Chapter 178: Squamous Cell Carcinoma

PATIENT STORY

A 75-year-old man presents with a 2.6-cm enlarging inflamed tumor on the right cheek (Figure 178-1). He has a history of many actinic keratoses and grew up with significant sun exposure. Scoop shave biopsy is consistent with squamous cell carcinoma (SCC), and he undergoes Mohs surgery. Figure 178-2 shows a shave biopsy of a smaller lesion on the scalp. Following excision, he follows up regularly for skin exams in order to detect any skin cancers or recurrence at an early stage.

INTRODUCTION

Cutaneous SCC is the second most common cancer in humans and arises most often as a result of cumulative sun damage. Incidence of cutaneous SCC (cSCC) in U.S. Medicare patients has been shown to have reached an incidence equal to that of basal cell carcinoma.¹ Although the mortality is declining, incidence is increasing in all populations, making this cancer a common and significant burden on patients.

EPIDEMIOLOGY

• Mortality from SCC has been observed as 0.29 per 100,000 population.²

• Metastasis from SCC occurs in 2% to 9.9% of cases.³

• The incidence is increasing in all age groups and populations at a rate of 3% to 10%.³

• In the United States, at least 200,000 to 400,000 new cases of cutaneous SCC are expected per year. Disease-related death occurs in more than 3000 people yearly.^4,5

• SCC is the second most common skin cancer and accounts for at least 25% of nonmelanoma skin cancers.⁴

• SCC is the most common skin cancer in Hispanic, black, and Asian patients.⁶

PATHOPHYSIOLOGY

SCC is a malignant tumor of keratinocytes. Most SCCs arise from precursor lesions called actinic keratoses. SCCs usually spread by local extension but are capable of regional lymph node metastasis and distant metastasis. Human papillomavirus (HPV)-related lesions may be found on the penis, labia, and perianal mucosa, or in the periungual region or elsewhere associated with immunosuppression.⁷

SCCs that metastasize most often start on mucosal surfaces and sites of chronic inflammation.

RISK FACTORS

• Long-term cumulative UV exposure is the greatest risk factor.

• Childhood sunburns.

• Occupational exposure.

• Other UV exposure including psoralen and UVA (PUVA) therapy and tanning beds.

• Smoking.

• HPV exposure.

• Exposure to ionizing radiation.

• Arsenic exposure.

• Fair skin.

• Age older than 60 years.

• Male gender.

• Living at lower latitude and ...