Melanoma and naevi with a globular pattern: confocal microscopy as an aid for diagnostic differentiation

Abstract

Background: Dermoscopically, one of the most common findings in melanocytic lesions is a globular pattern. A regular globular pattern is a common finding in naevi. Melanoma can also show a globular pattern, with globules typically irregular in size, colour and distribution.

Objectives: To investigate the likelihood of diagnosing melanoma according to distinct dermoscopic and confocal aspects.

Methods: Dermoscopic and confocal aspects of 83 excised melanocytic lesions dermoscopically showing globules were analysed.

Results: Our study population included 39 acquired melanocytic naevi, 16 Spitz naevi and 28 melanomas. Univariate analysis showed that regular distribution of globules on dermoscopy is associated with a ninefold lower risk for melanoma, whereas an irregular distribution is associated with an almost 10-fold increased risk for melanoma. Concerning confocal features, dense nests are associated with a fivefold lower risk for melanoma, whereas loosely arranged nests are associated with an almost sixfold risk for melanoma; moreover, the presence of round cells is associated with a 17-fold lower risk for melanoma, whereas pleomorphic cells are associated with an almost 16-fold risk for melanoma.

Conclusions: So that melanoma is not missed, clinicians should carefully analyse globular lesions in adults, focusing, in particular, on the distribution of globules and on the presence of confocal cytological atypia.