Skin is the outer covering of the body and is the largest organ in the body. The skin is formed of layers. The outer layer is called the Epidermis and the inner layer is called the Dermis. Underneath the dermis is tissue called the subcutaneous tissue that contains fat, blood vessels etc. Underneath that are muscles and other structures and organs.
A cancer that arises from the skin is called as Skin cancer. There are instances where cancers starting in other parts of the body spread to the skin. This is called as secondary skin cancer. In this section we will be talking at Primary skin cancer- that has started in the skin.
There are different types of Skin Cancer and the common ones are given below.
- Basal Cell Carcinoma
- Squamous Cell Carcinoma
- Malignant Melanoma
- Other uncommon skin cancers include a Lymphoma on the skin, Merkel cell Carcinoma
Skin cancer is more common in the caucasian population. It is not very common in India. The following are potential risk factors for the development of Skin cancer.
Significant exposure to the sun or UV rays is a risk factor for skin cancer. This exposure is usually over many years prior to developing the cancer.
Exposure to radiation or radiotherapy in the past is a risk factor for getting Skin cancer. This exposure can be from treatment for other cancers or conditions with radiation.
Suppression of the body’s immune system due to disease or due to medications (after organ transplant) can be a risk factor for the development of Skin cancer.
The presence of chronic ulcers on the skin for long periods can be a risk factor for the development of Skin cancer.
Exposure to chemicals such as Arsenic increase the risk.
The following symptoms can be present in a patient with Skin cancer.
Lump or Lesion on the Skin
A Basal cell Carcinoma (BCC) or a Squamous cell Carcinoma(SCC) appear as lumps or ulcers on the skin. A BCC can be a dark, brown or black lump present in the sun exposed part of the body such as head, face or neck. These areas can develop a scar on top of them, can bleed or attempt to heal but do not heal completely. They can be itchy or scaly. An SCC can be like an ulcer, be red in colour and can also bleed sometimes.
A Melanoma is usually dark in colour. Patient may notice a pervious mole changing in size suddenly, changed colour, become itchy, bleeding or having an irregular edge. A mole may develop satellite lumps that were not present before.
Enlargement of Lymph nodes
Occasionally, patients may noticee enlarged lymph nodes in the area which could be a symptom that is first recognised.
Other symptoms such as weight loss, tiredness, loss of appetite, swelling of abdomen, cough and breathlessness are seen in advanced disease particularly with Melanoma.
Visual Inspection and Examination
Skin cancer can be suspected and diagnosed by examination using a dermoscope if needed.
A biopsy of the suspected lesion is essential to make a diagnosis of Skin cancer. The biopsy can be of various types.
A punch biopsy takes a small sample of growth that is seen on the skin.
An Excision biopsy involves removal of the abnormal area with a margin of normal skin. This type of biopsy may serve the purpose of diagnosis and treatment of the condition.
It is important to note that there are many skin conditions that look like cancers but are not. If there is a suspicion of such a condition, it is best to see a Skin specialist for further tests which may include a biopsy.
If advanced Skin cancer is suspected as in a Melanoma or Squamous cell Carcinoma, scans such as CT scan or a PET-CT scan may be requested to look for spread of cancer to other parts of the body. Such scans are only done in some situations.
Genetic and Molecular Testing
In Melanoma, particularly advanced or metastatic melanoma, genetic testing on the biopsy sample is done to look for mutations. Treatment strategies are different depending on the presence of specific mutations in the cancer.
Treatment of Skin Cancer can be divided into Non-Melanoma and Melanoma as the options are different. This section talks about treatment of Non-Melanoma Skin Cancer.
