To further characterize the patterns of SOX9 expression in pre- and peri-pubertal testicular tissue, immunofluorescence staining against SOX9 and WT1 was performed in additional 28 testicular samples from the NORDFERTIL sample collection, including a wide range of primary diagnoses and treatment exposures (aged 6.9 ± 3.8 (mean ± SD) years, P12 to P39, Supplementary Table S1), and in 10 samples from the sample collection of the Pathology Department without known testicular disease (aged 5.5 ± 3.5 (mean ± SD) years, P40–P49, Supplementary Table S1). The gene discussed is SOX9; the disease is testicular disorder.