Coal forms from the accumulation of plant debris, usually in a swamp environment. When plant debris dies and falls into the swamp the standing water of the swamp protects it from decay. Swamp waters are usually deficient in oxygen, which would react with the plant debris and cause it to decay.
Porokeratosis is generally considered to be a benign condition though malignant transformation has been seen in all but the punctate variety, necessitating regular followup of patients with porokeratosis (Maubec et al., 2005; Sasson & Krain, 1996).
Benign. 1  Viral wart. 2  Seborrhoeic keratosis (waxy scale / cerebriform or stuck-on appearance / bits can drop off) 3  Verrucous keratosis (features of both a viral wart and a seborrhoeic keratosis)  Chondrodermatitis nodularis helicis (a tender lesion on the pressure points of the ear, due to laying on one side in bed)