A case of testicular seminoma in persistent Mullerian duct syndrome with transverse testicular ectopia

We present a rare case of testicular seminoma in persistent Mullerian duct syndrome (PMDS) with transverse testicular ectopia (TTE). A 42-year-old man noticed scrotal swelling a few weeks earlier and underwent magnetic resonance imaging (MRI) on suspicion of testicular tumor. MRI revealed a normal left testis on the left side of the left scrotum and a heterogeneous mass on the right side within the left scrotum. No right testis was found in the right scrotum. A blind-ending tubular structure with thickened wall showed a three-layer appearance on T2-weighted imaging and extended from the prostate through the left inguinal canal to the left scrotum. Findings during surgery suggested right testicular tumor associated with right TTE. The histopathological and immunohistochemical diagnoses of the testicular tumor and blind-ending tubular structure were seminoma and persistent Mullerian duct, respectively. Testicular tumor in PMDS with TTE is rare but may possess a characteristic appearance on imaging. Proper knowledge of these diseases will allow correct preoperative diagnosis.