Photocarcinogenesis Flashcards
Bullous impetigo
blistering at site of infection
Caused by staphylococcus toxin A
Staphylococcal scalded skin syndrome
Caused by staphylococcus toxin B
Most common in children
Low mortality rates
Organism usually causing cellulitis
Beta haemolytic strep
Another name for basal cell papilloma
Seborrhoeic wart
Appear as firm, elevated pigmented nodules which may feel like a button in the skin
They are often found on the legs and commoner in females
There may be a history of trauma or insect bite
Dermatofibroma
Keratoacanthoma
Rapidly growing epidermal tumours which develop central necrosis and ulceration
They occur on sun exposed sites and can grow to 2-3cm across
Whilst they may resolve spontaneously, best to surgicaly remove as they can mimic squamous cell carcinoma
Where does Bowen’s disease most commonly develop?
Lower womens legs
Where would you usually develop a pilar cyst?
The scalp
Key characteristics or “hallmarks” of cancer
- Insensitivity to growth signals
- Insensitivity to anti-growth signals
- Evade death (apoptosis)
- Limitless potential to divide
- Angiogenesis
- Invasion and metastasis
Basal cell carcinoma and exposure
Intermittent exposure
Squamous cell carcinoma and exposure
Chronic exposure
Melanoma and exposure
Intermittent exposure
Lattitude and skin cancer
Incidence increases closer to equator
Skin colour and eye colour and cancer
Red/fair haired individuals with blue eyes and freckling
Where would patients with Xeroderma pigmentosum (XP) develop skin cancer?
Skin exposed areas
UVC wavelength
200-280 nm
UVB wavelength
280-315 nm
UVA wavelength
315-400 nm
Visible light spectrum
400-700 nm
UV signature mutation
Cytosine to thymine (at dipyrimidine sites)
NER
Nucleotide excision repair
BER
Base excision repair
DSB
Double strand break repair
MMR
Mismatch repair
Which UV is mainly responsible for initiating mutations?
UVB
Which UVs are responsible for promoting mutations etc
UVB/UVA
Estiamted action spectrum for cancer in humans?
298nm
Age onset of MM?
<20 years
Merkel cell skin cancer exposure
?cumulative
HPV associated with which types of skin cancer?
BCC and SCC
Metastases common in which type of cancers?
MM and MCC
malignant melanoma and merkel cell carcinoma
Most common site for BCC?
Face and 1/3 sun protected sites
Main site for SCC?
Sun exposed sited
Main sites for malignant melanom?
Face, legs, back
Main site for MCC?
Head/neck, sun exposed sited
BCC formed from which type of cell?
Keratinocytes
Major risk factor for BCC?
Immunosuppression (x10)
This is even BIGGER risk factor in SCC (65-250x)
Eating this poison can increase risk of BCC?
Aresenic
-same for SCC
Syndromes predisposing to BCC?
XP
Basal cell nevus syndrome (Gorlin syndrome)
BCC risk factors
Intermittent sun exposure/sunburn Immunosuppression (10x)
Ionizing radiation
Arsenic ingestion
?photosensitising drugs Family/personal history of BCC/SCC
SCC precursor lesions
Actinic keratoses
Bowen’s disease
Risk factors for SCC?
Chronic/cumulative sun exposure. Sunbeds.
Immunosuppression (65-250x)
Arsenic /petroleum products/organophosphates/smoking/scars/HPV ?photosensitising drugs
Family/personal history of BCC/SCC
SCC predisposing syndromes
XP Rothmund Thomson syndrome Bloom syndrome Werner syndrome Dystrophic epidermolysis bullosa Fanconi anaemia
Precursor lesions for melanoma
Moles
Where are melanomas usually found?
Chest/back (men) Legs (women) Palms and soles Growing under the nails Eyes
Risk factors for melanoma
Risk factors:
Intermittent sun exposure/sunburn. Sunbeds
Ionizing radiation
Immunosuppression
?photosensitising drugs/?heavy metals/?other occupational exposure Family/personal history of CM/BCC/SCC
Melanoma predisposing syndromes
XP
Atypical mole syndrome
Drugs associated with photocarcinogenesis
Psoralen
Voriconazole
Azathioprine
Vemurafenib
Photosensitising drugs
Immunosuppressants
Topical
UV and langerhans cells
UV reduced number of langerhans cells
UV and oxidative stress
Increases oxidative stress
UV and exogenous compounds
UV interacts with exogenous compounds
UV and IL10 and PGE2
UV upregulates inflammatory mediators including IL10 and PGE2