Skin cancer is a disease that occurs when skin cells undergo abnormal and uncontrolled growth, typically due to DNA damage from ultraviolet (UV) radiation exposure, either from the sun or artificial sources like tanning beds. There are three main types: basal cell carcinoma (the most common and least aggressive), squamous cell carcinoma (more aggressive but still highly treatable), and melanoma (the most dangerous form that spreads very quickly in form of metastasis).

The disease usually develops on sun-exposed areas of skin and can appear as new growths or changes in existing moles, with warning signs including changes in color, size, or shape of skin lesions, along with symptoms like bleeding, itching, or pain.

How common is skin cancer?

In the United States and Europe, skin cancer accounts for approximately 15-20% of all malignant diseases, and this number has been steadily increasing in recent years.

Skin cancer predominantly affects older adults and occurs equally among men and women. High-risk groups include fair-skinned individuals (Fitzpatrick phototypes I and II) and those exposed to elevated levels of ultraviolet (UV) radiation, such as residents of sunny regions or high-altitude areas.

Where it develops?

Skin cancer can develop anywhere on the body where there are skin cells, but it tends to appear in specific locations depending on several key factors.

Most commonly, skin cancer develops in areas that receive frequent sun exposure. Think of your skin like a map where the “high-traffic” areas for sunlight are most vulnerable. The face is particularly susceptible, especially the nose, cheeks, and forehead, as these areas typically receive the most direct sunlight throughout our lives. The ears, neck, chest, and backs of hands are also common sites, as they often go unprotected from UV radiation during daily activities.

However, skin cancer can be sneaky – it can also develop in places that rarely see the sun. Melanoma, the most dangerous type, can appear in surprising locations like between the toes, under fingernails or toenails, on the palms of hands, soles of feet, and even in the eyes. For people with darker skin tones, these hidden areas are actually where melanomas most often develop, particularly on the palms and soles.

Think of it like this: while sun exposure is like repeatedly striking a match in the same spot (making those areas more likely to “catch fire” in the form of cancer), sometimes the fire can start in unexpected places due to genetic factors, previous injuries, or other causes we don’t fully understand.

Mechanism of development

Under normal conditions, skin cells continually regenerate. However, under the influence of UV radiation, genetic predispositions, or random cellular errors, mutations may occur. This disrupts the natural lifecycle of skin cells, leading to uncontrolled division and the potential formation of a malignant tumor.

If cancerous cells enter the bloodstream or lymphatic system, they can spread to other parts of the body, forming new disease sites known as metastases.

Causes of skin cancer

No single cause leads to skin cancer. Normal cells in the human body become malignant due to genetic alterations, with UV radiation being the primary trigger for skin cancer.

The skin acts as a protective barrier against pathogens, chemicals, and physical factors, making it highly susceptible to damage. Natural repair mechanisms within the skin help to restore these damages. If DNA damage occurs, the body’s defenses attempt to repair it. If repair isn’t possible, the body initiates programmed cell death, or apoptosis, to prevent further harm.

Genetic factors

In some cases, mutations occur in genes responsible for repairing or eliminating defective cells, known as tumor suppressor genes. For example:

• p53 Gene: Plays a key role in initiating apoptosis. Mutations in this gene often serve as the starting point for skin cancer development.
• Fas Ligand (FasL): Normally ensures that cells do not transform into tumors and facilitates the destruction of defective cells. Chronic UV exposure can decrease the activity of this gene, impairing its protective functions.

Basal cell carcinoma is often associated with mutations in the Sonic Hedgehog (SHH) signaling pathway, which is essential for proper cellular growth and replication.

Oncogenes and their role

In addition to tumor suppressor genes, oncogenes also play a significant role. Mutations in these genes lead to increased activity, resulting in uncontrolled cell proliferation. For example, mutations in the BRAF oncogene are frequently found in melanoma cells, contributing to their aggressive growth and spread.

