Getting a head up on cutaneous scalp malignancies

By Warren R. Heymann, MD, FAAD
May 7, 2025
Vol. 7, No. 18

I’m confident that your alopecic patients with a suspected keratinocyte carcinoma or melanoma of the scalp jokingly ask you to be careful with your biopsy procedure so they do not lose any more hair. While patients and dermatologists correctly assume that scalp malignancies are more frequent on the scalp of alopecic patients because of increased ultraviolet (UV) exposure, what other factors are at play?

It is well-recognized that the incidence of skin cancer can be reduced by UV minimization strategies such as seeking shade, avoiding the midday sun, wearing hats, clothing, sunglasses, and sunscreens. Parisi et al. calculated an ultraviolet protection factor (UPF) that ranged from approximately 5 to 17 in full sun, with the UPF increasing with higher solar zenith angles. Interestingly, the UPF provided by the shorter hair was generally higher by a range of 2–5 than that provided by the longer hair — this was attributed to more parting of the subjects with long hair, which allowed for a greater surface area for UV exposure. (1)

The level of protection offered by hair according to hair density, thickness, and color using the spectral transmittance and corrected for relative erythema effectiveness was analyzed by de Gálvez et al. They demonstrated that hair provides a barrier against both UVB and UVA radiation; the protection is significantly greater with increased hair density, thickness, and the presence of melanin. Higher levels of light transmittance in white hair compared to colored hair (brown, red, or blond) were observed. (2) Although this commentary focuses on the scalp, Marro et al. studied eyelashes’ filtering effect for various light incidence angles, diameter, and cilia density. They found that eyelashes reduce UV light received by the cornea by about 12–14%, with maximum values of 24%. (3)

According to Lousada et al, “HF [hair follicle] epithelium differs from the epidermal barrier in that it provides a moist, less acidic, and relatively ultraviolet light-protected environment, part of which is immune-privileged, thus facilitating microbial survival… An increased abundance of both Malassezia restricta and M. globose has recently been reported in alopecic vertex areas compared with occipital skin and healthy controls. Further, recent 16S rRNA sequencing data have suggested that miniaturized vertex HFs in patients with androgenetic alopecia harbour increased P. acnes populations. It now needs to be elucidated whether these HF microbiome alterations are functionally relevant, e.g. for the discrete perifollicular inflammation associated with HF miniaturization in androgenetic alopecia and for the miniaturization process as such.” (4) Thus, the hair follicle microbiome could be indirectly involved in carcinogenesis.

Immunosenescence is associated with an increased risk of malignancy. Lian et al assert, “The role of immunosenescence in tumors is sophisticated: the many factors involved include cAMP, glucose competition, and oncogenic stress in the tumor microenvironment, which can induce the senescence of T cells, macrophages, natural killer cells, and dendritic cells. Accordingly, these senescent immune cells could also affect tumor progression.” (5)

Kaplan et al. hypothesize that hair protects against the development of skin cancer, by serving as a physical shield, and providing continuous IL-17 biased immunosurveillance. IRF4 is a transcription factor present in hair that plays a role in pigmentation and IL-17 mediated inflammation. “Loss of hair allows release from immunosurveillance, resulting in expansion of neoplastic cells towards skin cancer. Both hair follicles and metabolic changes in stroma allow permissiveness for tumor promotion.” With the loss of IL-17, the stroma becomes elevated in TGF-beta and low in Sirt3 [a mitochondrial deacetylase which stimulates mitochondrial biogenesis], proving a permissive environment for tumor progression. (6)

Dermatologists have experienced a surge of patient interest in treating androgenetic alopecia since the popularization of low-dose oral minoxidil. (7) In discussing the pros and cons of a pharmacological approach to alopecia, rarely (if ever) has the issue of cancer prevention been taken into consideration. Perhaps it should. At the very least, we should remind patients that there is more to a luxurious mane than appearance.

Point to Remember: Cutaneous scalp malignancies are common in patients with alopecia. Research suggests hair prevents carcinogenesis by physically blocking ultraviolet light and other mechanisms.

