The blue globular pattern in dermoscopy

Seborrheic keratosis (SK) is a frequent benign epithelial skin tumor. Generally its diagnosis is clinical, however SK can sometimes clinically simulate a melanocytic lesion; therefore we need dermoscopy to reach a correct diagnosis. Milia-like cysts and comedo-like openings are the common dermoscopic features of SK, but it is not a rare finding that SK can display one or more dermoscopic patterns suggestive of a melanocytic origin.

We describe a case series of SKs with a blue globular pattern simulating a melanocytic lesion.

We retrospectively evaluated 224 SKs seen during 2011 at the Dermatoscopy Unit of the Department of Dermatology, University of Rome 'Sapienza'.

Five SKs showed a blue globular pattern, without the SK main features generally seen in dermoscopy; globules were multiple, round or oval, well-demarcated, small and medium-sized, blue-colored and equally distributed within the lesion. Histopathologic examination was consistent with acanthotic SK.

Identification of the blue globular pattern can be helpful for the dermoscopic diagnosis of SK, especially when its common dermoscopic features are absent.