Final answer:
The two scrotal masses that can trans-illuminate are a hydrocele and a spermatocele, both are fluid-filled and allow light to pass through during the examination.
Step-by-step explanation:
The two scrotal masses that can trans-illuminate are a hydrocele and a spermatocele. Trans-illumination is a diagnostic technique in which a light source is placed against the scrotum to see if the mass inside is solid or filled with fluid. Solid masses such as tumors will not let light pass through, whereas fluid-filled structures like hydroceles and spermatoceles will allow light to pass, showing a red or pink glow.
A hydrocele is an accumulation of serous fluid within the tunica vaginalis, a serous membrane that surrounds the testis. It may be congenital or acquired and is often painless. A spermatocele, on the other hand, is a cyst that develops in the epididymis and is generally filled with dead sperm cells and fluid.
It's important to differentiate these masses from other pathologies such as testicular tumors, which are solid and would not trans-illuminate. A careful physical examination, sometimes accompanied by ultrasound if the diagnosis is unclear, is essential for proper identification and treatment of scrotal masses.