History: 35 year old male with 2 week history of right sided scrotal swelling, persistent after a trial of antibiotics.

The differential in this case given the absence of change with antibiotic treatment and absence of symptoms of infection, includes neoplasms such as testicular seminoma, and non-seminomatous tumors such as embryonal cell (the type that Lance Armstrong was diagnosed with), yolk sac, teratoma, and choriocarcinoma. Stromal tumors are another possibility, including sertoli cell and leydig cell tumors. The final diagnosis was a testicular seminoma.
See a case of a Leydig cell tumor of the testicle here.