Naevi

Question 1

what are melanocytic naevi?

Answer 1

moles

Question 2

how do you get melanocytic naevi?

Answer 2

Congenital: only 1% of babies are born with a congenital naevus
• Small = < 2cm diameter
• Medium = > 2cm but < 20cm
• Giant garment type lesions, these large lesions have a 10-15% risk of melanoma
Acquired: most naevi are acquired during the first 2 decades,
during infancy the melanocte: keratinocyte ratio breaks down at a number of cutaneous sites - this allows the formation of simple naevi

Question 3

how do naevus develop?

Answer 3

• Childhood => junctional naevus: melanocytes proliferate, cluster of cells at the DEJ)
• Adolescence/early adulthood => compound naevus: clusters at junction and groups of cells in the dermis
• Adulthood => intradermal naevus => intradermal naevus; entirely dermal

Question 4

What is a simple naevi?

Answer 4

they are very common, benign lesions
average person has 20-30 lesions
low malignant potential

Question 5

What is a dysplastic naevi?

Answer 5

these are usually > 6mm diameter, various pigments, border asymmetry, there are 2 clinical settings:
• Sporadic: not inherited, slightly increased risk malignant melanoma [MM]
• Familial: strong FH of melanoma, autosomal inheritance, high penetrance, lifetime risk of MM (up to 100%)

Question 6

What are the potentially concerning things about dysplastic naevi?

Answer 6

can be architectural atypia AND cellular atypia,
host reaction-fibrosis and inflammation,
the epidermis is NOT effaced (unlike melanoma),
severe dysplasia may be difficult to distinguish from melanoma in-situ.

Question 7

what are halo naevi?

Answer 7

perhipheral halo of depigmentation, shows inflammatory regression,
overrun by lymphocytes

Question 8

what are blue naevi?

Answer 8

entirely dermal,
they have pigment-rich dendritic spindle cells,
cellular variant may have mitoses and mimic melanoma

Question 9

what are spitz naevus?

Answer 9

used to be called ‘benign juvenile melanoma’,
usually in those <20 yrs old,
consists of large spindle and/or epithelioid cells,
usually has prominent vasculature,
most are entirely benign BUT there’s a malignant variant

Question 10

what is an ugly duckling mole?

Answer 10

a mole which is different from the others
look at speed of change
take pictures every year etc
most melanomas arise de novo but some from dysplastic naevi

Question 11

immunosuppressed leukaemic children…

Answer 11

have more naevi

Question 12

malignant melanoma which come from dysplastic naevi

Answer 12

More common in females
Any site but is most common in sun-exposed areas
Rare in childhood, incidence peaks in middle-age
SUSPECT melanoma IF: change in shape, irregular pigmentation, new pigmented lesion develops in adulthood, bleeding, ulceration, development of satellite nodules

Question 13

types of epidermal tumours

Answer 13

benign - seborrhoeic keratosis 
Precancerous dysplasias: 
 - Bowen’s disease, 
 - actinic keratosis 
 - viral lesions 
Invasive malignancies: BCC, SCC

Question 14

what is a seborrhoeic keratosis?

Answer 14

Caused by the benign proliferation of epidermal keratinocytes
Very common in ageing skin

Question 15

where do you find a seborrhoeic keratosis?

Answer 15

• On face and trunk, has a ‘stuck on’ appearance and a greasy hyperkeratotic surface

Question 16

how does a seborrhoeic keratosis present?

Answer 16

epidermal acanthosis,
horn cysts
*The eruptive appearance of many lesions may indicate a internal malignancy (Leser-Trelat sign)

Question 17

What is Bowen’s disease?

Answer 17

SCC in situ

Mostly females, tends to happen in older women, mostly on [lower] legs

Question 18

how does Bowen’s disease present?

Answer 18

Scaly erythematous patch/plaque, irregular border, NO dermal invasion

Question 19

what is actinic keratosis?

Answer 19

Very common, common precursor of invasive SCC
Usually on sun-exposed skin,
variable epidermal dysplasia,
severely atypical lesions are bowenoid
There are always multiple, esp. on head/neck

Question 20

What are viral lesions?

Answer 20

Genital lesions (occurs on anogenital skin) which are often dysplasic
Associated with human papillomavirus: HPV type 16
Erythroplasia of Queyrat-penile Bowen’s

Question 21

where do miscellaneous tumours arise from?

Answer 21

dermis, 
blood vessels, 
nerves, 
sweat glands, 
hair follicles etc. (basically everything e.g. Merkel cells, langerhans cells etc.)