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Epiluminescence videomicroscopy: black dots and brown globules revisited by stripping the stratum corneum
J F Guillod1, A M Skaria, D Salomon
1Department of Dermatology, University Hospital Geneva, Switzerland.
Background:
The pattern and distribution of several elementary structures, such as black dots and brown globules, observed by epiluminescence microscopy (ELM) are valuable to the diagnosis of pigmented lesions. Black dots are considered to be focal accumulations of melanin in the stratum corneum, and brown globules are thought to be clusters of nevocytes at the dermoepidermal junction. Because of their distinct locations within the layers of the skin, black dots might be removed by stripping of the stratum corneum whereas brown globules should not.
Objective:
Our purpose was to evaluate the efficacy of ELM features to identify brown globules and black dots and to analyze the relation of these structures within the pigmented network.
Method:
The distribution and number of black dots and brown globules from 27 benign melanocytic lesions were analyzed by videomicroscopy before and after a stripping procedure. Several lesions were observed for months to see whether the pattern before stripping is reconstituted.
Results:
Before stripping, 549 black dots and 214 brown globules were identified by means of three criteria: color, contour, and size. Ninety-eight percent of black dots were superimposed on the gridlines of the pigmented network. Stripping removed 56% of black dots and only 10% of brown globules. Eighty-two percent of the black dots that could be stripped were superimposed on the gridlines of the pigmented network. On follow-up, both black dots and brown globule-like structures previously removed by stripping were restored at their initial locations within a few months after stripping.
Conclusion:
The close association of black dots with the gridlines of pigmented network should be taken as one criterion to identify black dots. Half the structures identified as black dots by ELM are not localized in the stratum corneum but rather correspond to vertical stacking of pigment within the epidermis. Accumulation of melanosomes in the stratum corneum may take the appearance of brown globules.