Expression of nitric oxide synthase-2 in cutaneous squamous cell carcinoma of the head and neck.

Nitric oxide (NO) has a pivotal role in angiogenesis. The expression of NO synthase (NOS2) is down-regulated in basal cell skin cancer but we know of no studies that have investigated its expression in the more aggressive squamous cell skin carcinoma. This immunohistochemical study assessed NOS2 expression in 37 cases of head and neck squamous cell skin carcinoma. NOS2 expression was located in cells of the basal cell layer of epidermis, but was significantly increased in tumour epithelium. No correlations were found between NOS2 expression and tumour size or degree of tumour differentiation. The raised NO concentrations in these tumours may provide one explanation for their more aggressive behaviour than that of the slower-growing basal cell carcinoma.