by the body with no symptoms, but in a small number of people, it may contribute to MCC development.
Damage to the skin from natural sunlight or tanning beds is a primary risk factor for skin cancers.
Patients with compromised immunity have an increased risk. Causes include immunosuppressive medications, HIV infection, and cancers affecting immune cell production.
A history of previous cancer increases the risk of MCC.
It is important to bring any new or changing spots on your skin that persist for two weeks or more to your doctor's attention.
The main symptoms of Merkel cell carcinoma typically include:
This lump is often painless, firm, and red or violet in colour. It commonly appears in areas with significant sun exposure, such as the head, neck, arms, and legs. In some instances, the lump may break open and bleed.
Swollen lymph nodes near the cancer site can be a symptom, often indicating a more advanced stage of the disease.
Important: These symptoms do not automatically confirm a cancer diagnosis, but it is crucial to discuss any concerning changes with your doctor to rule out other health problems.
If you have persistent skin changes, your doctor will perform a physical examination of the suspicious area. If cancer is suspected, further tests will be conducted to establish a clear diagnosis.
Due to the rarity of Merkel cell carcinoma, diagnosis may require a specialist in skin conditions, known as an experienced dermatopathologist. SSCHRC has a team of expert dermatologists and dermatopathologists highly experienced in identifying MCC and its subtypes.
The following tests are commonly used to diagnose Merkel cell carcinoma and to monitor the patient's response to treatment:
A biopsy is the only definitive way to diagnose MCC. It involves removing a small tissue sample to be examined under a microscope for cancer cells. Depending on the tumour's location, a biopsy may be performed as an outpatient procedure under local anaesthesia, or a surgical biopsy may be required under general anaesthesia.
The different types of biopsy procedures include:
Imaging exams are typically performed after diagnosis to look for cancer inside the body. They help determine the cancer's stage by locating tumours and can track how the body is responding to therapy.
Imaging exams used for Merkel cell carcinoma include:
These tests are used to help monitor the disease and the patient's response to treatment.
Staging is the process of determining the tumour size and whether the cancer has spread. This information is critical for planning treatment and determining the prognosis.
Abnormal Merkel cells are found only in the top layer of the skin. These abnormal cells may become cancer and spread.
The tumour is 2 centimetres or smaller.
The tumour is larger than 2 centimetres.
The tumour has spread to nearby connective tissue, muscle, cartilage, or bone.
The tumour may be any size, with or without spread to nearby tissue. Cancer is found in a lymph node, either via sentinel lymph node biopsy (if a swollen node wasn't felt/seen) OR a swollen lymph node was felt/seen but the original cancer site is unknown.
The tumour may be any size and has spread to nearby connective tissue, muscle, cartilage, or bone, AND cancer is found in a swollen lymph node that was felt/seen. OR cancer is in a lymph vessel between the primary tumour and lymph nodes.
The tumour has spread to skin not close to the primary tumour, or to distant parts of the body such as the liver, lung, bone, or brain.
As a leading cancer centre, SSCHRC treats numerous Merkel cell carcinoma patients annually. This provides our multidisciplinary team of surgeons, medical oncologists, radiation oncologists, and dermatologists with extensive experience in managing the disease.
Treatment plans are tailored to the stage and extent of the cancer:
Surgery is a primary treatment for most early-stage MCC patients.
Radiation therapy uses powerful, focused beams of energy to destroy cancer cells. Due to the high effectiveness of radiation therapy against MCC, it is included in most treatment plans. In select cases, it may be the sole therapy recommended.
This type of treatment, a form of immunotherapy, works by preventing the body's immune system from deactivating itself prematurely, allowing it to continue fighting the cancer until it is eliminated. Patients may receive a single immunotherapy drug or a combination of multiple drugs.
Chemotherapy drugs work to kill cancer cells, control their growth, or relieve disease-related symptoms. Merkel cell carcinoma is known to be very sensitive to chemotherapy, which may be administered as a single drug or a combination of two or more, depending on the cancer type and its growth rate.