The differential diagnosis of lentiginous lesions can be challenging. It has been written that solar lentigo is the nascent lesion for seborrheic keratosis. Solar-lentigo generally features compact orthokerotosis with little melanin in the keratin layer (arrow 2), epidermal hyperplasia with bulbous rete ridges, pigmented keratinocytes especially prominent at the bulbs of the rete ridges (arrows 1).
Melanocytes are generally not found in the epidermis (the absence of melanocytic hyperplasia is a key feature in this entity). Mild chronic inflammation may be present but often without pigment laden macrophages in the dermis. Lamellar collagen around the rete pegs is absent. While key features exist, the lack of melanocytic hyperplasia, the presence of bulbous tips, but also in contrast to some writings, there are numerous pigmented melanophages that are perivascular.