An introduction to the WHO 5th edition 2022 classification of testicular tumours

Abstract

The 5th edition of the World Health Organisation Blue Book was published recently and includes a comprehensive update on testicular tumours. This builds upon the work of the 4th edition, retaining its structure and main nomenclature, including the use of the term ‘germ cell neoplasia in situ’ (GCNIS) for the pre‐invasive lesion of most germ cell tumours and division from those not derived from GCNIS. While there have been important developments in understanding the molecular underpinnings of testicular cancer, this updated classification paradigm and approach remains rooted in morphology. Nomenclature changes include replacement of the term ‘primitive neuroectodermal tumour’ by ‘embryonic neuroectodermal tumour’ based on the non‐specificity of the former term and to separate these tumours clearly from Ewing sarcoma. Seminoma is placed in a germinoma family of tumours emphasising relation to those tumours at other sites. Criteria for the diagnosis of ‘teratoma with somatic transformation’ have been modified to not include variable field size assessments. The word ‘carcinoid’ has been changed to ‘neuroendocrine tumour’, with most examples in the testis now classified as ‘prepubertal type testicular neuroendocrine tumour’. For sex cord‐stromal tumours, the use of mitotic counts per high‐power field has been changed to per mm2 for malignancy assessments, and the new entities, ‘signet ring stromal tumour’ and ‘myoid gonadal stromal tumour’, are defined. Well‐differentiated papillary mesothelial tumour has now been defined as tumour type with a favourable prognosis. Sertoliform cystadenoma has been removed as an entity from testicular adnexal tumours and placed with Sertoli cell tumours.

What's new in WHO fifth edition – urinary tract

“…We have tried to avoid redundancy with other papers dealing with the new WHO classification, therefore some sections are brief. 3…”

“…In order to accommodate these changes, the newest classification shows several important refinements which we summarise here. We have tried to avoid redundancy with other papers dealing with the new WHO classification, therefore some sections are brief 3 …”

Age‐incidence patterns of seminoma and nonseminoma among males and females in Germany and the United States, 2008–2016

“…1,2 The 5th edition of the WHO classification of testicular tumors introduces the term germinoma to replace seminoma and nongerminoma to replace nonseminoma for all anatomical localizations. 3 In contrast to the changes in the classification of TGCTs, the most recent classification of ovarian tumors in 2020(5 th edition) did not include marked changes in classification and was based only on morphological features. 4 Ovarian cancers can arise from epithelial, germ cell, or stromal cells although approximately 90% originate from the epithelium.…”

“…germ cell neoplasia in situ (GCNIS) associated GCT versus GCNIS‐unrelated GCT), and some reclassifications of morphologies (expansion of the non‐choriocarcinomatous trophoblastic tumor group, renaming of spermatocytic seminoma to spermatocytic tumor) among others 1,2 . The 5th edition of the WHO classification of testicular tumors introduces the term germinoma to replace seminoma and nongerminoma to replace nonseminoma for all anatomical localizations 3 …”

“…A diagnostic problem inherent with the morphologic classifications of TGCT and OGCT presented above, is that teratomas with similar histology can be benign or malignant. The WHO classification of TGCTs has partly addressed this problem by distinguishing between prepubertal‐type (type I) teratomas, which are benign, and postpubertal‐type (type II) teratomas, which are malignant 2,3 . This is feasible for TGCTs because all GCTs that arise in boys under the age of six years are type I.…”