Squamous cell carcinoma (SCC), also known as squamous cell epithelioma, is a malignant tumor originating from the keratinocytes of the epidermis. It is the second most common type of skin cancer. The earlier SCC is diagnosed, the easier it is to treat. Early diagnosis leads to cure in the majority of cases.
SCC is found both on the skin and on mucous membranes, where it represents the most common type of cancer. It develops either de novo (from the beginning),
or more commonly, on pre-existing cutaneous or mucosal epithelial precancerous lesions.
Squamous cell carcinoma usually presents as an ulcerated nodule with an irregular, reddish, exophytic surface that is slightly painful and easily bleeds. The base of the tumor is indurated due to infiltration, and this “board-like” hardness often extends beyond the visible margins of the tumor. The floor appears dirty and contains either easily bleeding papillomatous outgrowths or, more commonly, white spots corresponding to areas of keratinization. Often, the ulceration is covered by a crust. In other cases, SCC may present as a raised exophytic mass without a tendency to ulcerate.
The incidence varies across different geographic regions. The highest rates are observed in Australia, with an annual incidence of 250 cases per 100,000 inhabitants. In the United States, the annual incidence is 146 cases per 100,000 white men, 100 per 100,000 white women, and 3 per 100,000 individuals of Black ethnicity.
These data highlight the significant protective role of melanin in the epidermal keratinocytes against the harmful effects of ultraviolet radiation. The incidence of squamous cell carcinoma increases with age, due to the cumulative effect of UV exposure.
Ultraviolet radiation plays a prominent role in the development of squamous cell carcinoma, with its effects being cumulative. Additionally, skin pigmentation is a significant factor, as individuals with fair skin phototypes are more susceptible to skin cancer.
Other factors with carcinogenic potential for the skin include:
- Human papillomavirus (HPV) types (6, 11, 16, etc.)
- Ionizing radiation
- Infrared radiation
- Photochemotherapy (PUVA)
- Arsenic
- Polycyclic aromatic hydrocarbons
- Therapeutic use of nitrogen mustard (in cutaneous lymphomas)
- Chronic non-healing ulcers
- Scars and chronic inflammatory conditions
- Immunosuppression (e.g., HIV infection, organ transplant recipients)
- Heredity
- Genodermatoses
- Precancerous lesions
- Chronic dermatoses
- Smoking (especially in cases of lip squamous cell carcinoma)
a. Hyperkeratoses, such as actinic keratoses, solar keratoses, cutaneous horn, and arsenical keratosis
b. Porokeratoses (Mibelli type and disseminated superficial actinic porokeratosis)
c. Epidermal sebaceous nevus of Jadassohn
d. Bowenoid papulosis
e. Actinic cheilitis
f. Leukoplakia
Non-precancerous dermatoses with a potential risk of developing squamous cell carcinoma include discoid lupus erythematosus, chronic non-healing ulcers, erosive lichen planus of the mucous membranes, lichen sclerosus et atrophicus, deep fungal infections, hidradenitis suppurativa, tertiary syphilis, epidermolysis bullosa, lymphogranuloma venereum, granuloma inguinale, and others.
The clinical types of squamous cell carcinoma include:
1. In situ forms: Bowen’s disease, Paget’s disease, Queyrat’s erythroplasia, and leukoplakia
2. De novo SCC
3. SCC arising from precancerous lesions
4. SCC of the extremities
5. SCC of the lower lip
6. SCC of the oral cavity
7. SCC of the genitalia: vulva, penis, scrotum
8. Verrucous carcinoma (a rarer form of squamous cell carcinoma).
a. Surgical excision with safety margins of 0.5–1 cm, when feasible, followed by histopathological examination
b. MOHS micrographic surgery (the ideal method of removal)
c. In cases of lymph node involvement, MOHS surgery combined with lymph node dissection is recommended
d. In the presence of metastases, initial chemotherapy is advised, followed by surgical excision and then radiotherapy.
Individuals considered to be at higher risk for developing squamous cell carcinoma include:
- Older adults
- Individuals with a hereditary predisposition
- People with fair skin and light-colored eyes who burn easily in the sun and do not tan
- Individuals with blond or red hair
- Males
- People with occupational or recreational outdoor exposure and chronic ultraviolet radiation exposure
- Individuals exposed to ionizing radiation
- People with long-term exposure to substances such as arsenic
- Patients with HPV infection
- Immunosuppressed individuals (e.g., those with HIV)
The removal of a squamous cell carcinoma does not eliminate the possibility of developing a new cancerous lesion in the same or another area of the body. For this reason, follow-up examinations with a dermatologist every six months are recommended. In the event of any clinical change in a pre-existing lesion or the appearance of a new one, it is important to inform your dermatologist immediately.