A sperm granuloma is a small mass or lump that may develop following a vasectomy. This lump is an inflammation created by extravasated sperm which leaks or is forced out of the cut end of the vas deferens during surgery. These granulomas can vary in size and are usually about the size of a pea. They can be encapsulated in a lump of scar tissue. Sperm granulomas are not life-threatening or cancerous. They do not cause any harm but may cause pain and discomfort in some cases. If no pain or discomfort, not to worry