This complex interplay of genetic mutations, environmental exposure, and cellular repair mechanisms highlights the multifactorial nature of skin cancer development and the importance of prevention and early detection.

Types of skin cancer

Based on the type of cells from which the tumor originates, researchers classify skin cancer into two main categories: melanoma and non-melanoma tumors.

Melanoma

Melanoma (from the Greek melanos—”black”) is a malignant tumor that develops from skin cells that produce the pigment melanin, known in medicine as melanocytes.

Most melanomas form on the skin, but they can also develop in the retina of the eye, mucous membranes of the mouth, rectum, and the membranes of the brain and spinal cord.

The main factor contributing to melanoma is overexposure to ultraviolet (UV) radiation.

Risk Factors for Melanoma:

• Fair skin prone to sunburns (Fitzpatrick skin types I and II).
• A large number of dysplastic nevi (moles) on the body.
• Hereditary predisposition—cases of melanoma in close relatives.
• History of sunburns.

A high number of dysplastic moles significantly increases the risk of melanoma.

Several types of melanoma are recognized in medicine. The most common types include superficial spreading melanoma, nodular melanoma, acral melanoma, amelanotic melanoma, and lentigo melanoma.

Superficial spreading melanoma

This is the most common type, accounting for up to 70% of cases.

It typically develops from a dysplastic nevus but can also arise on unaffected skin. Early-stage tumors appear as irregularly shaped brown spots with well-defined edges, slightly elevated above the skin surface. The coloration is usually uneven, with visible black or gray-pink patches, and a reddish border may appear at the edges.

As the tumor progresses, the spot darkens, becomes denser, shiny, and uneven. Nodules may form, and the surface may bleed or develop crusts.

Nodular melanoma

This is the second most common type, accounting for 15–30% of cases.

It typically forms on unaltered skin (without moles) and is often found on areas most exposed to sunlight, such as the head, neck, and legs in women. Less frequently, it occurs on the torso.

Nodular melanoma appears as a dark blue, dark brown, or black nodule with a central ulcer.

This type does not spread along the skin’s surface but grows inward, rapidly affecting the subcutaneous tissue and metastasizing to lymph nodes.

Lentigo melanoma

This type accounts for 5–10% of diagnosed melanomas.

It usually develops on exposed body parts, such as the face, ears, neck, scalp, and the backs of the hands.

Lentigo melanoma evolves over years or decades from malignant lentigo, resembling a freckle or flat pigmented spot with a yellowish, pink, or brownish hue. As the tumor grows, its coloration becomes more uneven, its edges blur, and papules (small nodules) or a single nodule may appear on its surface. The surface may crack and bleed.

Acral melanoma (subungual)

This tumor primarily affects individuals of Asian and African descent. It typically forms on the nail bed, palms, and soles.

Acral melanoma is unique in that its development is triggered not by UV radiation but by skin injuries, burns, frostbite, or exposure to harsh chemicals (acids, alkalis).

It appears as dark brown or black stripes, sometimes extending to the nail fold or finger skin. Over time, the nail cracks, exposing dark, bleeding tissue underneath.

Amelanotic (non-pigmented) melanoma

This is a rare type of melanoma that is challenging to diagnose due to its atypical appearance. It manifests as a small, pale pink or reddish-blue, dense nodule with a rough texture. As it deteriorates, an ulcer with firm, raised edges forms. It can occur anywhere on the body but is more common on the fingers and soles.

Basalioma

Basalioma is a tumor that forms from the cells of the basal layer of the skin. These cells are located in the deepest layer of the skin and constantly divide. Under normal conditions, they move from the lower layer to the skin’s surface, where they keratinize and gradually exfoliate.

Externally, basalioma typically appears as a small red nodule that may occasionally bleed and develop a crust. Due to its seemingly “insignificant” appearance, many people mistakenly regard it as an ordinary wound or “sore.”

Basalioma often resembles a harmless wound that, in the opinion of most people, “should heal on its own over time.”

