In vivo reflectance confocal microscopy for evaluating seborrheic keratosis, verruca plana, syringoma and lichen nitidus.

Background: In clinical, common facial papule dermatosis such as seborrheic keratosis (SK), verruca plana (VP), syringoma and lichen nitidus (LN) is often misdiagnosed. Summarizing in vivo reflectance confocal microscopy (RCM) features of the facial papule dermatosis is helpful in the diagnosis of ambiguous lesions. The purpose of this study was to evaluate the features of SK, VP, syringoma, and LN in RCM.

Methods: We recruited 144 patients referred for unequivocal facial papule dermatosis including 60 patients with SK, 60 patients with VP, 10 patients with syringoma, and 14 patients with LN. The RCM images were evaluated at the epidermis, the dermoepidermal junction, and the dermis from both papule lesions and normal skin.

Results: In the epidermis, the cerebriform shape was the main RCM characteristic of SK and the "petal-like" structure was the main RCM characteristic of VP. In the dermoepidermal junction, the RCM features we found were as follows: For SK, the bright dermal papillary rings, the abnormal dermal papilla and the looped vessels were also observed at the abnormal dermal papilla. For VP, the bright dermal papillary rings and the point-like blood vessels were also observed at the round dermal papills. For LN, the round, enlarged, well-circumscribed dermal papillae and the enlarged dermal papillaes were heavily laden with individual highly refractive cells. In the dermis, RCM examination revealed brightly refractile teratogenous sweat tube, designing variably visible bright "moon" structures in all syringoma patients.

Conclusion: Considering our results, RCM may be useful to non-invasively discriminate SK, VP, syringoma and LN in vivo.