Dermatological Skin Conditions

Our skin is the largest organ of the body and is exposed to a variety of external and internal factors that can lead to different skin conditions. Below are some common dermatological skin conditions, their descriptions, and brief explanations of their causes.

Basal Cell Carcinoma / BCC

What is Basal Cell Carcinoma?

Basal cell carcinoma (BCC) is a prevalent type of skin cancer that arises from keratinocytes, often referred to as nonmelanoma skin cancer. It is the most common form of skin cancer and is sometimes called a rodent ulcer or basalioma. Individuals diagnosed with BCC frequently develop multiple primary tumors over the course of their lives.

Basal Cell Carcinoma - BCC
Basal Cell Carcinoma

What causes Basal Cell Carcinoma?

The development of BCC is influenced by multiple factors:

  • DNA mutations in the patched (PTCH) tumor suppressor gene, which is part of the hedgehog signaling pathway, are commonly involved.
  • These mutations are often triggered by prolonged exposure to ultraviolet (UV) radiation.
  • Both spontaneous genetic mutations and inherited gene defects can increase the risk of developing BCC.

Squamous Cell Carcinoma Dermoscopy / SCC

What is Squamous Cell Carcinoma?

Cutaneous squamous cell carcinoma (SCC) is a common form of nonmelanoma skin cancer that originates from keratinocytes. It typically appears on sun-exposed areas of the skin and can become invasive, with the potential to spread (metastasize). Often referred to simply as SCC, it poses a greater risk than other nonmelanoma skin cancers due to its ability to metastasize.

Squamous Cell Carcinoma Dermoscopy / SCC
Squamous Cell Carcinoma Dermoscopy
Squamous Cell Carcinoma

What causes Squamous Cell Carcinoma?

The causes of cutaneous squamous cell carcinoma (SCC) are linked to various factors, including:

  • Prolonged exposure to ultraviolet (UV) radiation, primarily from the sun, which damages the DNA in skin cells.
  • Tanning beds can also increase the risk of SCC due to artificial UV exposure.
  • Chronic skin inflammation or injury, such as from burns or scars, can contribute to the development of SCC.
  • Immunosuppression, whether from medications or medical conditions, weakens the body’s ability to repair skin cell damage.
  • Exposure to carcinogens, such as arsenic or radiation, may also increase the likelihood of developing SCC.
  • Genetic predisposition plays a role, with certain inherited conditions making some individuals more vulnerable to SCC.

Melanoma

What is Melanoma?

Melanoma, also known as malignant melanoma, is a potentially life-threatening form of skin cancer characterized by the uncontrolled growth of melanocytes, the pigment-producing cells in the skin. Normally, melanocytes are located in the basal layer of the epidermis, where they produce melanin, a pigment that protects skin cells by absorbing harmful ultraviolet (UV) radiation. While non-cancerous growths of melanocytes lead to moles (benign melanocytic nevi) and freckles (ephelides and lentigines), the malignant growth of these cells results in melanoma.

What causes Melanoma?

Melanoma is believed to originate from the uncontrolled growth of melanin-producing cells (melanocytic stem cells) that have undergone genetic changes. These mutations can be either acquired or inherited. Acquired or ‘sporadic’ mutations, which occur due to cell damage over a person’s lifetime, are the most common cause of melanoma. The primary culprit is overexposure to UV radiation from the sun or tanning beds.

Inherited (familial) melanoma, though far less common (under 10%), results from germline mutations passed down from parents. The CDKN2A gene (also known as p16INK4A or MTS1) is linked to 20-40% of familial melanomas. Other genes such as CDK4, MC1R, MITF, TERT, ACD, BAP1, POT1, and TERF2IP have also been implicated in recent years.

Cutaneous melanoma can develop on seemingly normal skin (in approximately 75% of cases) or from an existing mole or freckle that begins to grow larger and change in appearance.

Melanoma In Situ

What is Melanoma In Situ?

