Skin Cancer

Types of Skin Cancer

Skin cancer is the most commonly diagnosed cancer in Australia and New Zealand, which together have the highest incidence rates globally due to intense ambient ultraviolet radiation. The three major types are basal cell carcinoma, squamous cell carcinoma and melanoma, and these account for most cases. Prolonged and repeated sun exposure is strongly linked to an increased risk of developing skin cancer. Early detection and timely treatment offer the best chance of cure and often allow for smaller and simpler procedures.

Types of Skin Cancer

Basal Cell Carcinoma (BCC)

Overview

Basal cell carcinoma (BCC) is the most common skin cancer. It usually appears on sun-exposed areas such as the face, scalp, ears, and neck. Typical presentations include a pearly or translucent papule, a non-healing sore, a scaly red patch, or a lesion that bleeds easily.

Subtypes

Common subtypes include:

Nodular: pearly or translucent bump with tiny visible blood vessels. The surface may look shiny or waxy, and the lesion often has a rolled edge.
Superficial: red, scaly patches that may look like eczema.
Morphoeic, infiltrative and sclerosing: flat, scar-like areas with poorly defined edges, making them difficult to see.
Pigmented: contains melanin and can mimic melanoma, appearing brown, blue, or black colours.

Morphoeic or infiltrative subtypes have a higher risk of recurrence.

Natural History and Prognosis

BCCs grow slowly and rarely spread (metastasise). However, they can cause local destruction and invade deeper tissues including cartilage and bone if left untreated. Prognosis is excellent with complete surgical excision.

Treatment

Diagnosis of squamous cell carcinoma is made through a skin biopsy, with a punch or shave biopsy chosen depending on the appearance and thickness of the lesion.

Standard excision is with 3-4 mm margins for low-risk BCCs. High-risk or infiltrative subtypes usually require margin that is 5 mm or greater or Mohs micrographic surgery for tissue preservation and margin control. Aim is a clear histological margin to reduce recurrence risk.

Formal staging is rarely required because metastasis is extremely rare. Advanced BCC may require imaging if deep invasion is suspected.

Squamous Cell Carcinoma (SCC)

Overview

SCC often presents on chronically sun-damaged skin, for example, the face, scalp, ears, lips, forearms, hands, and lower legs. The typical lesion is a firm, scaly, crusted or keratotic nodule that may ulcerate. Patients often notice a spot that is tender, thickened, or non-healing.

Types

SCC in situ

SCC in situ, also called intraepidermal carcinoma (IEC) or Bowen’s disease, is the earliest form of SCC, confined to the epidermis. It presents as a slowly enlarging, well-demarcated, scaly, erythematous patch or plaque. The surface is often dry, flaky, and may have crusting.
SCC in situ has no potential to spread while it remains confined to the epidermis, but if left untreated a proportion of lesions will progress to invasive squamous cell carcinoma, with estimated rates of 3-10% and significantly higher risk in immunosuppressed patients. This progression is usually slow, occurring over months to years.

Invasive SCC

The natural history of invasive SCC varies by risk group:

Low-risk SCC:

A low-risk squamous cell carcinoma usually appears as a small, well-defined, scaly or crusted spot or lump on sun-damaged skin that grows slowly over many months. These lesions are often firm but not deeply fixed, and they usually have a more regular shape and clearer edges compared with high-risk tumours. They tend to stay on the surface of the skin without forming deep ulceration or rapidly enlarging, and they rarely cause symptoms such as numbness or pain. Low-risk SCCs are typically found on lower-risk areas of the body such as the trunk, arms, or legs.

High-risk SCC

An SCC is considered high risk if it displays features associated with a greater likelihood of recurrence, local invasion, or metastasis. These include a larger tumour size (typically over 2 cm or over 1 cm on high-risk facial areas), increased depth of invasion (over 6 mm or into fat or deeper structures), and adverse histological features such as poor differentiation, perineural or lymphovascular invasion, or desmoplastic growth. Lesions on high-risk sites such as the ear, lip, scalp, temple, or genital skin, as well as those that grow rapidly, recur after treatment, or arise in chronically inflamed or previously irradiated skin, also carry higher risk. Host factors, particularly immunosuppression, further elevate the chance of aggressive behaviour.

