Semen cyst, once you hear it, seems to be a long cyst of semen. In reality, it means that some middle-aged men can feel a round or oval lump on one or both sides of the epididymis or testicles, with a very smooth surface, clear borders, and a cystic feeling when touched, as if the testicles had grown an extra one. This is a seminal cyst, a kind of cyst containing spermatozoa in the testicle or epididymis area, and this disease is characterized by the presence of spermatozoa in the intracapsular fluid. The exact cause of this disease is not well understood, but may be related to partial obstruction of the vas deferens, infection, and sexual dysfunction (e.g., high libido, difficulty in ejaculation). The intracapsular fluid is clear, cloudy or cream-colored depending on the number of sperm contained, and inactive sperm and fatty vesicles can be seen on microscopic examination. The disease occurs mostly between the ages of 40 and 60, before the function of spermatogenesis begins in adolescence, or after the cessation of sperm production in the elderly. Most patients have no conscious symptoms, and about 10% to 20% of patients have testicular swelling and mild discomfort in the scrotum and inguinal region, with occasional post-coital pain. Small, asymptomatic seminal cysts do not need to be treated. Cystectomy is an effective method of treatment for this condition, i.e., through a scrotal incision, revealing, freeing the cyst, clamping the narrow neck, removing it completely, and ligating the neck stump with intestinal thread. X-ray irradiation of the testes can inhibit the secretion of the testicular varicocele so that the cyst does not appear again and is suitable for the elderly or those who have children. The dose of radiation is 600-800 rads per 6-8 days. It does not affect sexual desire and occasionally testicular atrophy may occur. Sclerotherapy by puncture and fluid injection can be used for smaller cysts, but the recurrence rate is very high and it has the disadvantage of causing infection, so it is generally not used.