Comparative morphologic study of calcifications in the pineal gland and choroid plexus of the human brain

Background: Calcifications are frequently observed in the brain during radiologic evaluations and postmortem histologic examinations, most commonly in the pineal gland and choroid plexus. An increase in the number and size of calcifications has been associated with various neurologic, oncologic, infectious, and other diseases. Current evidence suggests a potential role of calcifications in the pathogenesis of conditions such as vascular dementia, Alzheimer disease, Parkinson disease, astrocytomas, posttraumatic epilepsy, and migraine. However, the causes and mechanisms of calcification formation in the brain remain unclear. Aim: This study aimed to examine the morphologic features of calcium concretions in the pineal gland and choroid plexus—the two primary sites of their occurrence—to identify possible microstructures associated with calcification. Methods: The study was conducted on 14 samples of choroid plexus tissue (from individuals aged 20–63 years) and 12 samples of pineal gland tissue (aged 16–61 years). Histological sections were stained with alum hematoxylin and aniline blue. Immunohistochemical analysis was performed using monoclonal anti-Vimentin antibodies (clone SP20). Results: Calcifications were identified in all pineal gland samples and in 13 of 14 choroid plexus samples. In the pineal gland, calcification size varied widely (5–20 µm to 150 µm), predominantly occurring in lobules among pinealocytes, and much less frequently within connective tissue trabeculae. In the choroid plexus, calcifications ranged from 30 to 70 µm (occasionally up to 100 µm) and were primarily located within the connective tissue stroma, rather than the villi. Brain sand was found exclusively in the pineal gland, but not in the choroid plexus. A Vimentin-positive capsule was found around psammoma bodies in both the pineal gland and choroid plexus, but was absent around amorphous calcifications of the choroid plexus. Conclusion: The predominant localization of choroid plexus calcifications in collagenrich connective tissue, and beyond this tissue in the pineal gland, supports the hypothesis of two distinct calcification mechanisms: one collagen-associated and the other independent of collagen. The presence of brain sand in the pineal gland—but not in the choroid plexus of adults—suggests that pineal calcification is a continuous process, whereas calcification in the choroid plexus may predominantly occur post-puberty. The presence of two types of calcifications that differ in both structure and the presence/absence of a capsule, i.e., psammoma bodies and amorphous calcifications, respectively, may indicate a possible pathologic (mechanical) effect on the surrounding tissues by psammoma bodies, but not amorphous calcifications, which is prevented by the formation of an insulating layer.