Melanoma in situ is the earliest stage of melanoma, where cancerous cells are confined to the epidermis, the outermost layer of the skin. Also referred to as in-situ melanoma or level 1 melanoma, it has not yet spread to deeper layers. Since melanoma in situ poses no immediate threat to life, early detection is crucial for improving survival rates. Identifying melanoma at this early stage reduces the risk of complications, lowers treatment costs, and leads to better outcomes compared to more advanced stages of the disease.

Melanoma In Situ
Melanoma In Situ
Melanoma In Situ on back
Melanoma In Situ upper back

What causes Melanoma In Situ?

Melanoma in situ is marked by genetic mutations in the DNA of melanocytes, primarily caused by exposure to ultraviolet (UV) radiation. These mutations trigger abnormal cell growth, leading to the early development of melanoma, although the cancerous cells remain confined to the epidermis at this stage.

Atypical Mole/ Dysplastic Naevus

What is Dysplastic Naevus?

The term “dysplastic nevus” specifically refers to a mole with distinct microscopic characteristics. However, only a small percentage of clinically atypical nevi meet the criteria for a dysplastic nevus upon microscopic examination. Many nevi that are histologically dysplastic may appear clinically normal, often being small, uniformly colored, and structurally consistent.

Dysplastic naevus
Dysplastic naevus

What causes Dysplastic Naevus?

The causes of dysplastic nevi are primarily related to genetic and environmental factors:

  • Genetic Factors: Individuals with a family history of dysplastic nevi or melanoma may have a higher risk due to inherited genetic mutations or susceptibility.
  • Sun Exposure: Excessive UV radiation from the sun or tanning beds can contribute to the development of dysplastic nevi by causing genetic mutations in skin cells.
  • Genetic Mutations: Specific genetic mutations and variations can lead to the development of dysplastic nevi. These mutations may affect the way skin cells grow and interact.
  • Familial Syndromes: Certain inherited conditions, such as familial atypical multiple mole melanoma (FAMMM) syndrome, can increase the likelihood of developing dysplastic nevi.

Seborrhoeic Keratosis

What is Seborrhoeic Keratosis?

Seborrheic keratosis is a benign, warty growth commonly seen in adults as a sign of skin aging. These lesions can vary in number, with some individuals developing hundreds over their lifetime. Also known as seborrheic keratosis (American spelling: seborrheic keratosis), it may be referred to as SK, basal cell papilloma, senile wart, brown wart, wisdom wart, or barnacle.

The broader term “benign keratosis” encompasses several related scaly skin lesions, including:

  • Seborrheic Keratosis: The primary condition, characterized by its warty appearance.
  • Solar Lentigo: Often difficult to distinguish from a flat seborrheic keratosis, it is a sun-induced spot.
  • Lichen Planus-Like Keratosis: A variant that can develop from an existing seborrheic keratosis or solar lentigo.

What causes Seborrhoeic Keratosis?

The exact cause of seborrheic keratoses is not well understood. Despite the name, these lesions are not confined to the seborrheic areas (such as the scalp, mid-face, chest, and upper back) associated with seborrheic dermatitis. They are not formed from sebaceous glands like sebaceous hyperplasia, nor are they related to sebum production, which is oily.

Seborrheic keratoses are considered degenerative in nature, meaning they tend to increase in number as individuals age. In some cases, a genetic predisposition can lead to the development of a large number of these lesions.

Actinic / Solar Keratosis

What is Actinic Keratosis?

Actinic keratosis is a precancerous, scaly spot that appears on skin damaged by sun exposure, also known as solar keratosis. It is considered an early form of cutaneous squamous cell carcinoma (a type of keratinocyte cancer) and may potentially develop into skin cancer if left untreated.

What causes Solar Keratosis?

Actinic keratoses develop due to abnormal skin cell changes resulting from DNA damage caused by short-wavelength UVB radiation. They are more likely to occur in individuals with compromised immune function, which can be due to aging, recent sun exposure, underlying health conditions, or the use of certain medications.

