Differential Diagnosis for a Lump on the Testicle

• Single most likely diagnosis
  • Epididymal cyst: This is a common and usually benign condition where a fluid-filled cyst forms on the epididymis, which is a tube at the back of the testicle that stores and carries sperm. It's often painless and can be felt as a lump.
• Other Likely diagnoses
  • Varicocele: An enlargement of the veins within the scrotum, similar to varicose veins. It's more common on the left side and can feel like a "bag of worms."
  • Hydrocele: A type of swelling in the scrotum that occurs when fluid builds up around a testicle, leading to the swelling of the scrotum.
  • Spermatocele: A benign cystic accumulation of sperm that arises from the head of the epididymis, which can be felt as a lump.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
  • Testicular cancer: Although less common, testicular cancer is a critical diagnosis not to miss. It often presents as a painless testicular lump or swelling.
  • Epididymitis: Inflammation of the epididymis, usually caused by infection. It can present with pain and swelling, which might be mistaken for a lump.
  • Testicular torsion: A medical emergency where the spermatic cord becomes twisted, cutting off the blood supply to the testicle. It's extremely painful and requires immediate attention.
• Rare diagnoses
  • Adrenal rest tumors: Rare, benign tumors that can occur in the testicles, associated with congenital adrenal hyperplasia.
  • Lipoma of the spermatic cord: A rare, benign tumor composed of fat tissue that can occur in the spermatic cord.
  • Cystic dysplasia of the testis: A rare congenital anomaly where the testis is replaced by multiple cysts, which can be felt as a lump.