The exact causes of the tumor’s development are not yet established, but there are factors that significantly increase the risk of basal cell carcinoma.

Risk factors for basalioma development:

• Prolonged exposure to ultraviolet radiation — both sunlight and artificial light from tanning beds.
• Fair skin — Fitzpatrick skin types I and II.
• Weakened immune system.
• Age — the older a person is, the higher the likelihood of developing basalioma.
• Exposure to carcinogenic substances — such as arsenic and petroleum products.
• Genetic predisposition — cases of basalioma among relatives.

Medicine distinguishes several clinical forms of basaliomas, depending on the tumor’s external appearance.

Solid or nodular-ulcerative basalioma

This form most often develops on the face and neck, less frequently on the body. The tumor appears as a small shiny nodule or a larger transparent or pinkish node with a pearly sheen, sometimes showing visible vascular stars on the surface.

The center of the node is often covered with a thin, loosely attached scaly crust, under which erosion is found. The edge of the lesion may be thickened. If untreated, the tumor can penetrate deep into the tissues, affecting subcutaneous fat and muscles, even with minimal skin ulceration.

Ulcerative basal cell carcinoma

Resembles a light pink or reddish nodule that gradually increases in size. The surface becomes lobular, with vascular stars appearing. Ulcers form in the center, covered with crusts, and surrounded by a dense, raised rim with small nodular thickenings resembling pearls.

Superficial basalioma

This type is more common in younger people. Red or pink patches with clear boundaries and fine, flaky scaling appear on the skin (typically on the torso, arms, or legs). The tumor grows very slowly, often over many years.

Pigmented basalioma

A rare form characterized by a high concentration of melanocytes — pigment-producing skin cells. It often manifests as dark, pigmented areas within the lesion, visually resembling melanoma. This type is more commonly found in people with Fitzpatrick skin types III and IV.

Sclerodermiform basalioma

A rarer but more aggressive form of basal cell carcinoma. It primarily occurs on the skin of the head and neck and appears as dense plaques of flesh-colored or light red with a yellowish tint, featuring blurred edges. It visually resembles scar tissue, with active growth zones sometimes identified around the lesion’s periphery.

Sclerodermiform basaliomas rarely bleed or ulcerate (this typically happens in later stages) but may develop alongside the nodular form of basal cell carcinoma.

Fibroepithelial form (pinkus fibroepithelioma)

A very rare and unusual form of basalioma, most commonly found on the lower back. It looks like a dense pink nodule on a stalk and rarely ulcerates.

Squamous cell skin cancer

Squamous cell skin cancer (squamous cell carcinoma) is a malignant tumor that develops from keratinocytes (the main cells of the skin) and also from hair follicle cells.

This type of cancer can occur on any part of the body but is most commonly found on the skin of the head, face, legs, and hands.

The exact causes of squamous cell skin cancer are not yet definitively established. However, several factors are known to increase the likelihood of developing this disease.

Risk factors for developing squamous cell skin cancer:

• Prolonged exposure to ultraviolet radiation — both sunlight and artificial light from tanning beds.
• Fair skin — Fitzpatrick skin types I and II.
• Weakened immune system.
• Age — the older the person, the higher the likelihood of developing squamous cell skin cancer.
• Exposure to carcinogenic substances — such as arsenic and petroleum products.
• Genetic predisposition — cases of squamous cell skin cancer among relatives.
• Chronic skin conditions.
• Infection with human papillomavirus (HPV) types 16, 18, 31, 33, 35, and 45.
• Albinism — a congenital lack of melanin pigment in the hair, skin, and eyes.

The main clinical types of squamous cell skin cancer are exophytic (tumorous) and endophytic (ulcerative) forms.

The exophytic form of squamous cell carcinoma typically appears as a nodule or plaque tightly adhered to adjacent tissues. The tumor protrudes above the skin and is covered with crusts or keratinous scales. Sometimes growths resembling cauliflower form on its surface.

