Nonlinear optical imaging as a diagnostic tool for cutaneous squamous cell carcinoma

The global incidence of squamous cell carcinoma in skin has been rising lately due to increased exposure to ultraviolet radiation from sunlight or indoor tanning salons. If diagnosed late, this can lead to significant patient morbidity and an increased burden to health care. Therefore early detection of squamous cell carcinoma in skin can ensure adequate preventive and therapeutic measures for the patient. Conventional diagnostics of skin cancer involve biopsies of the skin lesion that is invasive for patients. Biopsy of a benign skin lesion leads to cosmetic scarring in the patient and unnecessary workload for the pathologist. In contrast, skipping biopsy of a malignant skin lesion can prove harmful for the patient. Therefore there is a dire need for non-invasive diagnostic modalities that can aid the clinician to (i) detect early cancer-related changes in skin and (ii) determine the need of biopsy for the observed skin lesion. This thesis explores the potential of nonlinear optical imaging as a non-invasive tool to detect early cancer related changes and diagnose squamous cell carcinoma in skin. The results in this thesis show (i) nonlinear optical imaging is a safe diagnostic modality with radiation related risks to be negligible above the same risk from regular sun exposure, (ii) nonlinear optical imaging can non-invasively detect early microscopic changes in the preclinical stage of skin carcinogenesis itself and (iii) This imaging modality can additionally acquire spectral information and detect spectral changes between normal skin, skin with preclinical cancerous changes and clinically visible skin tumours.