Intradermal Naevus

What is Intradermal Naevus?

An intradermal nevus is a type of mole or birthmark that occurs within the dermis, the layer of skin located below the epidermis. Unlike other types of nevi, which may be located in the epidermis or at the junction between the epidermis and dermis, intradermal nevi are characterized by their placement entirely within the dermal layer.

Intradermal nevi are commonly seen in adults and are often removed for cosmetic reasons or if there is any concern about changes in appearance.

What causes Intradermal Naevus?

The exact cause of intradermal nevi is not fully understood, but several factors are believed to contribute to their development:

  • Genetic Factors: A genetic predisposition can play a significant role, as some individuals may inherit a tendency to develop nevi.
  • Sun Exposure: Prolonged or intense exposure to ultraviolet (UV) radiation from the sun or tanning beds may contribute to the formation of nevi, although intradermal nevi are generally less directly associated with sun exposure compared to other types of nevi.
  • Hormonal Changes: Hormonal changes, such as those occurring during puberty or pregnancy, can influence the development of nevi.
  • Skin Trauma: Repeated trauma or irritation to the skin might contribute to the formation of intradermal nevi, though this is less common.
  • Aging: Intradermal nevi often develop in adulthood and may become more prominent with age due to changes in skin structure and pigmentation.

Overall, while these factors can influence the development of intradermal nevi, they are typically benign and not associated with cancer.

Dermatofibroma

What is Dermatofibroma?

A dermatofibroma is a common benign fibrous nodule typically found on the skin of the lower legs. It is also known as a cutaneous fibrous histiocytoma. These nodules are usually firm, raised, and can vary in color from brown to reddish. They are composed of fibrous tissue and are generally harmless, although they can be removed for cosmetic reasons or if they cause discomfort.

Dermatofibroma
Dermatofibroma

What causes Dermatofibroma?

The exact nature of dermatofibromas remains uncertain, with debate over whether they represent a reactive process or a true neoplasm. These lesions consist of proliferating fibroblasts, and histiocytes may also be involved. While dermatofibromas are sometimes linked to minor trauma, such as insect bites, injections, or injuries from rose thorns, this association is not consistent.

Additionally, multiple dermatofibromas can occur in individuals with altered immune systems, including those with HIV, immunosuppression, or autoimmune conditions.

Pilomatricoma

What is Pilomatricoma?

Pilomatricoma is an uncommon, benign tumor that originates from hair matrix cells, which are involved in hair follicle development. Also spelled “pilomatrixoma,” it is sometimes referred to as “calcifying epithelioma of Malherbe.” Though harmless, pilomatricomas can present as firm, raised lumps under the skin and are typically found on the face, neck, or upper body.

What causes Pilomatricoma?

The cause of pilomatricoma is attributed to a localized mutation in hair matrix cells. This mutation involves an overactive proto-oncogene called BCL-2, which indicates that the normal process of cell death is suppressed. In most cases, mutations in the CTNNB1 gene lead to the dysregulation of a protein complex known as beta-catenin/LEF-1, contributing to the formation of the tumor. These genetic changes disrupt normal cell processes, leading to the benign growth seen in pilomatricomas.

Lentigo Simplex

What is Lentigo Simplex?

Lentigo simplex is the most common form of lentigo, characterized by a single or multiple lesions (lentigines) that may appear at birth or, more commonly, in early childhood. Unlike other types of lentigines, lentigo simplex is not triggered by sun exposure and is not linked to any underlying medical conditions. It is also known as simple lentigo or juvenile lentigo. These spots are generally harmless and benign.

Lentigo simplex Head cheek central right
Lentigo simplex Head cheek central right1

What causes Lentigo Simplex?

