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Oncology > Skin oncology > Flashcards

Skin oncology Flashcards

1
Q

What are the two types of skin cancers

A

Non melanoma
Melanoma

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2
Q

What are the risk factors of skin cancer

A

UV radiation, exposure to ionizing radiation, immunosuppression, inherited disorders, chemical exposure, chronic irritation

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3
Q

What are the inherited disorders of skin cancer

A

Xeroderma pigmentosum
Epidermolysis bullosa
Albinism
Basal cell neveus syndrome (gorlin’s syndome)

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4
Q

What is the high risk region

A

H zone : embryonal fusion planes where cancers can infiltrate deeply

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5
Q

What are the histopathologies of skin cancer

A

Basal cell carcinoma 65%
Squamous cell carcinoma 35%
Melanoma 1-2%

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6
Q

Name the layers of the epidermis from superficial to deep

A

Corneum (squames)
Granulosum (keratohyalin granules)
Spinosum (desmosomes)
Basale (germinal)

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7
Q

Examples of premalignant lesions

A

Actinic keratosis
Bowens disease
Keratocanthoma

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8
Q

What is each premalignant lesion’s likleyhood of progression to SCC

A

Actinic keratosis: 1-20%
Bowen’s disease: 3-5%

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9
Q

How long is the dermis and what does it contain

A

1-2 mm
- lymphatics, nerves, connective tissue, blood vessels, and sweat glands

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10
Q

What are the layers of the skin

A

Epidermis, dermis, subcutaneous tissue

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11
Q

What are the treatment options for actinic keratosis

A
  • cryotherapy
  • curettage
  • topical 5 FU
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12
Q

How does keratoacanthoma progress

A

Grows rapidly for 1-2 months then involutes by 3-6 months spontaneously

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13
Q

What is the treatment for keratocanthoma

A

Surgery

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14
Q

What does ABCDE stand for in detection for early melanoma

A

Asymmetry, borders , colour, diameter, evolving

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15
Q

What percentage of basal cell carcinoma occur on face

A

70%

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16
Q

What are the clinical presentations of basal cell carcinoma and each of their percentages

A

Nodular: 50-60%
Superficial: 30%
Morpheaform / sclerosing : 5-10%

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17
Q

What are the rare histologies for basal cell carcinoma

A
  • micronodular
  • infiltrating
  • basilosquamous
  • keratosis
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18
Q

Describe the appearance of nodular BCC / ulcerative

A

Pearly
Central ulceration
Heaped up boarders
Translucent

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19
Q

Describe the appearance of superficial BCC

A

Scaley macules with indistinct margin

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20
Q

Describe the appearance of morphia form / sclerosing BCC

A
  • flat, indurated ill defined macule with shiny surface that become depressed as they grow . Whitish firm plaque with somewhat distinct margins
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21
Q

Describe the appearance of a solitary lesion

A
  • bright red lesion
  • detected with side lighting
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22
Q

What is the treatment for keloids

A

Surgically with radiotherapy

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23
Q

What is the percentage of recurrence with keloids without radiotherapy

A

50-80%

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24
Q

What is the treatment procedure regime for keloids

A
  • 2cm margin around the new scar
  • 800 cry x 2 with two days in between
25
Q

What are examples of management of non melanoma skin cancers

A
  • cryotherapy
  • electrosurgery
  • topical treatment
  • radiation therapy
  • Moh’s surgery
  • surgical resection
26
Q

What are the advantages and disadvantage of cryotherapy

A
  • quick
  • cost effective
  • excellent cosmetic result
  • no anathema required
  • high cure rate for appropriate indications
  • well tolerated by patients

Disadvantage: no histology confirmation of margins

27
Q

Describe the treatment for melanoma

A
  • wide local excision for primary tumours
  • lymph node assessment if indicated
  • radiotherapy for palliation (since it is radioresistant)
  • systemic therapy (immunotherapy)
28
Q

What is the stand off effect

A

Distance between patient skin and applicator/cone that results in significant dose fall off depending on the size of the tumour. Lesion is below the skin surface

29
Q

How do we compensate for the standoff effect

A
  1. Compensator
  2. Increase SSD
30
Q

Describe the difference between positive and negative stand off

A

Positive : lesion is below the surface of the skin and SSD is longer. Decrease dose rate at the surface
Negative : lesion is above the surface of the skin and SSD is shower.

