Regression structures

Dermoscopic Description
White scar-like depigmentation (lighter than the surrounding skin) and/or “peppering” (speckled multiple blue-gray granules).

What the structures correspond to histologically
Fully evolved regression shows fibrosis and melanosis (infiltrate of melanophages), and sparse lymphocytic infiltrates. The normal undulating DEJ pattern formed by rete ridges and dermal papillae is attenuated to become completely flattened. 

Lesions in which the structures arise
Regression structures consisting of both scar-like depigmentation and peppering (granularity) should raise suspicion for melanoma. Regression structures consisting of only peppering can be seen in melanoma, lichenoid keratoses and naevi. In lichenoid keratoses the granularity tends to be coarse and diffusely distributed. In melanocytic lesions the granularity tends to be finer and focally distributed. These areas should not be chosen for sectioning when grossing a suspected melanoma as they may reveal non-diagnostic features or underestimate the Breslow thickness.