Skin Cancer

Jonathan Dunne

Skin Cancer

Skin cancer is the most common form of cancer worldwide, and it primarily develops as a result of prolonged exposure to ultraviolet (UV) radiation from the sun or tanning beds. The three most common types of skin cancer are basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma.

Basal cell carcinoma

The most frequently diagnosed form of any cancer. It arises from the basal cells, which are found at the bottom of the outer layer of the skin (the epidermis). BCC may appear as a small, pearly or flesh-coloured bump that may bleed, scab, or develop a central depression. It most often occurs on areas of the skin that receive frequent sun exposure including the face. The majority are managed by surgical excision and may require reconstruction of the area following removal. Although BCC rarely spreads (metastasises) to other parts of the body, it can grow locally and damage surrounding tissues if left untreated.

Squamous cell carcinoma

The second most common type of skin cancer. SCC is commonly found on sun-exposed areas and can present as a firm and crusted nodule or a flat red lesion that often ulcerated. It may be aggressive and can spread to lymph nodes or other organs if not treated early. Surgical removal is the mainstay of treatment and the wound may require reconstruction following removal.

Melanoma

It is less common than BCC or SCC, but it is a dangerous form of skin cancer due to its potential to spread (metastasise). Melanoma originates in melanocytes, the pigment-producing cells of the skin and may begin as a new mole or a change in an existing mole. Warning signs of melanoma can be remembered using the ABCDE rule: Asymmetry, Border irregularity, Colour variation, Diameter larger than 6 mm, and Evolving (changing) shape or colour.

Melanoma can develop on any part of the body, including areas not commonly exposed to the sun, and early detection is critical for effective treatment. Surgical removal is the mainstay of management and may include sentinel lymph node biopsy. Oncology treatments including targeted therapies and immunotherapy have changed treatment dramatically in recent years, leading to significantly improved outcomes.

In addition to the common forms of skin cancer—basal cell carcinoma, squamous cell carcinoma, and melanoma—there are several rare types of skin cancer. Though less frequently diagnosed, these cancers can be serious and often require specialised treatment. Below is a brief overview of the most notable rare types.

Merkel cell carcinoma

An uncommon but highly aggressive form of skin cancer that originates in Merkel cells, which are found in the skin’s upper layers and are associated with nerve endings involved in the sense of touch. This cancer often appears as a fast-growing, painless, firm nodule on sun-exposed areas such as the face, neck, or arms. Despite its small size, Merkel cell carcinoma has a high risk of spreading to other parts of the body and requires prompt treatment, which may include surgical excision, sentinel lymph node biopsy, radiotherapy and sometimes immunotherapy.

Sebaceous carcinoma

A rare and aggressive cancer that originates in the sebaceous (oil) glands of the skin, most commonly on the eyelids. It may be mistaken as a benign inflammation in the early stages (chalazion). Because it can spread (metastasise), early surgical removal and reconstruction is crucial.

Porocarcinoma

A rare and aggressive type of skin cancer that arises from the eccrine sweat glands, which are responsible for regulating body temperature through perspiration. It typically affects older adults and often presents as a solitary, slow-growing nodule, which may be flesh-coloured, red or ulcerated. while it may grow slowly at first, it has a capacity for local invasion and metastasis (spread). Early diagnosis, wide surgical excision, and close follow-up are key to managing this uncommon malignancy effectively.

Hidradenocarcinoma

A rare and aggressive skin cancer that arises from the sweat glands, specifically apocrine glands of the skin. Most often diagnosed in middle-aged to older adults, hidradenocarcinoma can occur on any part of the body, but it is commonly found on the head, neck, and trunk, areas which are rich in sweat glands. It typically presents as a slow-growing, firm nodule or mass that may be skin-coloured, red or blue in appearance. It does have high rates of local recurrence and metastasis (spread). The primary treatment for hidradenocarcinoma is wide surgical excision with clear margins, to reduce the risk of recurrence.

Microcystic adnexal carcinoma (MAC)

A rare, slow-growing but locally aggressive skin cancer that originates from sweat glands.. It typically appears as a firm, flesh-coloured or yellowish nodule or plaque, most commonly on the central face. Although MAC grows slowly and rarely spreads to distant organs, it may have deeper local invasion. Treatment typically involves surgical excision.

Atypical Fibroxanthoma (AFX) and Pleomorphic Dermal Sarcoma (PDS)

They are rare skin tumours that originate from the connective tissue cells in the dermis. They share many common features and are often considered part of a disease spectrum. However, they differ in behaviour and prognosis. Atypical fibroxanthoma is a rare, low-grade skin cancer that typically arises on sun-damaged skin, most often in older adults. Management is surgical excision, and it has a low risk of recurrence or metastasis.

Pleomorphic dermal sarcoma is closely related to AFX but is considered a more aggressive tumour. Like AFX, it often appears on sun-exposed skin in older individuals and presents as a firm, sometimes ulcerated or bleeding mass. However, PDS is distinguished by its tendency to invade tissues such as nerves, vessels and fat. Because of its greater potential for recurrence and, in some cases metastasis (spread), PDS is considered a higher-grade sarcoma. It requires a wide surgical excision and may necessitate radiotherapy treatment with ongoing surveillance.

Dermatofibrosarcoma protuberans (DFSP)

A rare sarcoma that arises from the dermis of the skin. It tends to grow slowly and often appears as a firm, raised patch or plaque that may be flesh-coloured or slightly red / purple. Although DFSP rarely spreads to distant organs, it is known for a high recurrence after treatment if not surgically excised with wide margins.