Squamous Cell Carcinoma
Squamous cell carcinoma of the scalp of an elderly man. The crust has probably been removed prior to photography. Used with kind permission from Stuart Waterston and the University of Aberdeen.
This shows a small cutaneous horn on the arm of an elderly gentleman. These lesions are usually caused by underlying SCCs, although BCCs, Paget's disease or infective causes can also rarely cause the lesions. Note the signs of sun damage to the skin around the lesion. Tenderness at the base of large lesions favour the diagnosis of malignancy, although no clinical sign is completely accurate.
This shows a large lesion on a cheek of an elderly gentleman which displays several characteristics of a Keratoacanthoma. However, the chronic nature and slow growth of the lesion marked it out as a malignant lesion. When the lesion was removed and sent to the pathologists, it transpired that the lesion was in fact a malignant melanoma. This case highlights the diagnostic difficulty presented by malignant skin lesions.
This lesion displays some of the characteristic features of a SCC. There is a raw, bleeding area with an irregular border and infiltration beyond the visible margin of the lesion. This lesion had been present for some time.
Probable Squamous cell carcinoma of the outer aspect of the ear helix. The differential for this would be a Basal cell carcinoma due to the occasionally pearly appearance of the lesion edges. Given the site of the lesion and the fact that it can be seen to infiltrate well beyond the ulcerated, visible margin, it is highly probable that this is a SCC.
This is a SCC arising from chronic ulceration of the leg due to venous insufficiency. This type of ulceration must usually be present for many months before malignant change becomes a possibility.
This lesion, on the dorsum of the hand, displays a keratinic horn. The horn, asymmetrical border and induration around the lesion all support the diagnosis of SCC.
This lesion, again on the dorsum of the hand, displays a raw surface, with some remaining crust still visible at the edge of the skin margins.
The lower lip is a common site for SCCs. This is part due to sun exposure on the lower lip as well as the increased contact with tar and carcinogens from cigarettes in smokers. This lesion required an extensive reconstructive procedure, resulting in a degree of microstomia and post operative ulceration from the teeth underneath the flap. Given the size and location of the lesion, some functional problems were to be expected.
This is the same lesion as shown above shown from a more lateral view. Here it can be seen that the lesion protrudes from the lip and has irregular borders. The induration around the lesion is also visile on this photograph.
This SCC arose in an area of an incompletely excised naevus sebaceum. Although BCCs more commonly arise from naevus sebaceum, this lesion was found to be a SCC on histology.
This lesion has the irregular border and indurated surrounding erythematous tissue typical of an SCC. Note the keratinic crust overlying the lesion.
Proliferative lesion on scalp of elderly man with sun damaged skin - clinically SCC.
Proliferative lesion on leg of elderly man with sun damaged skin - clinically SCC.
Features
Squamous cell carcinoma (SCC) is defined as "a malignant tumour arising from the keratinocytes of the epidermis". This is a malignant tumour, with the ability to metastasize. Roughly 3% of people who present with SCC will already have nodal metastasis.
Clinically, the first sign of malignancy is induration of the skin. The lesion itself may be plaque like, ulcerated or verrucous and is always firm on palpation. The border is usually irregular, asymmetrical and hard to define, with infiltration beyond the visible border of the lesion. The margin is opaque and usually erythematous, often with a red-yellow discolouration. Longer standing lesions may become papillary and display a superficial crust which can become detached, leaving a raw, bleeding area.
SCCs can sometimes underlie an outgrowth of tough epithelium known as a cutaneous horn. This is shown in Figures 2 and 7.
Some SCCs infiltrate deeply into the tissue and involve the peri-neurium. These tumours are very difficult to dissect without causing extensive local destruction.
Incidence
SCC is the second most common type of skin cancer.
Much more common in white races, especially in areas of high sun exposure. A Welsh study has found the incidence of non-melanoma skin cancer (NMSC) to be 173.5 per 100,00 in 1988 and 265.4 per 100,000 population per annum 10 years later. Non-melanoma skin cancer encompasses BCC and squamous cell carcinoma, with 20% NMSCs being SCCs.
Those with dark skin are much less at risk. SCC is more common in men (3:1).
Aetiology
SCCs are caused by a malignant change in keratinocytes. Risk factors for developing a SCC include:
- Older age
- Chronic UV exposure
- Burns / old scars displaying new changes
- Chronic radiant heat exposure (erythema ab igne)
- Actinic keratosis / sun damaged skin
- Bowen's disease
- Chronic granulomas, especially long standing venous ulcers (usually several years)
- Tar exposure / treatment
- Certain genetic conditions pre-dispose (such as Xeroderma pigmentosum)
Differential diagnosis
Keratoacanthoma. Inflammatory ulcer. Amelanotic malignant melanoma. Basal cell carcinoma. Chondrodermatitis nodularis helicis.
Diagnosis
Diagnosis is confirmed by excision biopsy and histology.
Referral
Suggested referral pattern for Squamous Cell Carcinoma
Prognosis
Most people who have SCCs removed experience no further problems. However, metastasis can occur.
Factors that influence metastatic potential include:
- Anatomical site - SCC in certain parts of the body predispose more to metastasis than others. The lowest risk is in sun-exposed sites excluding lip and ear. The highest is from SCC which has arisen in areas of radiation or thermal injury, chronic inflammation or Bowen's disease.
- Size - Tumours with a diameter of >2cm are twice as likely to recur locally (15.2% compared to 7.4%), and three times as likely to metastasize (30.3% compared to 9.1%) than tumours <2cm. Lesion depth is also an important prognostic indicator. If depth is >4mm (or the tumour extends down to subcutaneous tissue), then the metastatic rate is 45.7% compared with thinner tumours. Conversely, if the tumour is <4mm (or confined to the upper half of the dermis) then metastatic rate is 6.7%, with recurrence being less likely following treatment.
- Rate of growth
- Aetiology
- Degree of histological differentiation - Poorly differentiated tumours have a poorer prognosis, with more than double the recurrence rate and triple the metastatic rate of a better differentiated SCC. Tumours with perineural involvement also have a poorer prognosis.
- Host immunosuppression - These patients have a poorer prognosis. SCCs in this group of patients tend to be more locally invasive and metastasize more readily.
Treatment
Several treatment options exist for SCCs. Generally speaking though, surgical excision is the treatment of first choice for cutaneous SCC. This yields tissue which can be sent for histology, confirming the diagnosis of SCC as well as providing more detailed prognostic information. Current recommendations are margins of ≥4mm for low risk tumours and ≥6mm for high risk tumours.
Moh's micrographic surgery may be useful for recurrent lesions.
Follow-up
After treatment, patients with SCC still need to be followed up both for local recurrence and for possible nodal involvement.
A suggested follow-up protocol is:
| Type of SCC | Suggested follow-up |
|---|---|
| In situ | Immediate discharge |
| Well differentiated, no other high risk features (see below) | Discharge 6 months |
| High risk (any of): > 2 cm diameter > 4mm depth (excluding keratin) Poorly differentiated Perineural involvement Immunosuppressed patient Recurrent disease Secondary to chronic inflammation | Total 5 year follow up 3/3/6 monthly thereafter |
| Others (e.g. mod differentiated) | 2 years - 6 monthly intervals |
