What is the malignant potential of small (<2 cm), nonpalpable testicular incidentalomas in adults? A systematic review

Context: Unlike palpable lumps, a large number of nonpalpable testicular lesions found incidentally at ultrasound in asymptomatic postpuberal males are either benign tumours or non-neoplastic lesions. The prevalence of malignancy, however, is appraised based on small case series. Dedicated studies report a large number of patients, and systematic review articles are lacking. Objective: This systematic review is aimed to assess, from the analysis of the pooled data of the available literature, the incidence of benign tumours, malignant tumours, and non-neoplastic lesions, and to identify predictive characteristics for malignancy. Evidence acquisition: A systematic review of PubMed, Scopus, Google Scholar, Turning Research Into Practice (TRIP) database, and the Cochrane Library was conducted on January 6, 2022, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Studies were retrieved reporting on adult asymptomatic men, with single, incidentally identified small testicular lesions, either fertile or infertile, with negative tumour markers and without specific risk factors for malignancy. Lesions ≤20 mm were considered small. Seventy-four studies were selected for inclusion in this analysis. Twenty-six additional publications have been retrieved by the bibliography quoted in the selected articles. Evidence synthesis: Pooled data of 1348 lesions in 1348 patients were collected. Of these lesions, 408 could be retrieved individually, 44.6% were benign, 27.2% were malignant, and 20.8% were non-neoplastic. Virtually all lesions &lt;3 mm and 86.6% of lesions &lt;5 mm were benign. Lesions &gt;10 mm have a 38.14% probability of being benign. Hyperechoic lesions are likely benign. Fertility status does not affect the risk of malignancy. Conclusions: Very small (&lt;3 mm) and small (&lt;5 mm) incidentally detected testicular lesions in asymptomatic postpuberal men with normal tumour markers could be frequently benign. More prospective studies are needed to better support this finding. Management strategies should be developed for these patients to reduce overtreatment. Patient summary: Small testicular lesions are incidentally founded at ultrasound. It is not easy to distinguish a benign lesion from a malignant one. Results of this study are reporting a higher incidence of benign lesions with a diameter of &lt;5 mm. More studies are needed to better understand the biology and the management strategy for small testicular lesions.