Skin cancer

pathophysiology (melanoma, non-melanoma)

What are the main types of skin cancer?

• Malignant melanoma

• Basal cell carcinoma

• Squamous cell carcinoma

What is malignant melanoma?

Malignant tumour that arises from melanocytes in the basal layer of the epidermis.

• its is a rapidly progressing, metastatic form of cancer

What are some risk factors of melanoma?

• Patient/family history of skin cancer

• Pale skin (Fitzpatrick skin type I and II)

• high density of freckles, large number of moles

• light coloured eyes/ hair

• history of sunburn/ use of sunbeds

• increasing age

• outdoor occupation

How is the growth of melanomas described?

• In situ

• Invasive

• Metastatic

In situ melanoma

Tumour confined to the epidermis

Invasive melanoma

Tumour spread into dermis

Metastatic melanoma

Tumour has spread to other tissues

What are the 4 subtypes of melanoma?

• superficial spreading melanoma

• nodular melanoma

• lentigo melanoma

• acral lentiginous melanoma

Superficial spreading melanoma

• The most common type of melanoma

• Often has a longer in situ phase (months to years)

• Initially grows horizontally (radial growth phase), presenting as a flat, irregularly pigmented lesion that slowly enlarges

• May later develop vertical invasion

Nodular melanoma

• A more aggressive subtype

• Typically grows vertically, presenting as a rapidly enlarging nodule (weeks to months)

• May bleed or ulcerate

Lentigo melanoma

• Lentigo maligna is an in situ precursor lesion related to cumulative sun damage

• Presents as a slowly enlarging patch that becomes increasingly atypical over time, often over years

Acral lentiginous melanoma

• Arises on the palms, soles or under the nails

• Often presents as a slowly enlarging, variably pigmented macule

• May be diagnosed later due to its location

ABCDE criteria

A) asymmetrical shape

B) border - irregularity, poorly defines margins

C) colour change and variation

D) diameter

E) evolving - change in shape, size or colour

Breslow thickness

Measures the thickness of invasive melanoma in mm from the granular layer of the epidermis

what is the main treatment for melanoma?

Surgical management - wide local excision

What are the systemic treatments available for melanoma?

Targeted therapy may be used in some patients with BRAF V600 mutation-positive melanoma (often using combinations of BRAF and MEK inhibitors).⁸

Immunotherapy (for example, anti-PD-1 therapy, sometimes in combination with anti-CTLA-4 therapy) may be offered for advanced disease and in some adjuvant settings, depending on stage and suitability.⁸

Chemotherapy or best supportive care may be considered for advanced melanoma where other treatments are not suitable or have not been effective.

What is basal cell carcinoma (BCC)?

The most common type of cancer in the world.

• non-melanoma form of skin cancer developing very slowly in upper layers of the skin, rarely metastasising

• It is a neoplasm of the non-keratinising cells of the basal layer of epidermis

How does latitude impact BCC incidence?

Higher incidence in areas with low geographic latitude (Australia = highest incidence)

What mutations do BCCs develop from?

Mutations in PTCH and TP53 genes, affecting the basal layer of the epidermis

what are some risk factors for BCC?

• Exposure to UV radiation

• fair skin prone to sunburn

• history of skin cancer

• ionising radiation