Expression of inducible nitric oxide synthase in cutaneous adnexal tumours of the head and neck.

Adnexal tumours are a rare heterogeneous group of neoplasms, most commonly found in the head and neck region. Although most are benign, malignant adnexal tumours often behave aggressively, resulting in early metastasis. There is increasing interest in the role that nitric oxide (NO) plays in the behaviour of many cancers. It is thought that NO, produced by the enzyme inducible NO synthase (iNOS), facilitates tumour growth and dissemination. iNOS has been studied in the common skin cancers, where its expression correlates with tumour behaviour, but it has not been previously investigated in cutaneous adnexal tumours. An immunhistochemical study was performed using a monoclonal antibody to iNOS in 37 cases of adnexal tumours (19 benign, 18 malignant). iNOS expression was weakly expressed by basal keratinocytes of adjacent skin in all cases and it was variably expressed in the tumours. Malignant tumours had significantly increased iNOS expression when compared to both adjacent skin (P<0.001) and the benign tumour group (P<0.001). No significant difference was found between iNOS expression in benign tumour and adjacent skin (P=0.5). The role of iNOS in this rare group of tumours and the possibility of pharmacologically inhibiting it in the clinical setting warrants further investigation.