Melanization in basal cell carcinomas: microscopic characterization of clinically pigmented and non-pigmented tumours.

Clinical and microscopic pigmentation may affect the treatment outcomes in basal cell carcinoma. However, there have not been any in-depth histopathological comparisons between clinically pigmented and non-pigmented basal cell carcinomas with regards to microscopic melanization. The aims of our study were to determine the proportion of pigmented basal cell carcinomas presenting to the National Skin Centre in Singapore, to characterize the histological pattern of melanization and to perform a semi-quantitative analysis of the degree of microscopic melanization of the tumours. Patients with clinical features and histologically confirmed basal cell carcinomas were recruited. Demographic data and clinical characteristics were recorded and basal cell carcinoma sections were examined for histological subtype and pattern of melanization. Twenty-five Chinese patients with 30 basal cell carcinomas were recruited. Three of the five clinically non-pigmented and all of the clinically pigmented basal cell carcinomas had microscopic evidence of melanization. Microscopic melanization in clinically non-pigmented basal cell carcinomas was present only focally or in the centre of the tumour mass. Both groups of basal cell carcinomas may be colonized by melanocytes. Two morphological types of melanocytes, a dendritic and round cell type, were identified. Future research is required to evaluate if the degree of microscopic melanization influences the treatment outcome of basal cell carcinomas.