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).
It is a benign tumor. When the bone tumor grows on other bone it is known as homoplastic osteoma; when it grows on other tissue it is called heteroplastic osteoma. Osteoma represents the most common benign neoplasm of the nose and paranasal sinuses.t is a benign tumor. When the bone tumor grows on other bone it is known as homoplastic osteoma; when it grows on other tissue it is called heteroplastic osteoma. Osteoma represents the most common benign neoplasm of the nose and paranasal sinuses.