17 - Melanoma

Question 1

Melanoma

Answer 1

A malignant tumour derived from melanocytes (cells responsible for melanin production)

Question 2

How common is melanoma

Answer 2

4th most common cancer in aus

Question 3

Strongest risk factors for melanoma

Answer 3

• Family history
• Large numbers of benign or atypical naevi
• Previous melanoma

Question 4

Other risk factors for melanoma

Answer 4

• Immunosuppression
• Sun sensitivity
• Exposure to UV radiation

Question 5

Clinical features of benign naevus

Answer 5

Small, well circumscribed, even colour

Question 6

Histological features of benign naevus

Answer 6

• Symmetrical
• Round to oval, even nuclei
• Cells predominantly in nests
• “maturation” as the cells get deeper

Question 7

Melanoma features

Answer 7

• Asymmetrical
• Border irregularity
• Colour variability
• Diameter
• Evolving

Question 8

Types of extension n into the upper levels of the epidermis seen in a melanoma

Answer 8

Pagetoid spread and “buckshot” scatter

Question 9

Radial growth phase

Answer 9

• Refers to growth within the epidermis (“melanoma in situ”) as well as “microinvasion” into the superficial dermis
• Microinvasive component is limited to single cells and
  small nests
• Lacks metastatic potential

Question 10

Vertical growth phase

Answer 10

• Invasive melanoma within the dermis
• Larger than the epidermal nests
• Mitotic figures
• Implies a capacity for metastatic spread

Question 11

Prognostic indicators of melanoma

Answer 11

• Tumour thickness
• Level of invasion
• Ulceration
• Mitotic rate
• Lymphovascular or perineural invasion
• Satellite lesions

Question 12

Regression

Answer 12

Destruction of the melanoma cells by the body’s immune system

Question 13

Spitz Naevus

Answer 13

A BENIGN LESION WHICH CAN BE MISTAKEN FOR MELANOMA MICROSCOPICALLY

Question 14

Dysplastic naevus

Answer 14

• Larger than benign naevi
• Irregular borders
• Variable colouration
• Some patients develop large numbers of dysplastic naevi (dysplastic naevus syndrome)

Question 15

Gene that is commonly mutated in melanoma

Answer 15

BRAF

Question 16

BRAF

Answer 16

• Serine-threonine kinase
• Most mutations found in the kinase domain
• Caused by point mutation glutamate –> Valine

Question 17

Important and early event in melanocytic neoplasia

Answer 17

• Mutation of BRAF and activation of the MAPK pathway
• Not sufficient for the development of melanoma (other mutations are required)

Question 18

Why do we test for BRAF mutations

Answer 18

Specific BRAF inhibiting drugs have been developed
which are selective for the V600E mutation.

Question 19

Downside of targeting BRAF mutation

Answer 19

• Darwinian selective pressure
• If tumour is BRAF mutated, some clones may not be reliant on BRAF mutation
• If all cells with BRAF mutation are killed, the ones with other mutation will come back

Question 20

Common skin cancers besides melanoma

Answer 20

• Basal Cell Carcinoma
• Actinic Keratosis
• Intraepidermal squamous cell carcinoma
• Invasive squamous cell carcinoma

Question 21

Basal cell carcinoma

Answer 21

• 70% of skin cancer
• High probability subsequent lesions
• Rare genetic predispositions (Gorlin’s syndrome)
• Locally aggressive

Question 22

Actinic keratosis

Answer 22

• Dysplastic proliferation of keratinocytes
• Occurs on sun exposed sites, fair skin, elderly

Question 23

Intraepidermal squamous cell carcinoma (bowen’s disease)

Answer 23

• Erythematous plaque
• Sun-exposed or sun-protected skin
• Cytological atypia

Question 24

Squamous cell carcinoma

Answer 24

• Sun damaged skin
• Tenderness, “thickness” on palpation
• Low risk of metastasis

Question 25

Risk factors of SCC

Answer 25

• Perineural invasion
• poorly differentiated grading

Question 26

Keratoacanthoma

Answer 26

• Type of SCC
• Rapidly growing
  crateriform lesion
• Usually involutes