Improving the histological quality in cadaveric skin and liver for post-mortem interval teaching and research

TRABAJO LIBRE SOMETIDO AL III CONGRESO DE CIENCIAS FORENSES DE HONDURAS DEL 8 AL 10 DE OCTUBRE, TEGUCIGALPA, HONDURAS

Abstract

Introduction: The post-mortem interval (PMI) is one of the primary goals in the investigation of human and animal death, in a medico-legal context, and consists of the period of time elapsed from death to the moment of discovery of the corpse or carcass. Its precise determination remains one of the greatest challenges in forensic medicine, as it is influenced by both extrinsic and intrinsic factors. Histological analysis has a high potential for determining PMI, being opportune to carry out further studies aimed at evaluating PMI in organs, like the skin, considered a gold standard tissue in forensic investigation, and the liver, one of the organs commonly collected in the autopsy. The purpose of this research is to improve the histotechnical quality of skin and liver samples, as well as to analyse the added value in estimating the PMI and generating teaching materials.

Methodology: The study included 20 carcasses of Large White domestic pigs, originating from necropsies performed at ICBAS-U. Porto, and 20 Caucasian humans, from autopsies performed at the National Institute of Legal Medicine and Forensic Sciences, North Branch, Porto, with known or expected PMI, from which skin and liver samples were taken. Data on pig carcasses and human cadavers, including sex, age, weight, cause of death, and known or expected PMI, were also gathered. The samples were fixed in 10% neutral buffered formalin, and embedded in paraffin and methacrylate. They were then stained using HE, PAS, and Goldner’s Masson trichrome. All slides were evaluated using optical microscopy, and histological changes at different times after death were noted to define a scoring system for each organ and species.

Results: After optimising the protocol and analysing the slides, scoring systems were constructed. For skin, the scoring system consisted of three grades in both species, considering changes in the epidermis, dermis, sweat and sebaceous glands, and vascular structures. For liver, five grades were established for pig samples and three for humans, based on changes in architecture, hepatocytes, and portal areas. The degradation was less noticeable in the skin, with better delineation of histological features in humans. In pig liver, a greater disparity in deterioration was observed, particularly in hepatocytes and sinusoids, as well as in hepatic lobule architecture, except for the hepatic lobules in human samples. Goldner’s Masson trichrome stain facilitated the observation. The paraffin sections allowed for a more straightforward observation and recognition of certain histological features, while the methacrylate sections provided better preservation of these features.

Discussion and conclusions: In light of the literature, we conclude that our observations in skin and liver samples from necropsies or autopsies reinforce their strong potential as PMI indicators and practical teaching materials. Methacrylate adds structural refinement. However, additional cases are needed to draw more robust conclusions regarding the variables studied.