Squamous Cell Carcinoma

Definition/diagnostic criteria Squamous cell carcinoma (SCC) is a common form of non-melanoma skin cancer that originates in the squamous cells of the epidermis, the top layer of the skin. SCC typically presents as an indurated, scaly plaque or nodule with variable erythema and ulceration.

To diagnose SCC, GPs should consider the following diagnostic criteria:

• Clinical presentation: SCC often appears as a persistent, non-healing ulcer or a scaly, crusted lesion. It can be firm to the touch and may have a tendency to bleed. SCC may resemble other skin conditions such as actinic keratosis or eczema, so a thorough evaluation is crucial.
• Biopsy: To confirm the diagnosis, a skin biopsy is recommended. This involves removing a sample of the affected tissue and sending it for histological examination. The biopsy should include the entire lesion’s thickness to determine the presence of invasive SCC.

Epidemiology SCC accounts for approximately 20% of all skin cancers diagnosed in the UK, making it the second most common type after basal cell carcinoma.

• Major risk factors for SCC include chronic sun exposure, fair skin, a history of sunburns, immunosuppression and previous radiation therapy.
• SCC primarily affects individuals over 50 years old, and it is slightly more common in men than in women.
• SCC is the most common type of skin cancer in skin of colour, although its prevalence is significantly less than in white skin.

Diagnosis
Clinical features: Recognising the clinical features of SCC is crucial for early diagnosis:

• Location: SCC commonly arises on sun-exposed areas such as the face, ears, neck and the back of the hands. It can also occur on mucous membranes and genitalia. In skin of colour the most commonly affected sites are the head and neck (including hair-covered areas of the scalp), the legs and feet, and the anogenital skin
• Appearance: SCC lesions typically present as thick, scaly, or crusted plaques or nodules. They may exhibit rapid growth, bleeding or ulceration.
• Pain or itchiness: Some patients may experience pain or itching at the lesion site.

Investigations

• Skin biopsy: A skin biopsy is the gold standard for diagnosing SCC. Histopathological examination reveals atypical keratinocytes infiltrating the dermis, confirming the diagnosis.
• Imaging: In cases where SCC is suspected to have invaded deeper tissues, imaging studies such as ultrasound, CT scans, or MRI may be necessary to assess the extent of the lesion and lymph node involvement.

Treatment Management of SCC depends on several factors, including the tumour’s size, location and depth of invasion, as well as the patient’s overall health. Treatment options may include:

• Excision: Surgical excision is the primary treatment for SCC. This involves removing the tumour along with a margin of healthy tissue to ensure complete removal.
• Mohs micrographic surgery: For high-risk or complex lesions, Mohs surgery is recommended, as it offers the highest cure rates while minimising tissue loss.
• Radiotherapy: In cases where surgery is not suitable, radiotherapy may be considered, especially for elderly or frail patients.
• Topical therapy: Superficial SCCs can be treated with topical therapies like imiquimod or 5-fluorouracil cream.
• Systemic therapy: In cases of metastatic SCC or when regional lymph nodes are involved, systemic therapy with chemotherapy or immunotherapy may be required.

Prognosis The prognosis for SCC largely depends on the stage at diagnosis and the choice of treatment. When detected and treated early, SCC has an excellent prognosis, with a cure rate exceeding 90%. However, if left untreated or diagnosed at an advanced stage, SCC can become invasive and potentially metastasize to lymph nodes or distant organs, significantly reducing survival rates.