If the tumor is not diagnosed and treated in time, the exophytic form can transform into the endophytic form.

The endophytic form grows rapidly into surrounding tissues and destroys them. Externally, it appears as a crater-like ulcer with an uneven base covered in a yellowish coating, which bleeds easily and may develop a crust.

Stages of skin cancer

The development of non-melanoma skin cancer is classified into five stages, each of which characterizes the size of the tumor, its spread to neighboring tissues, and the presence of metastases.

Stages of non-melanoma skin cancer development:

• Stage 0: The pathological process is confined to the upper layer of the skin. There are no tumor cells in the nearby lymph nodes or other organs.
• Stage I: The tumor is no larger than 2 cm in diameter, with no metastases. There is one high-risk factor.
• Stage II: The tumor is larger than 2 cm in diameter, and metastases (distant tumor foci) are present. There are two high-risk factors.
• Stage III: Cancer cells have spread to the adjacent bone tissue, but no metastases are present, or metastases are found in the nearest lymph node, but its size does not exceed 3 cm. The number of risk factors may vary.
• Stage IV:
  1. Cancer cells have spread to bone structures (ribs, spine).
  2. The affected lymph node exceeds 3 cm in diameter.
  3. Multiple lymph nodes are affected.
  4. Distant metastases are present in other organs.

High-risk factors:

• Tumor thickness exceeding 5 cm.
• Tumor has spread into subcutaneous tissue and beyond.
• Nerve fibers are involved in the tumor process.
• The tumor is located on the face (lip, ear).
• The tumor consists of poorly differentiated cells (they differ significantly from healthy cells and divide very rapidly).

For more precise staging of the disease, doctors use the TNM classification, which defines three main characteristics of the tumor:

• T (Latin tumor — “tumor”): extent of the primary tumor.
• N (Latin nodus — “node”): involvement of nearby lymph nodes.
• M (Latin metastasis — “spread”): presence of distant metastases.

Primary tumor — T:

• Tx: Insufficient data to assess the size of the primary tumor.
• T0: No primary tumor is detected.
• Tis (in situ): The tumor has not invaded neighboring tissues.
• T1, T2, T3, T4: Different sizes of the tumor.

For T1–T4 stages, additional letter designations are used:

• a: Tumor without ulceration.
• b: Tumor with ulceration.

Involvement of nearby lymph nodes — N:

• Nx: Metastases in nearby lymph nodes cannot be assessed.
• N0: No signs of lymph node involvement.
• N1: Metastases are detected in one lymph node.
• N2: Metastases are detected in 2–3 lymph nodes.
• N3: Metastases are detected in 4 or more lymph nodes, or there is a conglomerate (fusion) of adjacent and distant metastases.

Additional designations for N1–N2:

• N1/N2a: Metastases are detected microscopically.
• N1/N2b: Metastases are detected macroscopically (clinically).
• N2c: Distant metastases are present (no nearby tumor foci are found).

Distant metastases — M:

• M0: No distant metastases.
• M1: Distant metastases are present.

Letter designations for M:

• M1a: Metastases in the skin, subcutaneous fat, or non-regional lymph nodes. Lactate dehydrogenase (LDH) levels are normal.
• M1b: Metastases in the lungs. LDH levels are normal.
• M1c: Metastases in other organs or tumor foci at any location with elevated LDH levels in the blood.

Example diagnosis formulation:

T2aN0M0 — Stage II skin cancer without ulceration. Nearby lymph nodes are not involved in the malignant process, and there are no distant metastases.

Symptoms of skin cancer

In the early stages, skin cancer is often mistaken for other skin conditions or ignored altogether. As a result, many individuals seek medical attention only after the malignant growth has spread to surrounding tissues and formed multiple metastases.

Non-specific symptoms on early stages

• A skin growth that rapidly changes in shape, size, or color.
• Peeling, itching, cracking, or bleeding of the growth.
• Redness or swelling around the skin lesion.

