Unusual Cutaneous Squamous Cell Involving Distal Extremities

Abstract and Introduction

Abstract

Introduction: cSCC is the second most common cutaneous malignancy worldwide behind basal cell carcinoma. Typically, SCC is diagnosed early before it infiltrates local subcutaneous tissue or metastasizes. However, unusual presentations are possible and can lead to delayed treatment and possibly worse outcomes.

Materials and Methods: All patients were White of non-Hispanic or Latino decent. Three-quarters of the cases were male, and a quarter female. The age range was 45 to 78 years. The documented sizes of lesions ranged from 6 cm to 10 cm in diameter. Three of the cases were initially diagnosed as nonhealing wounds, and one was diagnosed as cellulitis.

Results: The authors observed that SCC can present unusually by mimicking nonhealing infected ulcers or skin infections such as cellulitis. Over 18 months, the authors' practice recorded 4 cases of cSCC that were initially treated as persistent infections, which potentially lead to worse outcomes.

Conclusion: These cases provide patterns and clues to potentially expedite the diagnosis and treatment of cSCC. Any skin lesion thought to be infectious but not responding to treatment should undergo tissue sampling.

Introduction

cSCC originates from the keratinocyte in the epidermis, where it may spread superficially or begin to infiltrate the dermis and beyond. Classically, cSCC appears as a firm "keratotic" or rough papule or plaque. It can sometimes ulcerate and appear as a nonhealing lesion that is easily friable and prone to bleeding.^[1] Roughly 20% of all skin cancers in the United States are cSCCs, and death from cSCC can occur in a minority of cases. Lifetime incidence of cSCC in the United States ranges from 14% to 20% in the non-Hispanic White population.^[2,3] Risk factors for cSCC include but are not limited to Fitzpatrick skin type I-III, advanced age, being genetically male, UV exposure, human papillomavirus, and immunosuppression. A meta-analysis of 36 studies showed that Breslow thickness greater than 2 mm, perineural involvement, invasion beyond subcutaneous fat, poor differentiation, and location on the temple were risk factors for recurrence, metastasis, and disease-specific death.^[4] Once cSCC is diagnosed by skin biopsy, standard excision is generally the treatment of choice, while Mohs micrographic surgery is often the treatment of choice for cancers in areas where excess tissue is limited. In instances where Mohs surgery is not practical, other treatments may be used, such as radiation, topical treatments (eg, 5-fluororacil), and immunotherapy (eg, PD-1 inhibitors).^[5] In order to facilitate treatment, it is best to diagnose cSCC early. Occasionally, however, this can be difficult, as the authors illustrate in the following cases.