It is normal to have some mild difference in testicular size, with the right testis being a little larger than the left.
A new lump or noticeable increase in the size of the testis should be looked into.
Lumps in the scrotum can come from the testis itself, or the epididymis which lies behind the testis.
Cysts arising from the epididymis are common and benign, and rarely require treatment.
A hydrocele is a collection of fluid in the layers around the testis, and cause a generalised swelling of the scrotum.
Varicoceles are swollen veins that drain the blood from the testis. These are similar to varicose veins of the legs except that they form in the scrotum. Large varicoceles can be felt in the scrotum, and can feel like a "bag of worms"
If the lump of swelling is associated with pain and tenderness, it may be caused by an infection of the testis and epididymis - epididymo-orchitis.
The most concerning cause of a lump in the scrotum or an enlarging testis is testicular cancer. While testicular cancer is rare, it is the most common cancer of boys and young men between 15-35yr old. However, lymphoma of the testis can similarly cause an enlarged testis in older men.
It is important to note that testicular cancer is usually painless - so one should not be misled by the absence of pain into thinking that the testicular lump is not an important issue.
Examination by a doctor is usually good enough to diagnose the above conditions. Ultrasound of the testis is sometimes needed to confirm the diagnosis.
