Squamous Cell Carcinoma
In keeping with our theme for summer, we are moving forward with skin cancers.
For a refresher on basal cell carcinoma, please review our previous article here.
We will now be covering the second most common type of skin cancer as the weather warms: squamous cell carcinoma.
Squamous cell carcinoma is a form of skin cancer that arises from a malignancy of the epidermal keratinocytes. Due to factors such as increased sun exposure, lack of sunscreen, and the aging population, squamous cell carcinoma (SCC) is a fast rising skin cancer that accounts for up to 20% of non-melanoma skin cancer and for up to 200,000 new cases/year. (Gonzalez and Goodheart, 2016).
Risk factors for Squamous Cell Carcinoma
The risk factors for SCC are numerous, but are predominantly related to:
- Increased age
- Increased total UV light exposure
- Fair skinned individuals
- Lack of sunscreen use.
Individuals with red hair, family or personal history of SCC, and European descent are also at risk.
Other influential risk factors include immunosuppression, smoking, history of actinic keratosis, history of radiation, and tanning bed use. In one study, tanning bed use at any point in the individual’s lifetime presented a 67% increased risk of SCC (Lim and Asgari, 2019).
The pathophysiology of the development of SCC is multifactorial and for the most part, goes beyond the scope of this article. We will, however give a brief summary of the key components.
The initial step is that UV radiation (from the sun) damages the DNA in skin cells, which alters the tumor suppressor gene. Skin cells will then grow uncontrollably, and eventually, additional mutations lead to squamous cell dysplasia. Additional consecutive exposure can increase the risk for development of SCC.
The suspicion for an abnormal skin lesion, as discussed in our article on basal cell carcinoma, may come directly from the patient or may be found as part of the primary care routine examination. Many times in my practice, patients will make acute visits for non-healing lesions of concern, or I may find an abnormal lesion on examination.
The lesions associated with SCC, or that have the potential to become an SCC, are commonly found on the face, back, forearms, hands, bald areas of the scalp, legs, and the chest. It is important for the practitioner to examine each area thoroughly, even if the patient does not note a concern.
What do we look for?
SCCs tend to be slow growing, hyperkeratotic papules, nodules, or plaques.
As discussed above, often times SCCs may be asymptomatic to the patient.
If symptoms occur, the patient may complain of bleeding, pain, or tenderness. The degree of crusting, expansion, scaling is variable and the color may be red, tan, dark, or pearly.
When referring to dermatology, or if discussing the case with another clinician, there are further distinctions that can be made, rather than simply indicating “the patient may have an SCC”.
Bowen disease is better known as SCC in situ, and this is a solitary, single lesion, that can be easily mistaken for a psoriatic plaque. It is a favorite among PACKRAT and PANCE examinations, in my experience.
A cutaneous horn may also manifest with SCC. A cutaneous horn is a fingernail like projection that is also produced by the SCC (Gonzalez and Goodheart 2016).
A common mistake among providers is that we don't do thorough exams, and sometimes forget to check areas such as the hair or the nails. A subungal SCC is a lesion that is under the nail-plate, which can sometimes be mistaken for a wart.
Once the diagnosis is suspected, via the abnormal skin examination, the provider should be cautious to monitor for other lesions. It is common for us to identify a skin lesion and stop our focus there.
If there is concern for a deep seating, metastatic lesion, the clinician should also form a lymphatic exam, looking for lymphadenopathy in the region.
If a a facial lesion is found, then the clinician should ensure to check for neck lymphadenopathy as well. If it is detected, CT scan, MRI, or PET scan can stage disease, as SCCs do have the potential to metastasize.
Biopsy of Squamous Cell
Any suspicious lesion should be biopsied. The decision to biopsy can also be complicated by what type of biopsy is needed: shave, punch, excisional, or incisional.
For providers not trained on skin biopsies, I suggest a referral to dermatology for evaluation. Lesions that are present on the face or in areas of cosmetic consideration may be sent to dermatology or plastic surgery.
It is important to note that actinic keratosis is a precursor to SCC and should be treated as such. These types of lesions may be excised in the hopes of preventing subsequent development of an SCC, or may be monitored for a period of time.
The treatment of SCCs is vastly surgical.
The primary treatment is total excision which must be accounted for with tumor margins. Histopathology can help the clinician identify whether initial excision had clean borders or whether subsequent procedure is needed.
Electrocautery and curettage is also a potential option and is used commonly for actinic keratosis. This is used for lower risk SCCs as well (Gonzalez and Goodheart, 2016). Mohs surgery is used for sensitive areas, such as the face and also has the highest cure rate.
In addition to the role of surgical treatment, another potential option is immunotherapy with imiquimod (aldara) and 5-fluorouracil. Patients with signs and symptoms of significant metastasis should be referred to a surgical oncologist. Patients undergoing excisional removal of an SCC should have routine skin exams to screen for further recurrence and/or new lesions.
We have discussed the prevention of skin cancers with our article on basal cell carcinoma previously, but it is worth re-mentioning. If you are reading this while poolside, celebrating the end of your didactic year without any sunscreen on, shame on you!
Broader spectrum sunscreens between 30 to 50 SPF are key. It should be re-applied every few hours, especially if sweating or getting wet.
Avoiding tanning beds is one of the key features as well and wearing long sleeves, hats and pants during peak sun hours is crucial as well.
We are moving forward in our important discussion of skin cancers, and at this point have covered both BCCs and SCCs.
As the summer continues to roll on, can you guess what we will cover in sunny July?
- Gonzalez, M.E and H.P. Goodheart (2016). Squamous cell carcinoma, cutaneous. The 5 Minute Clinical Consult.
- Lim, J.L and Asgari, M (2019). Epidemiology and Risk Factors for cutaneous Squamous Cell Carcinoma. UpToDate, date of access 9 June 2019.