7.5 - Skin cancer Flashcards
What two investigation types are mainly used for neoplastic skin conditions?
- imaging (internal organ involvement, vascular supply)
- skin biopsy (microscopy)
Define melanoma
Malignant tumour arising from melanocytes
What cells do melanomas arise from?
Melanocytes
How deadly is melanoma?
Causes 75% of skin cancer deaths (despite not being the most common type of skin cancer)
Describe the incidence rates of melanoma worldwide.
Rising incidence rates observed worldwide (although mortality is stable)
Where on the body can melanoma arise?
- mucosal surfaces (e.g. oral, conjunctival, vaginal) and within uveal tract of eye
- internal organs can be affected (even by primary melanoma not just metastatic) - probably due to impaired melanocyte migration during embryogenesis
What are central depigmented parts of melanoma lesions due to?
Tumour regression
What are the genetic risk factors for melanoma? (4)
- family history (CDKN2A mutations), MC1R variants
- DNA repair defects (e.g. xeroderma pigmentosum)
- lightly pigmented skin (fairer)
- red hair
What are the environmental risk factors for melanoma? (3)
- sun exposure - intense intermittent, or chronic
- sunbeds
- immunosuppression
What are the phenotypic risk factors for melanoma? (2)
- > 100 melanocytic nevi (moles)
- atypical melanocytic nevi (moles)
How is the molecular pathogenesis of melanoma important clinically? (2)
- genetic mutations in this pathway can predispose to melanoma
- these processes can be targeted therapeutically e.g. BRAF, MEK
Describe the epidemiology of melanoma.
- increasing worldwide
- develops predominantly in Caucasian populations
- incidence low amongst darkly pigmented populations
- 10-19/100k per year in Europe
- 60/100k per year in Australia/NZ
What are the subtypes of melanoma? (5)
- superficial spreading
- nodular
- lentigo maligna
- acral lentiginous
- unclassifiable
How common is superficial spreading melanoma?
60-70% of all melanomas
Which group of people is superficial spreading melanoma most common in?
Fair-skinned
Where is superficial spreading melanoma seen on the body most frequently?
- trunk of men
- legs of women
How can superficial spreading melanoma arise?
Can arise de novo (no previous moles) or in pre-existing nevus (previous mole)
How is regression seen in superficial spreading melanoma and why does it happen?
- in 2/3 of tumours, regression is visible as grey or hypopigmentation/depigmentation
- shows interaction of host immunity against tumour
Describe the growth pattern of superficial spreading melanoma.
- horizontal (or radial) growth phase where you see 4 characteristic features:
- asymmetry (A)
- border irregularity (B)
- colour variation (C)
- diameter increase (D)
- vertical growth phase - leads to appearance of nodule or bump
What is the ABCD rule that you see in superficial spreading melanoma (horizontal growth phase)?
- Asymmetry
- Border irregularity
- Colour variation
- increased Diameter
How common is nodular melanoma?
15-30% of all melanomas
Which groups of people is nodular melanoma common in? (2)
- 2nd most common type of melanoma in fair-skinned individuals
- more common in men than women
Which body parts is nodular melanoma most common in?
Trunk, head and neck
How does nodular melanoma present?
- usually as blue-black, but sometimes pink-red nodule (= a pigmented nodule)
- may be ulcerated, bleeding
- develops rapidly
(Trunk, head, neck)
What does amelanotic mean?
When a nodule has no pigment - always consider nodules even if not brown
Describe the growth of nodular melanoma.
- no horizontal/radial growth phase - features e.g. asymmetry, border irregularity, colour variation are not present/obvious
- only vertical growth phase - invades earlier and tends to present at more advanced stage with worse prognosis (vs superficial spreading)
In nodular melanoma, what does only having a vertical growth phase mean clinically?
It invades earlier and tends to present at more advanced stage with worse prognosis (compared to superficial spreading melanoma)
How common is lentigo maligna?
10% (minority) of cutaneous melanomas
Which groups of people is lentigo maligna most commonly in? (2)
- > 60 years old
- occurs in chronically sun-damaged skin
Where is lentigo maligna most commonly seen on the body?
Most common on face
What does the term ‘lentigo maligna’ refer to?
Pre-invasive, slow growing, asymmetric brown/black macule with colour variation and an irregular indented border
When do we call it lentigo maligna and when do we call it lentigo maligna melanoma?
- in situ - termed ‘lentigo maligna’
- invasive - termed ‘lentigo maligna melanoma’
- 5% of lentigo maligna progresses to invasive melanoma
How common is acral lentiginous melanoma?
Relatively uncommon - 5% of all melanomas
Which group is acral lentiginous melanoma diagnosed most frequently in?
7th decade of life (60s)
Where in the body does acral lentiginous melanoma occur?
Typically occurs on palms and soles OR in/around nail apparatus (melanonychia)
What is the incidence of acral lentiginous melanoma in different racial groups?
- similar across all racial and ethnic groups
- disproportionate % of melanomas diagnosed in Afro-Caribbean (up to 70%) or Asians (up to 45%) - as they do not typically develop sun-related melanomas
How are patients instructed to detect melanomas early?
Look for history of change in colour, shape or size of a pigmented skin lesion
What is the ABCDE public awareness campaign for melanomas?
- Asymmetry - one half does not match
- Border - uneven borders
- Colour - variety of colours
- Diameter - larger than a pencil eraser
- Evolution - change in size, shape, colour etc (most important)
What is Garbe’s rule?
If a patient is worried about a single skin lesion, do not ignore their suspicion and have a low threshold for performing biopsy
How do we diagnose melanoma?
Skin biopsy
What are the differential diagnoses for melanoma? (3)
- basal cell carcinoma - can be pigmented
- seborrheic keratosis - harmless skin lesions that increase in number with age
- dermatofibroma - harmless benign skin tumour
What are poor prognostic features for melanoma? (6)
- increased Breslow thickness >1mm (measured histologically from stratum granulosum downwards to bottom of tumour)
- ulceration
- age
- male gender
- anatomical site - trunk, head, neck
- lymph node involvement
What are the survival rates for melanoma like?
- stage 1A melanoma have 10 year survival of >95%
- thick melanomas >4mm and ulceration (stage pT4b) have a 10 year survival of 50%
What technique do we use to investigate melanoma?
(Alongside biopsy)
Dermoscopy - can improve correct diagnosis of melanoma by nearly 50%