31
Q

What are some solutions to the standoff effect

A
  1. Changing prescription point
  2. Using compensating filter such as aluminum or foil (more)
  3. Using extended SSD (but increases treatment time)
32
Q

What are the advantages and disadvantages of Moh’s surgery

A
  • high cure rate > 90%
  • spares normal tissue
  • dis: more time consuming and expensive
33
Q

When is Mohl’s surgery used

A

Primary or recurrent SCC and BCC with high risk features

34
Q

How do you increase electron beam surface dose

A

Use a bonus of 0.5-1cm (decreases dose at depth)
Use a tantalum mesh (dose not affect dose at depth)

35
Q

Characteristics of electron beams

A
  • low energy electrons ; Isidore curves show some bulging
  • high energy electron: isotope curves constrict
  • surface dose increases as energy increases
36
Q

What are the advantages of electron treatment

A
  • direct energy deposition as they travel through the medium
  • rapid dose fall off, dose is deposited at the surface
  • minimal dose deposited at depth (end of practical range)
  • more homogenous distribution over a large diameter tumour (greater than 8-10cm)
37
Q

What are the advantages of electron treatment

A
  • direct energy deposition as they travel through the medium
  • rapid dose fall off, dose is deposited at the surface
  • minimal dose deposited at depth (end of practical range)
  • more homogenous distribution over a large diameter tumour (greater than 8-10cm)
38
Q

How big is electron penumbra and when does it increase

A
  • about 1 cm
  • decreased electron beam energy
  • increased field size
  • increase distance from applicator
39
Q

What are common dosage fractionations

A

35gy in 7 fractions
45gy in 10 fractions
50gy in 20 fractions

40
Q

What are the characteristics of orthovoltage

A
  • low energy x ray
  • 75-300 kv
  • 100% surface dose
  • narrow penumbra (1-3mm)
  • easy to shield
41
Q

What are the diagnostic procedures for BCC SCC and melanoma

A

History and physical
Biopsy

42
Q

What are the staging tests for SCC and melanoma

A

BCC (unlikely)
SCC - full dermatologic exam and palpation of draining LNs
Melanoma - sentinel LN, U/S of LNs

43
Q

TNM staging for BCC and SCC

A

T : size and extent/invasion
N: size, number and location (ipsilateral and contralateral)
M : presence or absence of distant Mets

44
Q

TNM staging of melanoma

A

T: tumour thickness and b sub staging refers to ulceration
N: number of lymph nodes
M: sub divided into M1a, M1b, M1c

45
Q

What is the primary treatment for ALL skin cancers (BCC, SCC, melanoma)

A

Surgery

46
Q

What are the radiation doses for BCC and SCC

A

35/7 , 45/10, 50/20
But also dependant on location depth and size

47
Q

Role of systemic therapy in BCC and SCC

A

Not used - unlikley that it has gone beyond regional lymphnodes

48
Q

What is the role of radiotherapy in BCC and SCC

A
  • adjuvant
  • definitive (primary)
    Depends on patient factor and tumour factors
49
Q

What is the role of radiation therapy in melanoma

A
  • palliative (since it is radioresistant)
  • or extra coal spread, large nodes, > 3 LNs, cervical nodes
50
Q

What is the typical dose for melanoma

A

50/25

51
Q

What is the dosage for keloids

A
  • 16 Gy / 2 fx with 2 days apart (the day after surgery)
52
Q

What is the percentage of recurrence of keloids after surgery

A

50-80%

53
Q

What is the F factor

A

Value used to calculate dose in any material from exposure that is measured in air
(Mass energy coefficient for the material divided by the mass energy coefficient for air)

54
Q

What is the clinical implication of F factor

A

Bone absorbs more dose with orthovoltage treatment which raises theoretical risk of development of osteoradionecrosis (severe bone damage)

55
Q

What does F factor depend on

A

Size of field and previous irradiation

56
Q

Where do constrictions and bulging out occur at the isodose lines

A

< 70 %, < 50%

57
Q

What is the rate at which electrons lose energy

A

2 MeV / cm

58
Q

How do you calculate the minimum thickness of lead required for adequate blocking (5% transmission)

A

= Energy (in MV) / 2

Oncology (6 decks)

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