Treatment

Diagnosis of squamous cell carcinoma is made through a skin biopsy, with a punch or shave biopsy chosen depending on the appearance and thickness of the lesion.

Treatment usually involves surgical removal. Low-risk SCCs are typically excised with a 4-6 mm margin of normal skin, while high-risk tumours require wider margins of 6-10 mm or more. Achieving clear margins is essential to reduce the chance of recurrence or spread.

For more advanced or high-risk SCCs, staging investigations may be needed, such as CT scans to assess nearby lymph nodes or PET-CT if distant spread is suspected.

Melanoma

Overview

Melanoma commonly develops as a new or changing pigmented lesion (mole). Patients often notice changes in the lesion that include increasing asymmetry of the lesion, irregularity of the border of the lesion, variation in colour, and increasing diameter. It may evolve by rapidly changing in size, shape, elevation, colour, or symptoms.

Subtypes

Superficial Spreading Melanoma
Superficial spreading melanoma is the most common type and usually starts as a flat or slightly raised, irregularly pigmented patch that spreads outward before invading deeper. It often arises from an existing mole and tends to be found on the back in men and legs in women. Because it grows slowly across the skin surface at first, it is often detected earlier and has a good prognosis when caught promptly.

Nodular Melanoma

Nodular melanoma grows quickly in a vertical fashion, forming a firm, dome-shaped nodule rather than spreading across the skin. It may be darkly pigmented or completely skin-coloured, making it harder to recognise. This subtype often develops over weeks to months and is more likely to be thicker at diagnosis, giving it a higher risk of spreading.

Lentigo Maligna Melanoma

Lentigo maligna melanoma develops from a long-standing, flat, irregularly pigmented patch on sun-damaged skin, usually the face or scalp of older adults. It can grow slowly for years before becoming invasive. Once deeper invasion occurs, it behaves like other melanoma.

Acral Lentiginous Melanoma

Acral lentiginous melanoma appears on the palms, soles, or under the nails. Under the nail it may present as a dark streak that widens over time, and on the palms or soles as a persistent irregular patch. These melanomas are often diagnosed later because these areas are less routinely checked, leading to a higher risk of advanced disease at presentation.

Desmoplastic Melanoma

Desmoplastic melanoma usually appears as a firm, skin-coloured or lightly pigmented lesion on the sun-exposed skin of the head or neck. It is commonly mistaken for a scar or cyst and often shows perineural invasion, which can cause numbness or tingling. Although it is less likely to spread to lymph nodes, it can be locally aggressive and difficult to detect early.

Treatment

Surgical treatment depends primarily on Breslow thickness, ulceration, mitotic activity, and lymph node involvement. Melanoma can metastasise to lymph nodes, lungs, liver, brain, and bone. Diagnosis is generally with an excisional biopsy (although shave biopsies can be used where a deep shave that includes the entire lesion is feasible).

After diagnostic excision, wide local excision is performed based on the thickness of the melanoma (Breslow thickness):

Melanoma in situ: 5-10 mm margins
Thin melanomas (Breslow thickness under 1mm): 1 cm margin
Medium thickness melanomas (Breslow thickness 1–2 mm and 2-4 mm): 1–2 cm margin
Thick melanoma (Breslow thickness over 4 mm): 2cm margin.

‍

Melanoma Staging and Sentinel Lymph Node Biopsy

Staging

When a melanoma is diagnosed, one of the most important steps is determining its ‘stage’. Staging tells us how deep the melanoma is, whether there is any sign it has spread, and what treatments or follow-up are needed. Most of this information comes from the Breslow thickness, which is the measured depth of the melanoma under the microscope. Melanomas that are thicker or have high-risk features such as ulceration or a fast growth rate may have a higher chance of spreading.

