Polydactylous Squamous Cell Carcinoma of the Nail Unit: A Structured Review of the Literature

Update on Squamous Cell Carcinoma of the Nail Unit: An Human Papillomavirus-Associated Condition

Background

Squamous cell carcinoma (SCC) and SCC in situ (Bowen's disease) are the most common malignancies of the nail unit. They are frequently seen in men over 50 and most commonly affect the fingers. The role of high-risk human papillomavirus (HPV) infection has been identified as a key contributor to the development of nail unit SCC.

Summary

In this review, we aimed to summarize the current state of our understanding of how HPV contributes to nail unit SCC, the role of genitodigital transmission of HPV, and the clinical features of HPV-associated nail unit SCC. We also review current advances in the treatment of nail unit SCC, with a focus on the potential role of HPV vaccination in the treatment and prevention of nail unit SCC.

Key Messages

Nail unit SCC should be recognized as an HPV-associated disease. HPV vaccination may represent a non-surgical modality for the management of these challenging malignancies in the appropriate clinical setting.

Nail disorders to be kept in mind

Recognizing and diagnosing the most common nail diseases is essential, to be able to guide patients and provide appropriate treatment. However, uncommon nail disorders should not be neglected, in order to avoid inadequate treatment and above all to ensure that no severe underlying disorder, with severe prognosis, is overlooked.

Squamous Cell Carcinoma in Situ of the Nail Unit: Current Evidence and Recommendations for Patient Centered Treatment

Squamous cell carcinoma in situ of the hand and nail is an infrequent tumor but represents the majority of hand and nail malignancies. While the conventional treatments of invasive nail unit squamous cell carcinoma include Mohs micrographic surgery, wide local excision, or distal digit amputation, no standardized management paradigm for in situ disease exists and the necessity of surgical options is debated. This review aims to discuss the most commonly reported treatment methods and critically assess relevant management considerations in order to facilitate appropriate treatment decisions for nail unit SCCis across dermatologic practice settings. Assessment of the current literature reveals insufficient evidence to determine a standardized treatment for nail unit squamous cell carcinoma in situ. Rather, management is greatly impacted by multiple factors including the presence of subungual involvement, surgical candidacy, importance of curative treatment, and patient preferences regarding cosmesis and function versus cure. When cure is desired, Mohs micrographic surgery is the treatment of choice in most cases. In the setting of desired curative intent, but poor surgical candidacy, radiotherapy may be effective and provide a reasonable chance of functional and cosmetic preservation. Other methods including photodynamic therapy, electrodesiccation and curettage, cryotherapy, and intralesional chemotherapeutics may be appropriate in specific circumstances, but are generally limited by lack of evidence or impracticalities. Lastly, observation with palliation may be appropriate when considering exceedingly rare disease-related mortality.