Recently Described and Clinically Important Entities in Testis Tumors: A Selective Review of Changes Incorporated Into the 2016 Classification of the World Health Organization.

Abstract

In 2016 the World Health Organization published a revised classification of testicular neoplasms based upon advances in understanding their pathogenesis and molecular biology. The rationale for this revision and additional clinically relevant observations were the topics of a talk given to the Houston Society of Clinical Pathologists in April 2017. This paper summarizes that talk. To summarize and explain the most important changes to the classification of testicular neoplasms in the World Health Organization 2016 revision. Peer-reviewed published literature and contributions by individuals with expertise in this area that were also reviewed by genitourinary pathologists. Most changes occurred in the germ cell tumor classification, including replacement of the terms <i>intratubular germ cell neoplasia unclassified</i> and <i>carcinoma in situ</i> by <i>germ cell neoplasia in situ</i>; subdivision of the tumors into 2 main categories, those derived from germ cell neoplasia in situ and those not derived from germ cell neoplasia in situ; distinction of germ cell neoplasia in situ from germ cells with delayed maturation and pre-germ cell neoplasia in situ; expansion of the trophoblastic tumor category to include epithelioid trophoblastic tumor and cystic trophoblastic tumor; and substitution of <i>spermatocytic tumor</i> for <i>spermatocytic seminoma</i> and its placement in the non-germ cell neoplasia in situ group. Other revisions included eliminating sclerosing Sertoli cell tumor as a distinct entity; the recognition of intratubular hyalinizing Sertoli cell tumor; and acceptance of the role of undifferentiated gonadal tissue in the pathogenesis of gonadoblastoma.