Dermoscopy of haemosiderotic/aneurysmal dermatofibroma: A morphological study of 110 cases.

BACKGROUND: Haemosiderotic and aneurysmal dermatofibromas are uncommon and frequently misdiagnosed lesions, which can be considered as different histopathological stages of the same tumour. A dermoscopic diagnosis testing accuracy has not been performed for these tumours to date. OBJECTIVES: To determine the diagnostic significance of dermoscopic structures and patterns associated with haemosiderotic/ aneurysmal dermatofibromas in a large series. METHODS: Dermoscopic images of histopathologically proven cases of 110 haemosiderotic/ aneurysmal dermatofibromas and 501 other tumours were collected. The frequency, sensitivity, specificity, positive predictive value and negative predictive value of the dermoscopic structures and patterns associated with these lesions were calculated. RESULTS: Haemosiderotic/ aneurysmal dermatofibromas are mostly symmetric lesions (86.5%), and a prominent homogeneous area was present in 100% of them. The presence of vascular structures was very common (86.4%), and dotted vessels were predominant (58.2%). Shiny white structures were seen in 85.5% of lesions, while a peripheral delicate pigment network was present in 69.1%. The most significant pattern was the one composed of a prominent homogeneous area and peripheral delicate pigment network, which showed a specificity of 100% with a relatively good sensitivity (69.1%). All the patterns containing a peripheral delicate pigment network showed very good specificities, positive predictive values and negative predictive values. Those patterns without a peripheral delicate pigment network showed the highest sensitivities, but they showed a significant overlap with other tumours, mainly with melanoma. CONCLUSIONS: Dermoscopy is helpful in improving the diagnostic accuracy of haemosiderotic/ aneurysmal dermatofibromas. However, there is a considerable dermoscopic overlap between these tumours and melanoma, specifically when the peripheral delicate pigment network is absent.

Pyogenic granuloma clinically and dermoscopically mimicking pigmented melanoma.

Pyogenic granuloma is a common, benign, acquired, vascular growth of skin and mucous membranes that usually presents as a solitary, rapidly, growing, papule or polyp that bleeds easily after minor trauma. The clinical diagnosis of this lesion is usually straightforward. Moreover, the dermoscopic features associated with pyogenic granulomas have been described recently. However, occasionally this tumor can be difficult to differentiate clinically and dermoscopically from other pigmented and vascular lesions. We report the case of an 18-year-old male who presented with a round, purple-black nodule with hemorrhagic crust, 1 cm in diameter, located on the lower part of the thorax. Dermoscopic evaluation revealed the presence of a blue-white veil, a black blotch, polymorphous atypical vessels, milky-red areas, and hemorrhagic crusts. The subsequent histopathological examination revealed a pyogenic granuloma. We present a case of pyogenic granuloma clinically and dermoscopically indistinguishable from a pigmented malignant melanoma.