A histological approach to the identification of calcified soft tissue material in skeletal remains, procedures distinguishing atherosclerotic plaques and ossifying costal cartilage

The identification of calcified soft tissue and cartilage in skeletal human remains may be a challenging task. Calcified or mineralized pleurae, arteries, muscular tissue, to name a few, may indicate diseases interesting for the reconstruction of the past; calcified or mineralized cartilage may also be frequently found alongside skeletal remains, but may be difficult to differentiate from calcified soft tissue. Research particularly through microscopy is needed to identify the origin of such small “hard” fragments. In light of the paucity of data in literature, we began with documenting the morphological and histological aspects of atherosclerotic plaques and ossifying costal cartilage. Our study examines 15 samples of atherosclerotic calcifications (plaques) and ossified costal cartilage from skeletal remains of the CAL Milano Cemetery Skeletal Collection, an identified collection constituted of unclaimed skeletonized remains. Samples were processed for histology according to two protocols (calcified and decalcified). Calcified samples were processed in Pertex and let to solidify for 72 hours. Decalcified samples were fixed in formalin, decalcified in Decal (14% hydrochloric acid) and embedded in paraffin after dehydration. Sections of 5 μm were cut and stained with Hematoxylin and Eosin. The histological results displayed distinguishing features for both plaques and cartilage. Plaques even from dry skeletal remains showed a stratified structure with cholesterol crystals and the clearly identifiable “ghost” elements of macrophage foam cells. Ossified cartilage showed the transition phases from cartilage to bone, mainly through the presence of new osteons and the “ghosts” of isogenic cell groups. This presentation provides histomorphological documentation regarding the characteristic features of atherosclerotic calcifications and ossifying cartilage - valid tools for the identification of calcified soft tissues associated with skeletal remains.