Final answer:
A hydrocele is a benign fluid-filled sac in the anterior testis. Sperm develop tails in the epididymis, and biopsies are important for diagnosing prostate and testicular cancer.
Step-by-step explanation:
The benign fluid-filled sac that develops in the anterior testis is known as a hydrocele. This type of swelling occurs when fluid accumulates in the thin sheath surrounding a testicle. Hydrocele is common in newborn males but can also occur at any age typically due to inflammation or injury within the scrotum. Regarding the development of sperm tails, this process occurs in an organ called the epididymis after they have been initially produced in the testes. Lastly, a biopsy is particularly important for the diagnosis of prostate cancer and testicular cancer.