Comparative Morphometric and Histological Assessment of the Human Thymus in Young and older Individuals

Abstract

Objective: To examine and compare selected morphological and histological parameters of the human thymus gland in young and older individuals, with particular emphasis on thymic capsule thickness, interlobular connective tissue thickness, and the number and size of Hassall's corpuscles.

Study Design: Comparative observational study.

Methodology: A total of 125 human thymus specimens were included and divided into two age groups: 63 individuals younger than 30 years and 62 individuals aged 45–60 years. Specimens were fixed in 10% buffered formalin, routinely processed, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Histological assessment included capsule thickness, interlobular connective tissue thickness, Hassall's corpuscle number and diameter, adipose replacement, and corticomedullary architecture.

Results: In the illustrative dataset, mean capsule thickness was 128.7±27.4 µm in the young group versus 214.6±39.8 µm in the older group (p<0.001). Mean interlobular connective tissue thickness was 91.5±24.6 µm versus 176.3±42.1 µm (p<0.001). Hassall's corpuscles were fewer in older specimens (6.1±1.8 vs 9.4±2.3 per field) but larger (82.5±18.7 vs 54.8±13.6 µm), both p<0.001.

Conclusion: The findings illustrate prominent age-associated morphological remodeling of the thymus, including connective-tissue expansion, adipose replacement, architectural alteration, and changes in Hassall's corpuscles.

Keywords: Human thymus; thymic involution; aging; Hassall's corpuscles; thymic capsule; connective tissue; histology; immunosenescence.