The exact cause of lentigo simplex is unknown. When multiple lentigines appear without any associated medical conditions, the condition is termed lentigines profusa or generalized lentigines. However, when multiple lentigines are accompanied by other abnormalities, they become part of specific disease syndromes, such as:

  • Peutz-Jeghers syndrome
  • Xeroderma pigmentosum
  • LAMB syndrome
  • LEOPARD syndrome
  • Carney's complex

Each of these syndromes involves distinct clinical features beyond the presence of lentigines.

Junctional Naevus

What is Junctional Naevus?

A junctional nevus is a type of mole where the melanocytes (pigment-producing cells) are located at the junction between the epidermis (outer layer of skin) and the dermis (the layer just below). These nevi are usually flat or slightly raised and tend to be darker in color, ranging from brown to black.

Dysplastic naevus junctional and compound
Dysplastic naevus junctional and compound1

Key features of junctional nevi:

  • Appearance: Typically flat, smooth, and uniformly pigmented.
  • Location: Found at the junction of the epidermis and dermis.
  • Age: Commonly appear in childhood or adolescence.
  • Benign Nature: While generally harmless, junctional nevi can be monitored for changes, as alterations in size, shape, or color may warrant further evaluation for malignancy.

In some cases, junctional nevi can evolve into compound or intradermal nevi over time.

What causes Junctional Naevus?

The exact cause of a junctional nevus is not fully understood, but several factors may contribute to its development:

  • Genetic Predisposition: Genetic factors play a significant role in the formation of moles, including junctional nevi. Individuals with a family history of moles are more likely to develop them.
  • Sun Exposure: Ultraviolet (UV) radiation from the sun can stimulate melanocytes, potentially leading to the formation of new moles, including junctional nevi, or changes in existing ones.
  • Hormonal Changes: Hormonal fluctuations during periods like puberty, pregnancy, or hormonal treatments can trigger the appearance of junctional nevi.

These moles are typically benign, but changes in size, shape, or color should be monitored, as they can occasionally indicate a risk of malignancy.

Compound Naevus

What is Compound Naevus?

A compound nevus is a type of mole in which melanocytes (pigment-producing cells) are found in both the epidermis (the outer layer of skin) and the dermis (the deeper layer beneath the epidermis). This distinguishes it from other types of moles, such as junctional nevi (where melanocytes are confined to the epidermis) and intradermal nevi (where melanocytes are found only in the dermis).

compound naevus Leg thigh extensor side right
Dysplastic naevus Trunk upper back
Dysplastic naevus Trunk upper back1

Key features of a compound nevus:

  • Appearance: Usually raised and may have a slightly bumpy surface. It can be brown, black, or skin-colored, often darker in the center.
  • Location: Melanocytes are found in both the epidermal-dermal junction and within the dermis.
  • Common Age: Often appears in childhood or adolescence.
  • Benign: Compound nevi are generally harmless but should be observed for any changes in size, shape, or color, as these can sometimes indicate a risk of malignant transformation.

Compound nevi may evolve over time, with some eventually becoming intradermal nevi as melanocytes migrate deeper into the skin.

What causes Compound Naevus?

The exact causes of a compound nevus are not fully understood, but several factors are believed to contribute to its development:

  • Genetic Factors: A genetic predisposition can increase the likelihood of developing compound nevi. People with a family history of moles or nevi are more prone to developing them.
  • Sun Exposure: Ultraviolet (UV) radiation from the sun can trigger the development of compound nevi. Excessive sun exposure, particularly during childhood, can cause melanocytes to proliferate, forming these types of moles.
  • Hormonal Changes: Hormonal fluctuations, such as those occurring during puberty, pregnancy, or hormonal therapies, can stimulate the development of new moles, including compound nevi, or cause changes in existing ones.
  • Aging: Compound nevi typically develop in childhood or adolescence but can also appear later in life as part of the natural aging process.

While compound nevi are usually benign, changes in size, shape, or color may warrant further medical evaluation, as they could indicate an increased risk of melanoma.