Abstract
Testicular adrenal rest tumours (TART) are found in patients with congenital adrenal hyperplasia (CAH) with the severity of testicular infiltration linearly related to the degree of enzymatic defect and subsequent compliance with treatment. We report a highly unusual case of TART in an adult patient with CAH caused by 21-hydroxylase deficiency who had not engaged with health services over a 3-year period. Typical imaging features of TART include bilateral well-defined lesions adjacent to the rete testes. However, in this rare case, the follow-up imaging found that the entirety of the testicular parenchyma had been replaced with TART and the patient had gone on to develop an adrenal nodule. As these testicular tumours are commonly misdiagnosed as primary germ tumours and tend respond well to treatment with circadian or reverse glucocorticoids, it is essential for the radiologist to be aware of both the common and more unusual imaging features appearances of TART in patients with CAH in order to facilitate early diagnosis and thus timely initiation of treatment.