Special attention should be given to moles with irregular shapes and uneven coloration (featuring spots of black, brown, pink, red, white, or blue) that grow rapidly.

If these symptoms appear, it is essential to consult a dermatologist.

Symptoms of melanoma

One of the earliest signs of melanoma is the enlargement of a mole (nevus). Its edges become blurred and asymmetrical. The mole’s color may change, and lighter patches sometimes appear in its center.

If the condition is not detected and treated promptly, melanoma progresses. The tumor becomes denser and darker (sometimes black) with a shiny surface. An ulcer may form at its center. Over time, regional lymph nodes enlarge, and the individual may experience symptoms such as reduced appetite, unexplained fatigue, and weight loss.

Symptoms of basal cell carcinoma (basalioma)

Initially, a small pale pink or flesh-colored nodule appears on the skin, which slowly increases in size. Gradually, a grayish crust forms in the center of the nodule, surrounded by a dense ridge made up of small nodular thickenings of a light gray color.

As the disease progresses, new nodules form and merge with each other. A network of spider veins may develop on the surface of this conglomerate, and a non-healing, bleeding ulcer often appears at its center.

The tumor becomes denser over time and, without treatment, may invade surrounding tissues, including bone structures, causing severe pain.

Symptoms of squamous cell carcinoma

Squamous cell carcinoma of the skin may present as a dense red patch that bleeds even with minimal contact and later forms a crust. This carcinoma may also resemble a nodule with a depressed center or an open, non-healing ulcer. In the keratinizing form, the lesion is covered with dense, horny scales.

Diagnosis

Self-diagnosis

Self-diagnosis is one of the key methods for detecting skin cancer at an early stage, allowing treatment to begin as soon as possible.

It is recommended to perform self-diagnosis up to 10 times a year, especially during the summer when the sun is most active, as well as in early autumn.

During self-diagnosis, carefully examine all areas of your body, including the skin under the hair. A small comb will be helpful for this purpose. Gently part your hair strands to inspect the skin underneath.

ACCORD system

• A — Asymmetry (uneven edges of a mole).
• K — Edge (blurred contour, serrations, irregularities).
• K — Bleeding (drops of blood on the surface of the lesion, crusts, burning sensation).
• O — Color (spots of black, dark brown, light pink, or other shades).
• R — Size (a lesion larger than 6 mm in diameter).
• D — Dynamics (the lesion is growing rapidly).

If such symptoms appear, consult a dermatologist.

Dermatoscopy

The doctor will inquire about when the lesion appeared on the patient’s skin and how quickly it is growing. The dermatologist will then examine the lesion using a dermatoscope — a special device consisting of a magnifying lens, a transparent plate, and a light source. This tool helps preliminarily determine the nature of the lesion, whether it is benign or malignant.

Hystology and biopsy

If the examination results suggest possible skin cancer, the doctor will order a histological analysis. This test identifies malignant changes in the tissues.

In addition, if skin cancer is suspected, the doctor may recommend testing for LDH (lactate dehydrogenase). This intracellular enzyme responds to pathological changes and is found in the blood when tissue cells are destroyed.

To assess the extent of the disease, the doctor may also refer the patient for a complete blood count, biochemical blood analysis, urinalysis, and ultrasound or biopsy of the regional (nearest) lymph nodes.

Treatment of skin cancer

The treatment strategy depends on the type of skin cancer, the extent of the disease, the location of the tumor, as well as the patient’s age and overall health.

Surgical treatment

One of the primary methods of treating skin cancer is the surgical removal of the tumor.

Doctors excise not only the tumor itself but also the surrounding tissues (within a radius of about 5 mm). This approach minimizes the risk of recurrence.

If studies show that lymph nodes are involved in the malignant process, they are also removed.

