Thick lines reticular or branched

This feature is found where the outline of the network is much thicker than that of the rest of the lesion or the surrounding background skin. They represent atypical melanocytes expanding the rete ridges. We see  a lot of reticulated networks because we look at a lot of nevi.  Remember though that some non melanocytic lesions can exhibit a network eg Solar lentigo (with increased melanocytes at the DEJ), reticulated Seb k, Dermatofibroma, Ink spot lentigo and Accessory nipple! 
Non the less a thickened network is a good clue to melanoma within a pigmented lesion when you have a thinner network to compare it to!