The mysteries of calcified remains: distinction and recognition of atherosclerotic calcifications, ossified cartilage, calcified pleural plaques and gallstones

Markers of disease on skeletal remains are valuable tools in both forensic sciences and archeology. However, not all pathologies leave direct signs on bones that can be interpreted. Some are responsible for the formation of calcified material that have the potential to survive the decomposition processes. These products of disease are difficult to recognize, especially when mixed with soil and altered by taphonomic processes; they may be considered non- relevant for the anthropological analysis because they can be more insidious (in particular when not in situ) and are less well known. We aimed in providing additional information on the appearance of calcified soft tissue material in order to help anthropologists pay more attention to them and identify them. In this perspective, we performed morphological, SEM and histological (according to two protocols: decalcified and undecalcified) analyses on known calcified soft tissue material collected from fresh cadavers and “aged” by water maceration so as to simulate a dry bone context. When available, we compared them with dry bone calcifications recovered among skeletal remains. The calcified material selected included atherosclerotic calcifications, ossified cartilage, gallstones and pleural plaques. Atherosclerotic calcifications are convex-concave plaques with a stratified structure observed in detail in the SEM and histological analyses. Moreover, decalcified sections showed cores of extracellular lipids constituted of cholesterol crystals, surrounded by macrophage foam cells that appeared as ‘ghost’ elements. Ossified cartilage, although similar to bone in appearance, exhibited both lamellar bone and mineralized matrix in histological sections. Histologically, parietal pleural plaques show a soft component made of dense layers of avascular collagen with occasional fibroblasts and a hard component formed by amorphous dense acellular material similar to fibrotic/hyalinized tissue. The boundary between plaque and pleura showed small vessels surrounded by dense thickening of lymphocytes and fibro-adipose tissue. Gallstones can present various shapes, sizes, colorations and elemental compositions, but cross-sectional studies may allow their recognition and classification according to their main component: cholesterol, calcium bilirubinate or mixed. A correct identification of these calcified material will provide specific information to the biological profile, which is one of the main objectives in forensic anthropology. For instance, atherosclerotic plaques act as markers of cardiovascular disease, ossified cartilage may be an indicator of age-at-death, gallstones can be compared to antemortem data and pleural plaques may be indicative of pulmonary disease.