Main Methods of Tumor Removal:

1. Classical Excision with a Scalpel
   • The tumor is removed along with surrounding healthy tissue, the wound is sutured, and tumor samples are sent to a laboratory.
   • If there are aesthetic defects, simultaneous reconstructive surgery is performed.
2. Laser Removal
   • A special compound is applied to the tumor surface, followed by laser treatment.
   • Gradually, the tumor tissues begin to die off. The procedure is relatively lengthy (up to 40 minutes) but painless.
3. Mohs Micrographic Surgery
   • The tumor is removed layer by layer without affecting healthy tissues.
   • Each layer is sent to the laboratory for examination.
4. Curettage and Electrocautery
   • Tumor tissues are scraped off with a curette, and the wound is then cauterized with an electrocautery device.
   • After healing, the scar is barely noticeable. This method is mainly used for superficial basal cell carcinoma.
5. Cryodestruction
   • Tissues are treated with liquid nitrogen, causing them to gradually die off.

Chemotherapy

Chemotherapy may be prescribed as a standalone treatment or in combination with surgery.

The main goal of chemotherapy is to destroy cancer cells or at least reduce the pathological lesion. This method is effectively used when metastases are present.

Radiation therapy

Radiation therapy can be used alongside surgery or as an alternative when surgery is contraindicated or ineffective. The basis of radiation therapy is the use of ionizing radiation to target cancer cells.

Medication-based treatment

Medications are usually prescribed for inoperable skin cancer or if the tumor has metastasized:

• For squamous cell carcinoma and melanoma, drugs that stimulate the immune system are commonly prescribed.
• For basal cell carcinoma, vismodegib is used to prevent tumor cells from uncontrolled growth and division.

Additionally, for squamous cell carcinoma, the doctor may prescribe cytostatic drugs, which destroy all rapidly dividing cells in the body, primarily malignant ones.

Prognosis

The prognosis depends on the type of skin cancer, its stage, and the extent of tumor spread.

• Basal Cell Carcinoma (Basalioma):
  The prognosis is relatively favorable. The tumor grows very slowly, so it is often detected at an early stage, allowing timely treatment.
• Squamous Cell Carcinoma:
  The prognosis depends on the tumor’s size.
  • For small tumors (up to 2 cm in diameter), the five-year survival rate can reach 90%.
  • For larger tumors (2 cm or more), the survival rate drops significantly, nearly halving to 50%.
• Melanoma:
  The prognosis is directly influenced by the tumor’s stage:
  • Stage 1: Five-year survival rate is up to 90%.
  • Stage 2: Survival rate is 80–87%.
  • Stage 3: Survival rate ranges from 15–50%, depending on the number of affected lymph nodes.
  • Stage 4: Survival rate is approximately 5%.

How to prevent skin cancer

The primary rule for preventing skin cancer is protecting yourself from ultraviolet (UV) radiation.

Recommendations:

1. Minimize outdoor activities when the sun is at its peak.
2. Use products with high SPF and reapply every two hours.
3. Avoid artificial tanning in solariums.

Regularly inspecting the skin for new growths is crucial—this can be done through self-examination or by using the nevus mapping method.

• Nevus Mapping:
  This involves photographing and computer-analyzing all moles on the body. The technique allows monitoring the size and growth of neoplasms, helping to detect malignant processes at the earliest stage.

The procedure is entirely painless and lasts about one hour. It is recommended to undergo this examination at least once a year.

When is skin cancer fatal?

Skin cancer becomes fatal primarily when it metastasizes (spreads) to other parts of the body. While basal and squamous cell carcinomas rarely become fatal due to their slow growth and tendency to remain local, melanoma can be lethal if it reaches stage III or IV, when it spreads to lymph nodes and vital organs like the lungs, liver, or brain.

Without treatment, even non-melanoma skin cancers can eventually become life-threatening by growing deeply into tissues or, rarely, metastasizing. The key factor in preventing death is early detection – when caught in early stages, skin cancer has survival rates over 95%.

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