On the other hand, mineral deposits, secondary to necrosis, are attributed to the commonly observed but complex process of dystrophic mineralization. Dystrophic mineralization is often seen as lamellar calcospherites found secondary to small clustered regions of neuronal necrosis at various neural sites, such as depicted in Figure 3 and Figure 4. Figure 3 shows the aggregation of mineralized bodies (arrow) in sites of former granule cell necrosis in the cerebellum. Note the loss of neural tissue represented by spaces formerly occupied by internal granule cells, and the presence of multiple small, dark, round bodies. The presence of such mineralized foci may lead to disruption of the tissue during microtomy. The mineralized foci shown in Figure 3 should not be confused with the artifactual presence of boney spicules often carried into brain from overlying skull fragments during brain extraction/trimming or with heterotopic bone tissue. The round, often concentric, lamellar appearance of calcospherites, shown at higher magnification in Figure 4, is typical of late stages of mineralization of necrotic brain tissue. Calcospherites are deposited in a region of former cerebellar internal granule cell necrosis. Note the concentric laminated structures (arrow) of the larger bodies that are apparently absent in smaller ones. The deposition of mineral in the form of calcospherites in these cases requires several weeks to form after the necrotizing insult.
Figure 5 shows a region of prior necrosis adjacent to piriform cortex with an uncommon reactive focus of osteoid (arrow) and ossification (arrowhead). A large zone of brain necrosis is replaced by a progression of mineralized bodies of several types. To the right are some smaller basophilic calcospherites, and to the left are larger zones of necrotic brain tissue transformed into both osteoid, composed of pink hyaline material, and a more advanced stage of osseous metaplasia, where dense basophilic mineral and osteocytes are apparent.
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