Sentinel Lymph Node Biopsy (SLNB)

Sentinel Lymph Node Biopsy (SLNB) For melanomas greater than 1 mm in thickness, or for thinner melanomas with high-risk features, a sentinel lymph node biopsy is often recommended. This is a minor surgical procedure performed at the same time as the wide local excision of the melanoma. Before surgery, a small amount of dye or tracer is injected near the melanoma site. This travels to the first lymph node (or nodes) that would receive drainage from the melanoma, called the sentinel node. This node is then removed through a small incision, and it is examined closely under the microscope to check for any early spread of melanoma cells. Most patients have a negative sentinel node, which is reassuring. If melanoma is found in the sentinel node this information helps guide the next steps in treatment.

The results of the biopsy, along with the melanoma thickness, help determine the melanoma’s stage. Stages I and II indicate melanoma confined to the skin.

Stage III means melanoma has spread to nearby lymph nodes.

Stage IV indicates spread to other parts of the body, which is less common at diagnosis.

This staging information helps the team decide whether you need additional scans or treatment.

Imaging and Further Testing

Most people with early-stage melanoma do not need scans. However, patients with stage III melanoma, a positive sentinel node, or symptoms concerning for spread may need CT, PET-CT, or MRI scans to check for any signs of melanoma elsewhere in the body.

Multidisciplinary Team Care

All patients with high-risk or advanced melanoma are discussed in a multidisciplinary team meeting. This is a specialist meeting that includes dermatologists, plastic surgeons, general surgeons, medical oncologists, radiation oncologists, radiologists, and pathologists. The team reviews your results together and recommends the safest and most effective treatment plan. If the sentinel node is positive or scans show spread, you may be referred to a medical oncologist to discuss additional treatment. Modern melanoma care often involves immunotherapy. These medications have significantly improved outcomes for patients with advanced disease, and your oncologist will tailor treatment based on your stage and overall health.

Other Soft Tissue Cancers

Dermatofibrosarcoma Protuberans (DFSP)

DFSP is a rare, slow-growing skin cancer that begins in the deeper layers of the skin. It usually presents as a firm, thickened patch or plaque that gradually becomes raised or nodular over time. The overlying skin may look reddish, brownish, or scar-like. Although DFSP grows slowly, it infiltrates widely into the surrounding tissue, leading to a high risk of local recurrence if not fully removed. It rarely spreads to distant organs. Diagnosis is made by biopsy, and treatment involves wide local excision or Mohs surgery to ensure complete clearance, often removing tissue down to or including the fascia.

Merkel Cell Carcinoma

Merkel cell carcinoma is an aggressive, fast-growing neuroendocrine skin cancer that often appears as a painless, firm, red-violet or skin-coloured nodule. It typically arises on sun-exposed areas such as the head, neck, and upper limbs, especially in older or immunosuppressed patients. Merkel cell carcinoma has a high likelihood of spreading to lymph nodes and distant sites early in its course. Diagnosis is made via biopsy with immunohistochemical staining. Treatment generally involves wide excision, sentinel lymph node biopsy, and often radiation therapy.

Atypical Fibroxanthoma (AFX)

AFX is a rare, low-grade skin tumour that usually appears as a rapidly growing, dome-shaped, pink or red nodule, often with ulceration or crusting. It commonly occurs on sun-damaged skin of the scalp, ears, and face in older individuals. Although it looks aggressive clinically and under the microscope, AFX is generally superficial and has a low risk of metastasis, unlike deeper-seated pleomorphic dermal sarcoma (PDS), which behaves more aggressively. Diagnosis is made by biopsy, and treatment typically involves wide local excision or Mohs surgery. Recurrence is uncommon when clear margins are achieved.

Soft Tissue Sarcomas

Soft tissue sarcomas are a group of malignant tumours that arise from connective tissues such as fat, muscle, nerve sheath, or fibrous tissue. They usually present as a painless, enlarging, deep-seated mass that continues to grow over weeks to months. The overlying skin often looks normal initially. Any soft tissue lump larger than 5 cm, deep to the fascia, or rapidly growing should be considered suspicious. Diagnosis typically requires a core needle biopsy, followed by MRI to define local extent and CT of the chest to assess for lung metastases. Treatment includes wide surgical excision at a specialist sarcoma centre, often combined with radiotherapy for high-grade or large tumours.

Skin Cancer

Types of Skin Cancer