The purpose of this study is to correlate pathological features from specimens in order to determine if this new molecular diagnostic technique can be used to detect risk of skin cancer.

Squamous cell carcinoma is the culmination of a multistep carcinogenesis process that is preceded by early stages referred as squamous dysplasia and actinic keratosis. Squamous dysplasia (SD) also known as "field effect" is clinically characterized by xerosis (dry, scaly skin), lentigines and uneven pigmentation. While morphologically skin biopsies and cytology samples show only minimal changes, at the molecular level it is known that SD is characterized by small clone keratinocytes carrying mutations of the P53 gene. An optical technology called Partial Wave Spectroscopy (PWS) probes nanoscale structures in the order of tens to a few hundred nanometers. PWS is a light back-scattering techniques that uses light reflected off of a tissue sample. The measured biomarker is sensitive to the cytosolic and nucleic architecture within the cell and quantifies the nanoscale disorder, which conventional light microscopy fails to appreciate. PWS has allowed to identify various grades of structural disorder at the nanoscale level of colonic and pulmonary premalignant cell samples. Using PWS we aim to study the spectrum of cutaneous SD from patients at high risk for SCC development. Since squamous dysplasia is difficult to assess with routine histology and cytopathology and a grading system for squamous dysplasia by routine histology or cytology is not available, we propose to assess the value of PWS as a new and more sensitive imaging technique. By identifying the degree of SD at the molecular level, we may be able to intervene with close surveillance, early treatment and chemoprevention strategies to achieve lower morbidity by means of fewer and smaller skin cancers.

Inclusion Criteria:

• 18 to 89 years old, male and female, Fitzpatrick skin phototype I - III
• Photodamage skin grades 3 - 4 (global assessment)
• Medical history of precancerous lesions and or known history of SCC or healthy volunteers

Exclusion Criteria:

• Subjects under 18 years old
• Pregnant women or lactating mothers
• Treatment with systemic chemotherapy within 4 weeks period before consent
• Known HIV+ patients (self-reported)