Skin cancer - Basal cell carcinoma, squamous cell carcinoma, and melanoma: Nursing

Skin cancer is the growth and proliferation of abnormal cells in the skin, and the most common types include basal cell carcinoma, squamous cell carcinoma, and melanoma.

Let’s start with the anatomy and physiology of the skin, which is divided into three main layers: the hypodermis, dermis, and the epidermis. The hypodermis is made of fat and connective tissue that anchors the skin to the underlying muscle and acts as a cushion that protects underlying tissues from trauma. Above the hypodermis is the dermis, containing hair follicles, nerve endings, as well as sweat glands, and blood vessels. And just above the dermis is the epidermis, which itself has multiple cell layers that are composed of developing cells called keratinocytes.

Now, keratinocytes start their life at the lowest layer of the epidermis, called the stratum basale or basal layer. As keratinocytes in the stratum basale mature, they migrate into the next layers of the epidermis, called the stratum spinosum, stratum granulosum, stratum lucidum, and finally, the stratum corneum, which is the uppermost and thickest epidermal layer. Now, the stratum basale also contains the melanocytes, which produce a pigment called melanin, that gives each individual their skin color. At the same time, melanin acts as a natural sunscreen, because its protein structure dissipates, or scatters UVB light.

So, the cause of skin cancer is mutations in skin cells, which can arise due to a variety of factors. The most important environmental risk factor is excessive UV radiation exposure, either from the sun or sunlamps and tanning booths. In general, light skinned clients are considered to be at a higher risk of developing skin cancer, and the risk increases with cumulative sun exposure over time. Other risk factors include exposure to occupational chemical carcinogens, like arsenic or coal tars; and the presence of premalignant skin lesions. These include actinic keratosis, which might develop into squamous cell carcinoma; and atypical or dysplastic nevi or moles, which can develop into melanoma

Some viral infections like human papillomavirus; and situations that cause immunosuppression like having HIV, or receiving prolonged treatment with glucocorticoids after organ transplantation, also increase the risk of skin cancer. Additionally, there are medications that increase skin sensitivity to UV radiation, like thiazide diuretics and tricyclic antidepressants. There are also genetic risk factors that include conditions like albinism and xeroderma pigmentosum, where clients are genetically predisposed to develop skin cancer even without the presence of environmental risk factors.

Now, let’s look at the pathology of skin cancer. A tumor develops if there’s a DNA mutation in any of the skin cell types that leads to uncontrolled cell division. Typically these are mutations in proto-oncogenes which result in a promotion of cell division, or mutations in tumor suppressor genes which result in a loss of inhibition of cell division. As the tumor keeps growing, new blood vessels also develop via angiogenesis to supply it. Some of these tumors stay well contained or localized. But some can start invading neighboring tissues, and may even spread to nearby lymph nodes or metastasize to distant organs, such as the brain, bones, or liver.

Now, skin cancer is classified based on the type of skin cell from which it arises. The most common type is basal cell carcinoma, or BCC for short, which arises from cells in the stratum basale. Basal cell carcinomas tend to be slow growing tumors that rarely metastasize, but can be locally invasive.

The second most common type of skin cancer is squamous cell carcinoma or SCC, which arises from squamous keratinocytes, above the stratum basale. There are three stages of squamous cell carcinoma. First, there’s actinic keratosis, which is a precancerous lesion where keratinocytes that are damaged by radiation begin to over-produce keratin. Next, there’s Bowen disease, which is also called squamous cell carcinoma in situ. At this point, the tumor can be found in the epidermis, but it has not broken through the basement membrane. Finally, invasive squamous cell carcinoma breaks through the basement membrane, can extend into the dermis, and may even reach the hypodermis. Squamous cell carcinoma rarely metastasizes, but it is more likely to do so than basal cell carcinoma.

Finally, the most aggressive form of skin cancer is melanoma, which derives from melanocytes and has a high risk of metastasis. Now, a melanocytic nevus, more commonly known as a mole, results from abnormal melanocytes that over-produce melanin. These moles can be considered precancerous because they carry an increased risk of turning into melanoma. Melanomas grow horizontally within the epidermis and superficial dermis; and also vertically, invading the dermis. Melanoma is considered the most aggressive type of skin cancer, because it metastasizes quickly.

Now, clinical manifestations are different for each type of skin cancer. The classic location of a basal cell carcinoma is the upper lip, but it can also develop on the face and trunk. Basal cell carcinoma typically appears as well circumscribed, erythematous, and slow growing papules. In clients with light skin, the lesions can have pearly borders and small, dilated blood vessels running over it, also known as telangiectasias. In clients with dark skin, lesions are usually more pigmented, and the pearly borders and telangiectasias are less obvious. In addition, these lesions can frequently develop central ulceration or crusting.

Next up is squamous cell carcinoma. In light skinned clients, it typically develops on sun-exposed skin areas such as the face, ears, and hands. In clients with dark skin, SCC often appears in areas that aren’t exposed to the sun.

Now, clinical appearance depends on its stage. So, actinic keratosis can appear as dry, rough, almost sandpaper-like patches that are surrounded by tan, brown, red, or flesh colored skin. Squamous cell carcinoma in situ usually appears as small, erythematous, scaly, and well circumscribed elevations of the skin. These lesions can be tender and bleed when touched. Finally, invasive squamous cell carcinoma can appear as a firm, red, and well circumscribed elevation of the skin. As the lesion grows, there can be pain or pruritus, and the center may become necrotic and can eventually turn into an ulcer. In late stages, excessive keratinization can lead to the formation of a scale or horn.

Finally, to clinically distinguish melanoma from a normal mole, remember the ABCDE mnemonic for melanoma appearance. A is for asymmetrically shaped lesions, B for irregular or notched borders, C is for different colors within the same lesion, D is for a diameter larger than 6mm, and e for a lesion that rapidly evolves over time, meaning a change to the size, color, shape or number of lesions. These lesions can be itchy or painful. In light skinned clients, melanoma usually develops on the back, chest or legs. In contrast, in clients with dark skin, melanomas might appear on the palms, soles, or mucous membranes, as well as under the nails.

Now, regardless of its type, skin cancer can cause other signs and symptoms when it invades deeper structures, like nerves, or the orbit of the eye. In the first case, clients can experience numbness, pain, and muscle weakness. When it invades the orbit, skin cancer can cause diplopia, which means seeing double; proptosis, or bulging of the eyeball; and ophthalmoplegia, or weakness of the eye muscles. Also, when there’s metastasis to lymph nodes, these might become enlarged, and there can be signs of distant metastases to the liver, like jaundice; the bones, like bone pain; and the brain, like headaches, confusion, seizures or poor coordination.