Approccio istologico sperimentale con soluzione reidratante di Sandison a tessuti cadaverici carbonizzati

For a forensic pathologist, the autopsy of a charred body represents a scenario that is difficult to handle from several points of view: identification of the victim, chronological determination of the injuries observed, and definition of the dynamics of the event to distinguish whether it is an accident, a suicide, or a homicide/cadaveric destruction. In fact, charring leads to darkening and desiccation of the skin with possible deep lacerations; moreover, when it affects deep tissues, it can cause injuries and a reduction in the volume of internal organs due to desiccation and the expansion of intracavitary gases. In this context, microscopic examination is particularly challenging, not only because fragile, disintegrated, and extremely dry tissues can be easily lost in standard histological examination procedures, but also because the few sections obtained have many technical artefacts. Since the use of various rehydration solutions has been shown to be effective in improving the histological examination of mummified and corified skin specimens, we experimentally applied Sandison's rehydration solution to skin and visceral samples from charred cadavers. Histological specimens observed after hematoxylin-eosin and Masson-Goldner trichrome staining showed qualitatively better morpho-structural aspects compared to those obtained with routine formalin fixation. In parenchymatous viscera, Sandison’s solution partially eliminated the changes caused by severe carbonization with a discrete improvement, while in hollow organs it caused a moderate regeneration of histological structures. Sandison’s solution was particularly effective in skin, brain, and aorta specimens; it caused partial histomorphological recovery of dura mater, esophagus, lung, heart, liver, and kidney. However, spleen and small intestine specimens, in which signs of heat protein coagulation, coarctations, and foci of nuclear pyknosis persisted, were not significantly improved. In addition, the use of Sandison’s solution resulted in a partial recovery of the affinity of the connective tissue dye for trichrome staining: in charred skin specimens not pretreated with rehydration solution, a paradoxal staining of the connective tissue was observed, which appeared red instead of green. This phenomenon, although little known, is reported in the literature and can be fully explained by the extreme destructive power of hyperthermic lesions, which, due to the severe dehydration of the tissue, as in the case of charring, denature the protein structures, leading to conformational changes in the microstructure of collagen and changes in the penetration capacity of dyes in the affected tissues. Sandison's rehydration solution, on the other hand, thanks to an emulsifier - sodium carbonate Na2CO3 - is able to penetrate deeply and homogeneously into the cadaveric tissue and, thanks to a solvent - 96% ethanol - stabilizes the tissue so that it does not collapse and the impaired structures are restored, ensuring better stainability [5]. Thus, overall, the Sandison rehydration procedure is useful and effective and results in high-quality histological sections with less destructive thermal effects, although complete recovery is not always possible. In view of these results, we recommend the use of this procedure in the histological examination of charred skin and viscera specimens.