Nonmelanoma Skin Cancers: Embryologically Relevant Sites and UV Exposure

Abstract

Background: Traditionally, nonmelanoma skin cancers (NMSCs) are considered mainly UV-related malignancies. Nevertheless, a strong correlation between the embryologically relevant sites (ERS) of the head and neck and the preferential sites of onset of basal cell carcinomas (BCCs) has long been supposed and demonstrated. The aim of this research was the investigation of the potential correlation between the ERS of the head and neck and the sites of tumor onset in all of the NMSCs.

Methods: The distribution of 1165 NMSC was correlated with the ERS of the head and neck using the universally accepted anatomical diagrams featuring the congenital head and neck clefts and an original anatomical diagram showing the most credited sites of the embryonic fusion planes of the auricle.

Results: In our sample, both BCC and SSC display an increased likelihood of onset in the ERS of the head and neck. A proportion of 93.10% BCCs was distributed within ERS, while 6.90% derived from non-embryologically relevant sites (P < 0.001). A proportion of 69.70% SCCs was distributed within ERS, while 30.30% derived from non-embryologically relevant sites (P < 0.001). The probability of tumors within ERS was significantly higher for BCC versus SCC (P < 0.001), with BCCs having a 5-fold increase in the probability of occurring in ERS compared to SCCs (P < 0.001).

Conclusions: The ERS might host areas of cellular instability yielding to the development of an NMSC. The environmental UV exposure plays a relatively main role versus dysontogenic factors in the pathogenesis of SCC.

Fig. 1.

The original Tessier anatomical diagram of craniofacial clefts: localization on (A) the soft tissues and (B) skeleton. The dotted lines are either uncertain localizations or uncertain clefts. Reprinted with permission from Elsevier: Tessier P. Anatomical classification facial, craniofacial and latero-facial clefts. J Maxillofac Surg. 1976;4:69–92.

Fig. 2.

Diagram featuring the hairline indicators representing the superior and lateral extensions of the Tessier original craniofacial cleft classification. Reprinted with permission from Wolters Kluwer Health: Moore MH, David DJ, Cooter RD. Hairline indicators of craniofacial clefts. Plast Reconstr Surg. 1988;82:589–593 ©1988 Wolters Kluwer Health.

Fig. 3.

Anatomical original diagram featuring the typical sites of congenital clefts, fistulas, and cysts of the neck: the laterocervical line (L.L.) and the anterior neck midline (Tessier cleft number 30). Reprinted with permission from Wolters Kluwer Health: Nicoletti G, Brenta F, Malovini A, Jaber O, Faga A. Sites of basal cell carcinomas and head and neck congenital clefts: topographic correlation. Plast Reconstr Surg. 2014: 2(6): e164. ©2014. The Author(s).

Fig. 4.

Original anatomical diagram showing the sites of the embryonic fusion planes of the auricle according to Streeter, Wood Jones, Park, Porter, and Minoux. The hyoid-mandibular fusion plane (HM-FP) is featured in red, and the free ear fold-hyoid fusion plane (FEFH-FP) in blue. Reprinted with permission from SAGE Publications Ltd.: Nicoletti G, Tresoldi MM, Malovini A, Prigent S, Faga A. Correlation between the sites of onset of basal cell carcinoma and the embryonic fusion planes in the auricle. Clinical Medicine Insights: Oncology. 12(1): 1–5, 2018.

Fig. 5.

Tumors distribution by ERS.

Fig. 6.

Tumors distribution by non-embryologically relevant sites.

Fig. 7.

Distribution of UV exposure on a coated manikin with a chemical ultraviolet dosimeter. Lighter-colored areas indicate less sun exposure. Reprinted with permission from Elsevier from: Urbach F. Geographic pathology of skin cancer. In: Biologic effects of ultraviolet radiation (with emphasis on skin). Oxford Pergamon Press ©1969: 643.