Cutaneous squamous cell carcinoma - Hair and Scalp
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Synopsis
Skin phototype is the most important factor related to developing this cancer, as individuals with lighter skin types are at about 80 times higher risk than darkly pigmented individuals. In individuals with darker skin phototypes, 30%-40% of SCCs develop within scars and chronic nonhealing ulcers (compared to 2% developing within such areas in people with lighter skin phototypes). SCC is the most common and second most common skin cancer in Black individuals and individuals of Hispanic descent, respectively.
A variety of other risk factors increase the likelihood of developing SCC. These include ultraviolet (UV) exposure, solid organ transplantation, ionizing radiation exposure, cigarette smoking, human papillomavirus (HPV), chemical exposure (ie, arsenic, mineral oil, coal tar, soot, mechlorethamine, polychlorinated biphenyls, and psoralen plus UVA treatment), freckling, red hair, immunosuppression such as HIV disease / AIDS, and chronic nonhealing wounds. Dermatoses associated with a risk of SCC include discoid lupus erythematosus, lichen planus (ie, erosive, hypertrophic), and lichen sclerosus. A variety of genetic syndromes have also been associated with SCC. These include xeroderma pigmentosum, oculocutaneous albinism, epidermodysplasia verruciformis, dystrophic epidermolysis bullosa (recessive), Ferguson-Smith syndrome, and possibly Muir-Torre syndrome. Medications can also lead to the development of SCCs. Immunosuppressives, such as systemic immunomodulators or biologics, increase the risk of SCC, and the risk is proportional to length of therapy. Other implicated medications include voriconazole, thiopurine in patients with irritable bowel disease, BRAFV600 inhibitors such as vemurafenib and dabrafenib, and photosensitizing antihypertensive drugs such as alpha‐2 receptor agonists and diuretics.
Although SCC can arise on any skin surface including mucosa, the most common areas of involvement are sun-exposed areas such as the head, neck, arms, and hands. The clinical presentation is highly variable among different demographic groups and tumor subtypes. Lesions may grow slowly or evolve rapidly.
The rate of metastasis is approximately 4%. The most common site of metastasis is the regional lymph node, but distal metastasis has been reported. Risk of metastasis is higher in immunosuppressed individuals, particularly solid organ transplant recipients, in primary lip lesions, and in non-UV-related SCCs.
Some features classify SCC as having a high risk of recurrence. These include aggressive histopathologic types (acantholytic, adenosquamous, carcinosarcomatous), depth more than 2 mm, size more than 2 cm, poorly defined borders, location at a site of prior radiation / burn or chronic inflammatory process, specific anatomic location (ie, tongue, vulva, penis), history of immunosuppression, moderate or poor differentiation on pathology, desmoplasia, and perineural or angiolymphatic invasion. These features may lead to selection of a treatment option with lower recurrence rates. Mohs micrographic surgery (MMS) has been shown to have less recurrence than standard surgical excision.
Various staging systems exist, although none is universally accepted. See Work Group. Guidelines of care for the management of cutaneous squamous cell carcinoma. J Am Acad Dermatol. 2018 Mar;78(3):560-578.
Related topics: oral squamous cell carcinoma, squamous cell carcinoma in situ
Codes
ICD10CM:C44.92 – Squamous cell carcinoma of skin, unspecified
SNOMEDCT:
402815007 – Squamous cell carcinoma
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Diagnostic Pearls
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Differential Diagnosis & Pitfalls
- Hypertrophic actinic keratosis
- Bowen disease
- Basal cell carcinoma
- Verruca vulgaris
- Condyloma acuminatum
- Keratoacanthoma
- Eccrine poroma
- Lobular capillary hemangioma (pyogenic granuloma)
- Amelanotic melanoma
- Sporotrichosis
- Mycobacterium marinum infection
- Nummular dermatitis
- Atypical fibroxanthoma
- Merkel cell carcinoma
- Irritated seborrheic keratosis
- Chronic draining or ulcerative lesions
- Discoid lupus erythematosus
- Lichen planus
- Lichen sclerosus
- Granuloma inguinale
- Lymphogranuloma venereum
- Syphilis
- Prurigo nodularis
- Bowenoid papulosis
- Lichen planus-like keratosis (see, eg, lichenoid drug eruption)
- Adnexal carcinomas
- Lymphoma cutis, especially anaplastic large cell lymphoma
- Lymphomatoid papulosis
- Dermatofibrosarcoma protuberans
- Leiomyosarcoma
- Extramammary Paget disease
- Epithelioid sarcoma
- Psoriasis
- Lichen simplex chronicus
- Basosquamous carcinoma
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Therapy
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Drug Reaction Data
Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.Subscription Required
References
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Last Reviewed:09/26/2018
Last Updated:04/05/2021
Last Updated:04/05/2021
Cutaneous squamous cell carcinoma - Hair and Scalp
See also in: Overview,Anogenital,Nail and Distal Digit