Prepubertal Screening for Testicular Adrenal Rest Tumors in Boys with Classic Congenital Adrenal Hyperplasia: Emerging Evidence and Practical Implications.

Testicular adrenal rest tumors (TARTs) are a frequent and clinically relevant complication of congenital adrenal hyperplasia (CAH), particularly its classic forms due to 21-hydroxylase deficiency. Although histologically benign, these masses develop within the rete testis and can progressively compress the seminiferous tubules, leading to fibrosis and, when longstanding, permanent gonadal injury and obstructive azoospermia; they are the foremost cause of impaired fertility in men with classic CAH. Their frequency increases with age, from approximately 25% in childhood to 46% in adulthood. This narrative review summarizes current evidence on the pathogenesis, predisposing factors and diagnostic work-up of TARTs, focusing on two practical questions: the appropriate age to begin monitoring and the imaging tools best suited to it. Sustained ACTH excess is regarded as the dominant growth-promoting signal, while the salt-wasting phenotype, severe CYP21A2 variants and inadequate disease control emerge as the principal predisposing factors. Although current guidelines advise ultrasound monitoring from adolescence, a growing body of pediatric data shows that TARTs can be detected well before puberty in patients at greatest risk. Scrotal ultrasonography remains the first-line technique, complemented by CEUS, elastography and MRI in selected cases. We outline a pragmatic, risk-adapted monitoring scheme and argue that earlier, childhood assessment in the highest-risk patients may help to safeguard future fertility, an approach that still awaits prospective confirmation.