Histopathologically, Abscess is defined as

(A) Localised collection with necrotic cells surrounded by the dead tissue # ABSCESS: is a collection of pus that has built up within the tissue of the body. Abscess shows redness, pain, warmth, and swelling with fluid filled. Area of redness often extends beyond the swelling It is a localized collection of pus (purulent inflammatory tissue) caused by suppuration buried in a tissue, an organ, or a confined space, lined by pyogenic membrane.> Gangrene is a type of necrosis caused by a critically insufficient blood supply. This potentially life-threatening condition may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood supply to the affected tissues, which results in cell death.> Cellulitis It is a bacterial infection involving the inner layers of the skin. Specifically affects the dermis & subcutaneous fat Signs & symptoms -- area of redness which increases in size over a few days. Borders of the area of redness are generally not sharp and the skin may be swollen. Redness often turns white when pressure is applied, this is not always the case. The area of infection is usually painful. Neoplasm is an abnormal growth of tissue, which if it forms a mass, is commonly referred to as a tumour or tumor. Prior to the abnormal growth of tissue, as neoplasia, cells often undergo an abnormal pattern of growth, such as metaplasia or dysplasia