skin cancer Flashcards
What are melanomas?
Malignant tumors arising from melanocytes (pigment cells)
What percentage of skin cancer deaths are caused by melanomas?
75% (but it is not the most common type)
Give a possible reason for the rising worldwide incidence of melanomas.
Might be due to detecting more
What surfaces can melanomas be found on?
Skin, mucosal surfaces (oral, vaginal, conjunctival) and within uveal tract of eye
What are the broad types of risk factors for melanoma?
Genetic factors
Environmental factors
Phenotypic factors
What are some genetic risk factors for melanoma?
Family history (CDKN2A mutation, MC1R variants)
Lightly pigmented skin
Red hair
DNA repair defects (e.g. xeroderma pigmentosum)
What are some environmental risk factors for melanoma?
Intense intermittent sun exposure
Chronic sun exposure
Living in equatorial regions
Sunbeds
Immunosuppression
What are some phenotypic risk risk factors for melanoma?
> 100 melanocytic nevi
atypical melanocytic nevi
What constitutes the MAPK pathway and what does this pathway regulate?
RAS-RAF-MEK-ERK
Regulates cell proliferation, growth and migration
What is the contribution of KIT mutations towards melanoma causation?
30-40% of acral and mucosal melanomas
Also melanomas from chronically sun-exposed skin bear activation mutations and copy number amplifications of KIT gene
In what genes are activation mutations present in?
NRAS genes (15-20% of melanomas)
BRAF genes (50-60% of melanomas)- high in melanomas of skin with intermittent UV exposure but low in melanomas of skin with high cumulative UV exposure
What gene mutations lead to MAPK pathway activation?
BRAF mutation substitution
CDKN2A mutation
What is P16 and what is its functions?
Binds to CDK4/6 and prevents the formation of the cyclin D1-CDK4/6 complex
What is the function of the cyclin D1-CDK4/6 complex?
Phosphorylates Rb, inactivating it and leading to the release of E2F (once released, E2F promotes cell cycle progression
What is the host immunological response to melanoma?
Host CD8+ T cells can recognise melanoma specific antigens and, if activated appropriately, can kill tumour cells
CD4 helper T cells and antibodies also play a critical role
What is CTLA4 and what does it do?
Cytotoxic T-lymphocyte-associated antigen 4 is a natural inhibitor of T cell activation by blocking costimulatory signal (B7b on APC to CD28 on T-cell
What drug classes are associated with melanoma immunotherapy?
CTLA-4 inhibitors (ipilimumab) Checkpoint blockade (PD-1, PDL-1)
What is the distribution of melanoma?
Develops predominantly in caucasian populations
Incidence low among darkly pigmented populations
less per year in Europe than in Australia/NZ (x3 in Au/NZ)
What are the subtypes of melanoma?
Superficial spreading
Nodular
Lentigo maligna
Acral lentiginous
Unclassifiable
What is the most common type of melanoma in fair-skinned individuals?
Superficial spreading (60-70%)
Where are superficial spreading melanomas localised?
Trunk of men
Legs of women
How do superficial spreading melanomas arise?
De novo or from a pre-existing nevus
How is interaction of host immune system with superficial spreading melanoma reflected in the tumor?
Areas of regression (visible as grey, hypo- or depigmentation) in 2/3 of tumours
In a superficial spreading melanoma, what are the growth phases of the tumour?
Slow horizontal (radial) growth phase limited to the epidermis
Rapid vertically oriented growth phase associated with nodule development
What is the second most common type of melanoma in fair skinned individuals?
Nodular
Where are nodular melanomas localised?
Usually head, neck, trunk
What is the gender distribution of nodular melanomas?
M>F
What do nodular melanomas present as and in what stage?
Generally present as blue to black but may be pink to red- may be ulcerated, bleeding
Tend to present more advanced stage with poorer prognosis
Describe nodular melanoma development
Develop rapids
Believed to arise as a de novo vertical growth phase without the pre-existing horizontal growth phase
What type of melanoma accounts for the minority of cutaneous melanomas?
Lentigo maligna
What age group does lentigo maligna arise in?
> 60 years old
Where is lentigo maligna localised?
In sun-damaged skin, most commonly on the face
What does a lentigo maligna lesion look like?
Slow growing, asymmetric brown to black macule with colour variation and an irregular, indented border
What precursor lesion does invasive lentigo maligna melanoma arise from?
Lentigo maligna (in situ melanoma) in sun damaged skin- it has been estimated that 5% of lentigo malignant lesions progress to invasive melanoma
How common is acral lentiginous melanoma and at what age is it usually diagnosed?
Relatively uncommon- 5% of all melanomas
most frequently diagnosed in the 7th decade of life
Where are lesions localised in acral lentiginous melanoma?
Typically occurs in palms, soles and around the nail apparatus
What is the racial/ethnic distribution of acral lentiginous melanoma?
Incidence similar across all racial/ethnic groups
As darkly pigmented Africans and Asians do not typically develop sun-related melanomas, ALM represents a disproportionate percentage of melanomas diagnosed in Afro-Caribbean or Asians
What are amelanotic melanomas?
Melanomas which do not produce melanin, therefore do not look like other melanomas (may appear pink or reddish, with grey or brownish edges)
What is the ABCDE melanoma self detection campaign?
Asymmetry Border irregularity Colour variaton Diameter > 5mm Evolving
What are differential diagnoses for melanoma?
Basal cell carcinoma
Dermatofibroma
Sebborrhoeic keratosis
What are poor prognostic features for melanoma?
Age Anatomical site - head, neck, trunk Ulceration Increased Breslow thickness (>1mm) Lymph node involvement Male gender
stage 1A melanoma has a 10 year survival of 95% but a melanoma with thickness >4mm and ulceration (pT4b) has a 10 year survival of 50%
What is breslow thickness?
Measurement from granular layer to the bottom of tumour
Name a technique used in melanoma investigation
Dermatoscopy- can improve correct diagnosis of melanoma by nearly 50%
What are some global features of melanomas?
Asymmetry
Colour variation
Reticular, globular, reticular-globular, homogeneous
Starbust
Atypical networks, streaks, atypical dots or globules, irregular blood vessels, blue-white veil, regression structures
Can dermatoscopic findings be considered in isolation in melanoma?
No- history and risk factor status are important
Excise lesion for histological assessment if in any doubt
What are the 2 stages of excision in melanoma management?
Primary excision- down to the subcutaneous fat, 2mm peripheral margin
Wide excision- margin determined by Breslow depth (5mm for in situ, 10mm for thickness >=1mm)