skin tumours Flashcards
how are meloncytes formed
early in embryogenesis melanoblasts migrate from the neural crest to skin, uveal tract and leptomeninges and once they settle in the skin they form melanocytes
what os the melanocyte:basal keratinocyte ratio
1:5 - 1:10
what is the function of the MC1R protein
determines the balance of pigment in skin and hair
- MCR1 turns phaeomelanin into eumelanin
- one defective copy of MC1R causes freckling
- two defective copies causes red hair and freckles
what are freckles
called ephilides
- patchy increase in melanin pigmentation
what are ‘age’ or ‘liver’ spots called
actinic lentigines
- increase in melanin and basal melanocytes
how does acquired nave come about
during infancy the melanocytes:keratinocyte ratio breaks down at a number of cutaneous sites which allows the formation of simple nave
- very common benign lesions
- low malignant potential
what are junctional naevus
melanocytes proliferate with clusters of cells at DEJ
what are compound naevi
junctional clusters and groups of cells in dermis
what are intradermal navei
all junctional activity has ceased entirely dermal
what is dysplastic navei
- generally >6cm diameter
- variegated pigment
- boarder asymmetry
- architectural atypic and cellular atypia
- unlike melanoma epidermis isn’t effected
what are halo naevi
Have peripheral halo of depigmentation. They show inflammatory regression and are overrun by lymphocytes
what are blue naevi
entirely dermal and consist of pigment rich dendritic spindle cells. The cellular variant may have mitoses and mimic melanoma
what is the aetiology of malignant melanoma
- sunburn
- UV exposure
- genetic risk
what features would make you suspect a melanoma
- change in shape
- new pigmented lesion develops in adulthood
- irregular pigmentation
- bleeding
- development of nodules
- ulceration
what are the 4 main types of melanoma
- superficial spreading (commonest on trunks and legs)
- aural/mucosal lentiginous ( acral and mucosal)
- lentigo maligna (sun damaged face/neck/scalp)
- nodular (varied site but often trunk)
what does a melanoma prognosis depend on
- Breslows depth and ulceration (Breslow = deepest tumour from granular layer)
how do you treat a melanoma
- primary excision to give clear margins
- some also receive a sentinel node biopsy
- if SN positive then you need a regional lymphadenectomy
- chemo, immunotherapy, genetic therapy
what is BRAF
- wild type BRAF is a weak cytosolic proto-oncogene
- if mutated drives cell proliferation regulating MEK and ERK
- range of drugs developed to interfere with this pathway
what are some precancerous dysplasia
- Bowens disease
- Actinic keratosis
- Viral lesions
what are some invasive malignancies
- basal and squamous cell carcinoma
what is seborrhoea keratosis
benign proliferation of epidermal keratinocytes common on the face and trunk. It has a stuck on appearance-greasy hyperkeratotic surface
- epidermal acanthuses, hyperkeratosis, horn cysts
what are the 3 main subtypes of basal cell carcinoma
- nodular
- superficial
- infiltrate (morphoeic)
what are features of basal cell carcinoma
- may infiltrate tissues widely
- prominent desmoplastic fibrous stroma
- margins are poorly defined
- may spread along nerves
- resection may be challenging
what do precursors of squamous cell carcinomas show
dysplasia
