Skin cancer Flashcards
what is the most common human cancer?
Skin cancer
what are the risk factors for skin cancer?
genetic predisposition immunosuppression age sun exposure (UV radiation) other environmental carcinogens
where on the body can skin cancer arise?
from basically every area of the skin most commonly from the epidermis and melanocytes
What is melanoma?
cancer which arises from melanocytes found in along the basal layer
more common in older people but can also occur in younger people - most common cancer in 16-25 yr olds
what is the general prognosis of melanoma?
They are much more likely to metastasis than BCC and SCC [keratinocyte skin cancers]
Generally has a bad prognosis, early diagnosis is essential as it’s difficult to treat once it has spread -
survival depends on tumour depth (i.e. prognosis is good if Breslow thickness is <1mm, prognosis is worse if >4mm), thin melanomas are cured
how is melanoma diagnosed?
Asymmetry,
Border,
Colour,
Diameter,
Evolution [i.e. speed of change - red flag e.g. getting darker],
ugly duckling sign - look for the one that looks different esp. in atypical mole syndrome
How is melanoma treated?
primary excision to give clear margins,
sometimes also a sentinel node biopsy -
if SN positive then do a regional lymphadenectomy,
immunotherapy/genetic therapies,
narrow complete excision for confirmation of diagnosis and assessment of breslow:
• If in-situ => 5mm clearance
• If invasive but < 1mm => 1cm clearance
• If invasive but > 1mm => 2cm clearance
• Do SNB (sentinel node biopsy) if > 1mm thick or thinner with mitoses
what are the 4 main types of melanoma?
- Superficial spreading (SSM) => commonly found on trunk and limbs
- Acral/mucosal lentiginous (A/MLM) => acral (toes/fingers etc.) and mucosal
- Lentigo maligna (LMM) => sun-damaged face/neck/scalp
- Nodular (NM) => varied sites but often trunk
SSM, A/MLM and LMM growth
These all grow as macules (radial growth phase [RGP] - either entirely in situ or with dermal micro-invasion) - width
Eventually these melanoma cells can invade the dermis forming an expansive mass with mitosis = vertical growth phase [VGP] - only VGP melanomas can metastasise - depth
NM growth
No RGP, this is a nodule of VGP tumour, may be more aggressive
what determines the prognosis of a melanoma?
the Breslow depth/thickness (= deepest tumour from granular layer [mm] - the thinner the better!)
ulceration [‘b’ = the suffix for ulceration],
adverse prognosis is also indicated by high mitotic rate,
lymphovascular invasion, satellites and sentinel (original cancer) lymph node involvement
what % of skin cancers are melanoma?
5-10% the rest are BCC and SCC
what is basal cell carcinoma BCC?
Very common (about 75% of skin cancers), usually on sun-exposed sites, in middle-aged and elderly (in the UK) Pathogenesis: groups of basal cells (?) invade the dermis, there’s lots of mitosis and apoptosis (peripheral palisading)
How does basal cell carcinoma present?
slow growing lump OR non-healing ulcer, painless (so often ignored), pearly, translucent, visible arborising blood vessels, central ulceration (‘rodent ulcer’) Locally invasive - does not spread
What are the different types of BCC?
scaly plaque (superficial), nodular/nodulocystic (most common), pigmented, infiltrative (morphoeic, prominent desmoplastic fibrous stroma, poorly defined, most aggressive, difficult to completely remove, may spread along nerves = difficult to resect)
How is basal cell carcinoma treated?
surgery can get really bad if left untreated
What is the prognosis of basal cell carcinoma?
death is unlikely - maybe could occur if tumour invades the eye and brain etc.
What is squamous cell carcinoma?
it is less common about 20% of skin cancers - usually in the elderly
Rare associations = xeroderma pigmentosum etc.
Prognosis of SCC?
more likely to cause death than BCC
Low risk SCC: majority, well-differentiated cancer cells
High risk SCC: poorly-differentiated, cutaneous horn
Keratoacanthoma = self-limiting form of SCC
If neglected, may spread - the risk of mets is only 3-5% but once it happens = poor prognosis
Occassionally may get chronic leg ulcers (e.g. stasis ulcers), sites of burns (e.g. sinuses e.g. chronic osteomyelitis), chronic lupis vulgaris
Who gets SCC?
Usually sun-damaged skin (chronic, long-term, UV) Precursor lesions (squamous dysplasia): actinic keratosis, Bowen’s disease, viral lesions (more on all these later) High risk sites for SCC: ear, lip, scalp
how does SCC present?
warty/crusted (hyperkeratoic) lump or ulcer,
grows fast,
may be painful,
may bleed
the types of UV light
UVB (290-320nm) causes direct DNA damage, it is more damaging than UVA when the sun is directly overhead, it can cause sunburn
UVA (320-400nm) causes indirect oxidative damage, it penetrates more deeply into the skin than UVB
UVB and UVA can be blocked by sunscreen, and they can both cause pigmentation and skin cancer/ageing
UVC is blocked by window glass and atmospheric ozone
what is normal cutaneous photosensitivity?
normal sunburn
What is abnormal cutaneous photosensitivity?
abnormal cutaneous response to UV radiation and, in some people, visible light.
