In forensic practice, it is doubtless that wound examination is one of the consequential and necessary areas for forensic pathologists. During the process of wound investigation, to assess the causalcorrelation between death and any wounds, forensic pathologists are always required to differentiate antemortem wounds from postmortem damage or to estimate wound age. It is likewise important to figure out whether a wound has vital reaction, and if so, how long before the wound has been sustained [1] . In other words, the determination of wound vitality or wound age has to be always performed. The short and simplified overview of wound healing can be adopted to determine wound vitality or wound age in forensic medicine. Forensic pathologists can determine how long a victim has been exposed by the age estimation of burns. However, aging of burn injuries by visual observation is sometimes difficult and uncertain [2] [3] .

Histopathological examination remains to be a more reliable technique, which provides an experimental basis for the distinction between ante- and post-mortem wounds, and determining the age of wounds [4] . Histo- pathological alterations characterizing the distinctive phases of wound healing can be applied to estimate the approximate age of wounds, especially of those inflicted within the early hours of wounding [5] . Therefore, aging of burn wounds is one of the most important medico-legal problems based on the observation of a normal course of the burn healing process. During the healing process, several morphologically distinguishable pheno- mena occur, and their microscopical detection determines the wound age whereas the absence of these para- meters provides fewer reliable results and often cannot be interpreted under forensic aspects [2] [4] . In this way, the following study aimed to recognizethe pathomorphological changes in healing of chronic deep second- degree burns that may be more constant in their time sequence, thus enabling an assessment of the burn wound vitality and age.

Under the light microscope, the normal intact skin reveals epidermis lined by stratified squamous epithelium with all layers; granular, basal, spinous and cornfied layers. The dermis is intact containing blood vessels and few lymphocytes (Figure 1). In relation to intact skin, all burn wounds were noted to involve deep dermis and the pathological changes of burn wounds at distinct time phases were almost different. On 7th day post-burn, the dermal and epidermal layers are disorganized with granulation tissue formation around sebaceous glands (Figure 2(a)). The superficial necrotic tissues in the dermis were liquefied, discharged and thinned. The epider- mis became necrotic due to collagen degeneration and granulation tissue formation. In addition, neoformative small-sized blood vessels with presence of fibroblast and infiltration of many inflammatory cells, including neutrophil, lymphocytes, polymorphs and histocytes were visible in wounds (Figure 2(b)). On 12th day post- burn, the wound character is still clearly similar to 7th day post-burn. However, the burn showing fibrinoid necrosis with degeneration of collagen and sebaceous gland (Figure 3(a) and Figure 3(b)).

On 17th day post-burn, the burn wound is showing partial surface ulceration with epidermal necrosis and loses. It was infiltrated with fibroblast, histocytes, lymphocytes and polymorphs (Figure 4(a)). The dermis shows disorganization with collagen and degeneration of the sebaceous gland (Figure 4(b)). On 21st day post- burn, the burn wound is showing partial surface ulceration with dermal granulation tissue formation (Figure 5). On 28th day post-burn, the epidermis becomes thin with dermal disorganization, fibrous tissue formation and degeneration of the hair follicle (Figure 6(a) and Figure 6(b)).

From the viewpoint of forensic pathology as well, these pathomorphological changes show the possibility of available timing for wound age determination. Normal wound healing is usually divided into three stages: 1) inflammation, 2) epithelialization and granulation tissue formation, and 3) matrix formation and remodeling [7] [8] . Chronic wounds are characterized by a prolonged inflammatory response with disturbed cellular consti- tuents [9] [10] . Histologic examination of the burn edge, to include both the burned area and adjacent grossly unburned skin, may reveal vital reaction microscopically, consisting of acute inflammation, edema, and necrosis [11] [12] . These findings are present only in antemortem burns, thereby assisting in the delineation of whether the decedent was alive when the burns occurred. Additionally, a section of the skin in burns may document necrosis, vertical streaming of the epidermal nuclei, and homogenation of the dermal collagen. Our study demonstrated that the histopathological changes of burn wounds involved deep dermis and the pathological changes of burns at distinctive time phases were almost different in comparing to normal intact skin. On days 7 - 12 post-burn, the pathomorphological change was characterized by the disorganization with granulation tissue formation and necrosis of occurred in the burned epidermis and superficial dermis, revealing inflammatory response, with signs of “leukocyte infiltration”. The necrotic tissue began to liquefy and discharge increasingly as the disease course progressed [12] . Such changes increased around days 12 - 17 post-burn when dermal degeneration of sebaceous gland, fibroblasts, histocytes, as well as other repaired cells, showed signs of regene- ration.

On 7th day post-burn, wound liquefaction became noticeable and peaked. After that, liquefaction reduced with less necrotic tissue. The inflammatory response, however, remained correlated with the liquefaction of necrotic tissue. Repair by regeneration was noted on 12th day post-burn and manifested mainly by fibroblasts, histocytes, as well as other repaired cells. This stimulated the proliferation of peripheral fibroblasts and endothelia, and further formed granulation tissues, leading to final healing by epithelization [8] [12] . Later, the surface of burn wound is partially ulcerated with epidermal necrosis, dermal disorganization and degeneration of the sebaceous gland 17 - 21 days post-burn. After experiencing further differentiation and neoformation, the regenerated skin finally attained the structure of normal skin at 28th day post-burn. In this way, the study demonstrates that recognizing the histopathological changes in normal healing process of burns is more constant in their time sequence, thus enabling an assessment of the burn wound vitality and age. Such age estimation of burn wounds is vital when a cadaver or a burnt body has many burns of different ages, particularly in criminal cases.

Yasser S.El-Sayed, (2016) Time Course of Histomorphologic Features during Chronic Burn Wound Healing. Forensic Medicine and Anatomy Research,04,1-6. doi: 10.4236/fmar.2016.41001