Removal of the skin cancer with surgery is a common option of treatment. When this option is chosen, the cancer along with a margin of normal skin is removed. Surgery may not always be the best option of treatment and this depends on the location of the cancer, the fitness of the patient or patient chooses another option. In some situations, a skin graft or other type of reconstruction is needed after removing the diseased area to fill the defect in the skin. Surgery is done with local anaesthesia for small cancers. A special type of surgery called Moh’s micrographic surgery is done sometimes to ensure clear margins. In treatment of some SCC’s, the surgeon may remove surrounding lymph nodes at the same time to look for spread of cancer into those lymph nodes.
Radiotherapy, like surgery is another curative option of skin cancer such as BCC or SCC. Radiotherapy is frequently used when surgery is not possible due to closeness of the cancer to sensitive areas or if the patient chooses this option instead of an operation or is not well enough for an operation. Both Surgery and Radiotherapy have an equal chance of curing the condition. When Radiotherapy is used, it is given daily, five days a week for 4-6 weeks. Side effects are mild and resolve over a few weeks. Radiotherapy for skin cancer is different to other cancers as low energy radiotherapy or electrons are used here which have less penetration than standard radiotherapy. This leads to side effects mainly on the skin only. Side effects of such radiotherapy include redness of the skin, soreness of the skin. The cancer on the skin can turn into an ulcer which heals and scars over a period of 6 weeks to 3 months and then heals completely.
Cryotherapy is use of freezing temperatures to freeze and kill off cancer cells. A cryotherapy probe is placed on the cancerous area and the area is frozen. This type of treatment is used for small cancers on the skin. The tissue freezes and dies off. It darkens and falls off after some time leaving a scar behind.
In the rare instances where there is advanced Skin cancer that has spread to different parts of the body and is not curable, Chemotherapy is used with the aim to control the cancer and improve symptoms. For small skin cancers, chemotherapy in the form of ointment or cream can be tried.
Early stage Melanoma
Treatment of early stage Melanoma consists of surgical removal of the Cancer. This is called a wide excision where the Cancer along with a wide margin of normal skin around the Cancer is removed.
In Melanomas that arise in the arms, legs or chest and abdomen, surgical removal of the regional lymph nodes is considered. This is particularly so in Melanomas which have a medium and high risk of recurrence.
The lymph node removal is with the help of sentinel node sampling.
Sentinel node Sampling
Sentinel node is first node or nodes that the cancer can spread to. If there is no cancer in the sentinel node, then the chance of there being cancer in other axillary nodes is small.
A sentinel node is usually found around the Cancer after injection of a small dose of radioactive substance or a blue dye into the area close to the Cancer. This dye is taken up by the first lymph node/s that the dye spreads to. These substances help the surgeon to locate the nodes at surgery.
These removed nodes are then examined under the microscope for cancer cells. If there are no cancer cells, there is no further need for surgery. However, if cancer cells are found, then the surgeon may decide to remove all other lymph nodes nearby.
Adjuvant therapy is use of other treatment options after definitive curative treatment is done to increase the chances of cure of a Cancer. In melanoma, adjuvant treatment with Immunotherapy (Nivolumab) is given for patients with stage 3 onwards after surgery. For Melanoma that is stage 1 and 2, there is no need for adjuvant treatment and surgery alone is sufficient.
Treatment of Advanced Melanoma
Advanced or stage 4 melanoma is one that has spread to different parts of the body from its primary starting point. The treatment options aim to control the disease and achieve long term control.
Immunotherapy and Biological Therapy
All patients with metastatic melanoma are tested for the presence of mutations in the Cancer for BRAF, MEK and KIT. For patients without the presence of such mutations in their Cancer are treated with Immunotherapy drugs such as Nivolumab and Pembrolizumab. These drugs can be given alone or in combination with Ipilimumab which is an antibody against CTLA-4. If mutations are presents in the above-mentioned sites, drugs such as Vemurafenib, Dabrafenib and Trametinib are used to treat it. This is usually after treatment with Immunotherapy.
The benefit of chemotherapy in advanced melanoma is very small and not used often.
Surgery is not normally an option of treatment in metastatic melanoma but is used in some settings where disease is limited to one area of the body.