Morphological heterogeneity in testicular biopsies of infertile azoospermic men: the necessity of bilateral sampling and standardised reporting

Aims To characterise histological patterns and heterogeneity in testicular biopsies from azoospermic men, assess bilateral concordance, evaluate morphometric parameters for a structured reporting template and place findings in context with the existing literature on testicular biopsy evaluation. Methods Retrospective cross-sectional study of 112 men with non-obstructive azoospermia who underwent open testicular biopsy at a single centre between 2006 and 2019. Archived H&E-stained slides were digitised and re-evaluated. Morphological changes were classified into predefined categories at whole-biopsy and individual tubule level, enabling detailed characterisation of hypospermatogenesis and mixed atrophy. Mean seminiferous tubule diameter, lamina propria thickness and interstitial Leydig cell quantity were measured and compared between histological groups. Results Bilateral biopsies were obtained in 104/112 patients (92.9%), and 26.9% showed discordant histological patterns. Mature spermatozoa were present bilaterally in 43.8% and unilaterally in 7.7% of bilaterally biopsied patients. Hypospermatogenesis was the predominant pattern (42.9%), followed by normal spermatogenesis (19.6%), Sertoli cell-only syndrome (23.2%), maturation arrest (12.5%) and tubular hyalinisation (1.8%). Two-thirds of hypospermatogenesis biopsies had heterogeneous mixed patterns. Mixed atrophy, a non-spermatozoa-producing heterogeneous pattern, was subdivided into 10 clusters based on the relative proportions of tubular types. Greater spermatogenic impairment was associated with reduced tubule diameter, increased lamina propria thickness and Leydig cell hyperplasia. Conclusions Testicular biopsies in azoospermic men show marked intratesticular and intertesticular heterogeneity, and bilateral sampling reveals clinically relevant discordance in many patients. Simple quantitative morphometry complements qualitative assessment. A structured reporting template may standardise terminology, improve interobserver agreement and support evidence-based decisions in daily male infertility care.