Our expert’s viewpoint

Jack L. Arbiser, MD, PhD, FAAD
Thomas J. Lawley Professor of Dermatology, Emeritus
Department of Dermatology
Emory University School of Medicine
Winship Cancer Institute
Atlanta Veterans Administration Health Center

Two of the most common reasons to visit a dermatologist are the scalp disorders hair loss and actinic keratoses. I speak for many when I find treatment of actinic keratoses more rewarding than hair loss. Many cases of hair loss are apparent to the patient but not to the dermatologist, as we do not have a baseline, but have only the word of the patient to substantiate it. Our therapies lag in terms of treatment, with finding a distinct cause, i.e. alopecia areata, seborrheic dermatitis, traction alopecia as a first priority. Assuming we don't find any distinct abnormalities, hair loss is usually characterized as “pattern alopecia.” Rarely, metabolic disorders, i.e. thyroid and iron dysfunction are discovered. Treatment lags behind, with oral minoxidil (an old drug) our latest addition to our limited armamentarium.

On the other hand, actinic keratoses are easy to treat and quantify response. Response is immediate (cryotherapy and Efudex) and can be both documented by the patient and photography. We are highly effective in destroying actinic keratoses, making this a satisfying diagnosis for dermatologists.

Hair loss and actinic keratoses may be linked. In our review of carcinogenesis of the scalp, and the expert commentary by Dr. Heymann, we discuss the phenomenon that the scalp is supposedly a sun-protected area during youth, but skin cancers of the scalp are nearly as common as areas that get constant sun exposure since birth, i.e. the nose, cheeks, neck, etc. This suggests that hair is not a particularly good UV barrier, and the studies cited by Dr. Heymann demonstrate that a lot of UV radiation gets through the hair. We discuss the possibility that the presence of hair results in tonic IL-17 production, which inhibits carcinogenesis, and loss of hair thus promotes loss of Il-17, and allows development of skin cancer. There are major implications to this. First, physical barriers, such as hats, may prevent skin cancer on the scalp. Second, measures to prevent alopecia may also be beneficial in preventing skin cancer on the scalp. Thus, it is time to “lean in” to alopecia, and treatment of alopecia may not be just for vanity, but may prevent skin cancer as well.

1. Parisi AV, Smith D, Schouten P, Turnbull DJ. Solar ultraviolet protection provided by human head hair. Photochem Photobiol. 2009 Jan-Feb;85(1):250-4. doi: 10.1111/j.1751-1097.2008.00428.x. Epub 2008 Aug 27. PMID: 18764896.

2. de Gálvez MV, Aguilera J, Bernabó JL, Sánchez-Roldán C, Herrera-Ceballos E. Human Hair as a Natural Sun Protection Agent: A Quantitative Study. Photochem Photobiol. 2015 Jul-Aug;91(4):966-70. doi: 10.1111/php.12433. Epub 2015 Mar 12. PMID: 25682789.

3. Marro M, Moccozet L, Vernez D. Modeling the protective role of human eyelashes against ultraviolet light exposure. Comput Biol Med. 2022 Feb;141:105135. doi: 10.1016/j.compbiomed.2021.105135. Epub 2021 Dec 18. PMID: 34959113.

4. Lousada MB, Lachnit T, Edelkamp J, Rouillé T, Ajdic D, Uchida Y, Di Nardo A, Bosch TCG, Paus R. Exploring the human hair follicle microbiome. Br J Dermatol. 2021 May;184(5):802-815. doi: 10.1111/bjd.19461. Epub 2021 Feb 18. PMID: 32762039.

5. Lian J, Yue Y, Yu W, Zhang Y. Immunosenescence: a key player in cancer development. J Hematol Oncol. 2020 Nov 10;13(1):151. doi: 10.1186/s13045-020-00986-z. PMID: 33168037; PMCID: PMC7653700.

6. Kaplan, B.; von Dannecker, R.; Arbiser, J. Carcinogenesis of the Human Scalp. An Immunometabolic Centered View. Preprints 2024, 2024090450. https://doi.org/10.20944/preprints202409.0450.v1

7. Heymann WR. Coming full circle (almost): Low dose oral minoxidil for alopecia. J Am Acad Dermatol. 2021 Mar;84(3):613-614. doi: 10.1016/j.jaad.2020.12.053. Epub 2021 Jan 6. PMID: 33421481.

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