Histopathological and ultrastructural study on face lesions of eleven cases with melasma

Objective: To study the histopathological features of facial melasma skin in comparison with adjacent normal skin.Methods: Biopsies were taken from both melasma lesional skin and adjacent perilesional normal skin in 11 cases with melasma.The sections were stained by using haematoxylin and eosin,Fontana-Masson and immunostaining for melanocytes.The ultrastructure of the skin was also examined.Results: The amount of melanin was significantly increased in all epidermal layers in melasma skin.The staining intensity of epidermal melanocytes increased in melasma lesions.But the number of melanocytes was not changed.Melanosomes increased in number and were more widely dispersed in the keratinocytes of the lesional skin.Lesional melanocytes had many more mature melanosome,mitochondria,Golgi apparatus,rough endoplasmic reticulum and ribosomes in their cytoplasm.Conclusion: Melasma is characterized by epidermal hyperpigmentation,which are possibly caused both by an increased activity of melanogenic enzymes and by an increased function of melanosome transfer.