Melanocytic Naevi & Malignant Melanoma Flashcards
What are melanocytic naevi?
Benign proliferation of melanocytes ( a mole)
can be congenital but most are acquired, most commonly during childhood
What is involved in the aetiology of melanocytic naevi?
aetiology is unclear but factors include:
- genetics
- sun exposure
- immune status
more naevi tend to develop in people who are immunosuppressed or exposed to more sun
What are the clinical features of melanocytic naevi?
- can occur anywhere on the body
- more common in fair skinned people
- usually asymptomatic
- flat or raised
- vary in colour, size and shape
What are the 3 ways in which benign naevi can be classified?
- junctional naevus
- compound naevus
- intradermal naevus
What are the characteristics of a junctional naevus?
- melanocytes sit between the epidermis and the dermis (at the junction between the layers)
- flat
- usually mid to dark brown
What are the features of a compound naevus?
- melanocytes sit within the dermis and at the epidermal-dermal junction
- raised centre with a flat surrounding area
- often hairy
- often lighter in colour than a junctional naevus
What are the features of an intradermal naevus?
- melanocytes found within the dermis
- raised
- often hairy
- much paler in colour than other 2 types
- can progress over time from intradermal to compound and then junctional
Outside of the 3 main classifications of naevi, what are 2 common presentations which may be seen?
Blue naevus:
- sits very deep in the dermis giving a dark blue colour
Spitz naevus:
- has a star like pattern with projections around the periphery
What is a potential complication for someone who has many moles?
Someone with >100 moles is at an increased risk of melanoma
this is often familial
What is the treatment for melanocytic naevi?
Usually there is no treatment but patients are asked to monitor their moles and look for any changes
In some situations they may be surgically removed
For what reasons may a mole be surgically removed?
- if there is uncertainty to whether it is benign or malignant (often if a mole changes or a new one develops)
- if the mole causes problems (e.g. intradermal moles often catch on clothing and bleed)
- for cosmetic reasons (done privately)
What is melanoma and why does it occur?
Skin cancer of the melanocytes that occurs due to uncontrolled melanocyte proliferation
What are the 3 stages of melanoma?
Melanocytes usually sit along the basement membrane of the epidermis
- In-situ melanoma involves the epidermis only
- Invasive melanoma occurs when melanocytes spread to the dermis
- Metastatic melanoma occurs when it spreads elsewhere away from the skin
What is the epidemiology of melanoma like worldwide?
- around 3% of skin cancers
- rare in children
- highest worldwide incidence rate in australia
What are the statistics like for melanoma in the UK?
- 5th most common cancer
- accounts for 4% of cancer cases
- incidence is increasing
What is an amelanotic melanoma?
a melanoma containing no pigment
this can be difficult to diagnose as it appears as a bland-looking pink plaque
What are the characteristics of a superficial spreading melanoma?
- most common type
- grows horizontally within the epidermis (doesn’t tend to be growing as aggressive deeply)
- associated with intermittent high intesity UV exposure
- often on the legs
What are the characteristics of Lentigo Maligna melanoma?
- it grows horizontally
- common in the elderly
- associated with long term UV exposure
- found in areas of high sun exposure such as the face
What are the characteristics of acral lentiginous melanoma / subungual melanoma?
- grows horizontally
- common in the elderly
- found on the palms, soles and nails
