Intrapancreatic fat deposition in the elderly: a retrospective cadaveric study with histopathological characterization.

[BACKGROUND] Intrapancreatic fat deposition (IPFD) is associated with pancreatic diseases, such as pancreatitis, type 2 diabetes mellitus, and pancreatic cancer, and so on. Although non-invasive imaging has been used to quantify IPFD in clinical settings, this approach does not fully reflect the incidence and prevalence of IPFD, especially its occurrence in a cohort of elderly individuals, which is difficult to determine from routine medical visits. This study aims to systematically evaluate IPFD in elderly individuals, classify its subtypes, and assess their relationship with other pancreatic lesions.

[METHODS] In the present study, 85 cadaveric pancreatic specimens (median age 88.0 years) without any known pancreatic diseases or prior abdominal surgery were subjected to histopathological and immunohistochemical analyses as needed.

[RESULTS] IPFD was classified into three predominant types: fatty infiltration of the pancreas (FIP), fatty replacement of the pancreas (FRP), and irregular intralobular fatty degeneration (IIFD), with 81% of the cases occurring in the dorsal pancreatic anlage (body and tail, and superior aspect of the head). In a univariate analysis, IIFD showed significant age dependence (p = 0.035), with the prevalence increasing with age (p = 0.088 for trend). FIP was strongly associated with inflammatory cell infiltration (p = 0.001), acinar-to-ductal metaplasia (ADM) (p = 0.003), and pancreatic intraepithelial neoplasia (PanIN) (p < 0.001). In the multivariate analyses, the association between age and IIFD was attenuated and no longer statistically significant (OR 1.044, 95% CI 0.991-1.099; p = 0.106). The association with FIP was also nonsignificant. For PanIN, there was a trend toward higher odds (OR 5.136; p = 0.080), but this did not reach statistical significance.

[CONCLUSION] Our study demonstrated at least three distinct pathological subtypes of IPFD: FIP, FRP, and IIFD. Each has unique histopathological features, developmental mechanisms, and potential pathological significance. In the multivariate analysis, although it did not reach statistical significance, a trend was observed for FIP with PanIN, suggesting its potential role in early pancreatic pathology. Similarly, IIFD showed a non-significant trend toward age dependence, highlighting its possible relevance to age-related pancreatic changes. These findings underscore the need for the pathological distinction of IPFD subtypes in future research on pancreatic aging and disease. Furthermore, the embryological preference of IIFD for the dorsal pancreas and its mechanism deserve further exploration.