Squamous cell carcinomas (SCCs) are a type of skin cancer which produce keratin.
Risk Factors
- Sun-exposure
- Fair skin, blue eyes, blond/red hair
- Prolonged exposure to carcinogenic materials e.g. tar from cigarette smoke
- Chronic ulcers
- Severe burn scars
- HPV infections
- Immunosuppression: e.g. CLL/drug-induced/secondary to organ transplant
Clinical Features
- Scaling or crusted (keratotic) lesion
- Can be flat, nodular, or plaque-like
- Can potentially ulcerate
- Tend to occur on sun-exposed sites e.g. face, tips of the ears, lips, lower legs, forearms
- Can itch and/or bleed and tend to be painful
- Grow over weeks to months
- Can metastasise (usually local areas/lymph nodes)
Unknown photographer/artist, Public domain, via Wikimedia Commons
Squamous Cell Carcinoma
Differential Diagnosis
- Actinic/Solar Keratosis
- Acitinic keratoses are pre-cancerous lesions which can lead to squamous cell carcinoma if left untreated.
- They appear as scaly and typically erythematous lesions that arise on sun-exposed parts of the body e.g. tips of the ears/bald scalps etc.
- Bowen’s Disease
- Bowen’s disease is a type of ‘squamous cell carcinoma in situ’ i.e. it is confined to the epidermis and has not yet invaded past the basement membrane. They present as slow growing, erythematous and scaly plaques. Biopsy can allow diagnosis of Bowen’s disease as the tumour will be intra-epidermal.
Klaus D. Peter, Wiehl, Germany, CC BY 3.0 DE , via Wikimedia Commons
Bowens' Disease
- Keratoacanthoma
- A keratocanthoma is a locally destructive skin tumour. They grow rapidly and usually form a hard keratin plug, which can later resolve to form a depressed scar. Since it’s difficult to truly differentiate it from an early SCC, they are usually treated as SCCs.
Investigations
Diagnosis is largely clinical although biopsies are typically taken.
Patients with suspected metastasis may require staging via CT, MRI or PET imaging. Staging is done using the TNM staging system (tumour, node and metastasis).
Management
- Excision: This is the typical first-line treatment. The margins left will vary depending on how high risk the lesion is, but it typically ranges from 4mm-10mm.
- Mohs Micrographic Surgery: This is where a lesion is excised layer-by-layer, and each layer is examined microscopically. Excision continues until tumour is no longer visible on microscopy. This can be useful for sites where you are trying to conserve as much tissue as possible e.g. facial lesions.
- Curettage/Cautery: This is where a curette is used to excise tumour tissue (usually involves scraping away at the tumour). The base of the tumour is then destroyed typically using cautery. This is usually considered for smaller, lower-risk lesions.
- Radiotherapy: Usually offered either as an adjuvant for higher risk SCCs or offered in patients not suitable for surgery
Tumours can be considered high risk for various reasons. Some of the features that make a tumour high risk include
- SCC from the ear
- Tumour diameter >20mm
- Associated immunosuppression of the patient
References
https://www.skincancer.org/skin-cancer-information/squamous-cell-carcinoma/scc-warning-signs-and-images/
https://www.uhb.nhs.uk/Downloads/pdf/CancerPbSquamousCellCarcinomaSkin.pdf
Davidson’s Principles and Practice of Medicine
https://patient.info/doctor/squamous-cell-carcinoma-of-skin
https://dermnetnz.org/topics/keratoacanthoma
https://onlinelibrary.wiley.com/doi/full/10.1111/bjd.19621
