Application of anatomical and histological features of testis to age estimation

In forensic practice, when parts of an unidentified human body are found, age estimation with limited materials is required. This study investigated age-related anatomical and histological changes in testes to evaluate their applicability for forensic age estimation. Testicular samples from 228 male autopsy cases (aged 0-96 years) were analyzed. The Johnsen score, testicular weight, basement membrane thickness, number of seminiferous tubules per field, and percentage of hyalinized tubules were examined. Basement membrane thickness showed a strong positive correlation with age across all subjects (r = 0.733). In individuals under 20 years, testicular weight was positively correlated with age (r = 0.89), while the number of seminiferous tubules negatively correlated (r =  - 0.90). In those aged ≥ 20 years, Johnsen score, testicular weight, and hyalinization rate showed significant age-related differences between groups. Receiver operating characteristic curve analysis identified cutoff values for age discrimination: hyalinization rate of ≥ 9.0 % for ≥ 60 years (sensitivity 69.7 %, specificity 89.5 %), and testicular weight of ≤ 10.1 g for ≥ 80 years (sensitivity 85.7 %, specificity 73.3 %). Basement membrane thickness, testicular weight, and seminiferous tubule count are useful indicators for forensic age estimation under 20 years of age; on the other hand, basement membrane thickness, testicular weight, and hyalinization rate are more informative in individuals aged ≥ 20 years. These findings suggest the potential contribution of these indicators to forensic age estimation, while further studies are needed to validate their practical applicability.