Lots of boys + men
Hydroceles are most common cause for scrotal sweeling in boys.
Collection of fluid. Resolves spontaeously by age one year in most infants unless huge. Beyond on year + if fluctuate in size or in adults need surgery to clear. Varicoceles + epididymal cysts are very common in post pubertal males. Testis torsion and epididimitis common + present as painful swellings which need treatment. Tumors rare.