Squamous cell carcinoma of the skin is a common cancer to be aware of when treating patients in a wound clinic due to its physical appearance and its likelihood to mask itself within healing burns and scar tissue.  It occurs when keratinocytes, or cells of the epidermis, proliferate uncontrollably forming a mass.  Although not as likely, it is possible for cutaneous squamous cell cancer to metastasize to other locations in the body and wreak havoc making diagnosis and treatment imperative especially in immunocompromised and comorbid patients.

Clinical presentation – There are two forms of cutaneous squamous cell carcinoma: the localized form, or “in situ”, and the invasive form (ISCC). The invasive form can either be composed of differentiated cells or undifferentiated cells.  SCC is most likely to occur in males over the age of 55 in the United States. Those with fair skin are more susceptible, and areas with more sun exposure have a higher incidence rate.

The most benign case is “in situ” and usually presents as a sharply demarcated, scaling or hyperkeratotic macule, papule or plaque. Lesions are commonly either pink or red and can form a crust. Squamous cell carcinoma in situ as a result of infection from HPV can be tan, brown or black and occur in the anogenital region.

Invasive squamous cell carcinoma that is comprised of differentiated cells presents as an indurated papule, plaque or nodule with keratinization and is firm to palpation. It may be scaling, crusted or ulcerated and is usually raised. It is located on areas exposed to UV light like the face (including the lips), tips of the ears, scalp, dorsa of the hands and forearms. Interestingly, it is also known to show up on the shins of females.

Invasive squamous cell carcinoma made of undifferentiated cells, in contrast, does not show signs of keratinization and appears more like a granuloma or normal flesh and is soft on palpation. This form is more likely to be irregularly shaped, appear red, and have a necrotic base. It may be erosive, ulcerated, or easily damaged with force of palpation causing it to bleed. It is found on the trunk, lower extremities and only rarely on the face. However, undifferentiated ISCC is common to the anogenital region where it can be seen alone or in multiples.

Etiology – The two most likely precursors increasing the risk of developing squamous cell carcinoma of the skin is exposure to ultraviolet radiation and the human papilloma virus. UV light is especially harmful in people with skin types I and II which are the most fair-colored and susceptible. HPV infects skin cells and increases the likelihood of the cell cycle becoming unregulated. Other risk factors are methotrexate treatment, being immunosuppressed by HIV or transplant, having burn scars or chronic ulcers, and radiation treatment affecting the skin.  Certain chemicals have also been linked to ISCC like arsenic exposure.

Diagnosis – Definitive diagnosis can only be made through biopsy.  If the lesion is nodular, it is excised via shave biopsy.  If the lesion is a macule or patch, it is excised via punch biopsy.

Differential – Any nodule that is constant and appears on sun-exposed skin, in burn wounds or in the anogenital region must be considered squamous cell carcinoma until proven otherwise.  Localized squamous cell carcinoma can present like psoriasis, nummular eczema, Paget’s disease, or basal cell carcinoma.

Treatment – Squamous cell carcinoma in situ of the skin can be treated with either 5-FU topical chemotherapy, imiquimod or cryotherapy. Invasive forms are removed entirely via surgery to ensure clear margins and are then closed either primarily or with skin grafts. Radiotherapy is only considered if surgery is not possible.

Prognosis – The five year survival rate is greater than 90%.  Patients diagnosed with squamous cell carcinoma should be followed closely by a dermatologist every 3-6 months for the first two years to monitor for recurrence.

Contributing author Mary Katherine Brewer, MS3 Campbell University College of Osteopathic Medicine

References

Chautier, T., Aasi, S., & Corona, R. (2014, November 19). Treatment and prognosis of cutaneous squamous cell carcinoma (R. Stern & J. Robinson, Eds.). Retrieved January 5, 2016, from http://www.uptodate.com.proxy.campbell.edu/contents/treatment-and-prognosis-of-cutaneous-squamous-cell-carcinoma?source=machineLearning&search=squamous cell carcinoma skin&selectedTitle=1~88§ionRank=1&anchor=H26#H26

Fitzpatrick, T., & Johnson, R. (2001). Precancerous Lesions and Cutaneous Carcinomas. In Color atlas and synopsis of clinical dermatology: Common and serious diseases (4th ed., pp. 255-260). New York: McGraw-Hill, Medical Pub. Division.