The ductal network in the human testis and epididymis: What belongs to which?

The testes and epididymis are traversed by a system of tubules in which sperm cells are generated, matured, nourished, and transported. Among these are the efferent ductules, which connect the rete testis to the duct of the epididymis. In the Terminologia Anatomica (TA), the efferent ductules are assigned to the testicles, while numerous anatomy, pathology, and urology textbooks assign them to the epididymis. Developmentally, they are derivatives of the Wolffian duct; as is the epididymal duct, which unquestionably belongs to the epididymis. Allocation of the efferent ductules to the compartment of the epididymis has been established clinically. The precise identification of tissue components of the epididymis is essential for the prognostic assessment of testicular cancers. In primary germ cell tumors of the testis, tumor infiltration into the epididymis can influence the tumor stage and can be associated with a worse clinical prognosis than localized tumor disease. Thus, it is desirable to update the TA, assigning the efferent ductules to the epididymis.