Squamous Cell Carcinoma Flashcards
What is squamous cell carcinoma?
SCC = 2nd most common skin cancer
SCC is derived from keratinocytes like BCC
Higher metastatic potential then BCC
=> invasive disease
=> sometimes metastasise & can be fatal
May arise from solar keratoses or Bowen’s disease
Who is at risk of SCC?
Risk factors for SCC:
=> More common in elderly male patients
=> Previous SCC or another form of skin cancer
=> Actinic keratoses
=> Outdoor occupation or recreation
=> Smoking
=> Fair skin, blue eyes and blond or red hair
=> Previous cutaneous injury, thermal burn, disease (eg cutaneous lupus, epidermolysis bullosa, leg ulcer)
=> Inherited syndromes: SCC high risk in xeroderma pigmentosum and albinism
=> Organ transplant recipients have a massively increased risk of developing SCC.
Other risk factors include:
=> ionising radiation
=> exposure to arsenic
=> immune suppression due to disease (eg chronic lymphocytic leukaemia) or medicines
What causes SCC?
> 90% of SCC associated with DNA mutations
=> Mutations in p53 tumour suppressor gene caused by exposure to UVB
=> Other mutations related to cigarette smoking, ageing and immune suppression i.e.azathioprine
=> Mutations in signalling pathways affect the epidermal growth factor receptor, RAS, Fyn, and p16INK4a signalling.
What are the clinical features of SCC?
Enlarging scaly or crusted lumps
Usually arise within pre-existing actinic keratosis or intraepidermal carcinoma
Grow over weeks to months
May ulcerate
Tender / painful
Located on sun-exposed sites i.e. face, lips, ears, hands, forearms and lower legs
Size varies from a few millimetres to several centimetres in diameter
What are the types of SCC?
Distinct clinical types of invasive cutaneous SCC include:
=> Cutaneous horn - the horn is due to excessive production of keratin
=> Keratoacanthoma - a rapidly growing keratinising nodule that may resolve without treatment
=> Carcinoma cuniculatum (verrucous carcinoma) - slow-growing, warty tumour on the sole of the foot.
The pathologist may classify a tumour as well differentiated, moderately well differentiated, poorly differentiated or anaplastic cutaneous SCC.
How is SCC classified?
SCC is classified as low-risk or high-risk depending on the chance of tumour recurrence and metastasis.
Characteristics of high-risk SCC include:
=> Diameter >2cm
=> Location on the ear, vermilion of the lip, central face, hands, feet, genitalia
=> In elderly or immune suppressed patient
=> Histological thickness >2mm, poorly differentiated histology, or with the invasion of the subcutaneous tissue, nerves and blood vessels
=> Metastatic SCC found in regional lymph nodes (80%), lungs, liver, brain, bones and skin
How is SCC staged?
Tumour staging for SCC:
T0: No evidence of a primary tumour
Tis: Carcinoma in situ
T1: Tumour ≤ 2cm without high-risk features
T2: Tumour ≥ 2cm; or; Tumour ≤ 2 cm with high-risk features
T3: Tumour with the invasion of maxilla, mandible, orbit or temporal bone
T4: Tumour with the invasion of axial or appendicular skeleton or perineural invasion of skull base
Nodal staging for cutaneous SCC:
N0: No regional lymph node metastasis
N1: Metastasis in one local lymph node ≤3cm
N2: Metastasis in one local lymph node ≥3cm; or; Metastasis in >1 local lymph node ≤6cm
N3: Metastasis in lymph node ≥6cm
How is SCC diagnosed?
Clinical diagnosis
Diagnosis + histological subtype confirmed pathologically by diagnostic biopsy or after excision
Patients with high-risk SCC undergo staging investigations to determine spread of disease:
=> Imaging using ultrasound scan, X-rays, CT scans, MRI scans
=> Lymph node or other tissue biopsies
How is SCC treated?
Surgical treatment
=> Excised with a 3–10 mm margin of normal tissue around a visible tumour.
=> A flap or skin graft needed to repair the defect
Other methods of removal include:
=> Shave, curettage, and electrocautery for low-risk tumours on trunk and limbs
=> Aggressive cryotherapy for very small, thin, low-risk tumours
=> Mohs micrographic surgery for large facial lesions with indistinct margins or recurrent tumours
=> Radiotherapy for inoperable tumour, patients unsuitable for surgery, or as adjuvant
How is advanced or metastatic SCC treated?
Locally advanced primary, recurrent or metastatic SCC => multidisciplinary consultation with a combination of treatments
=> Surgery
=> Radiotherapy
=> Cemiplimab
=> Experimental targeted therapy using epidermal growth factor receptor inhibitors
How can SCC be prevented?
=> Careful sun protection - important in ageing, sun-damaged, fair skin, immune-suppressed and those with actinic keratoses or previous SCC
=> Stay indoors or under the shade in the middle of the day
=> Wear covering clothing
=> Apply high protection factor SPF50+ broad-spectrum sunscreens
=> Avoid indoor tanning i.e. sunbeds
What is the prognosis of SCC?
Most SCCs are cured by treatment.
=> cure most likely small lesion treated
=> ~50% of people at high risk of SCC develop a second one within 5 years of the first
=> They are also at increased risk of other skin cancers, especially melanoma
