Testicular germ cell tumors: revisiting a series in light of the new WHO classification and AJCC staging systems, focusing on challenges for pathologists.

Testicular germ cell tumors (TGCTs) are strikingly heterogeneous, reflecting a complex tumor model, posing serious challenges for pathologists. Accurate classification and staging, according to most recent systems, is fundamental. We aimed to revise a series of consecutively diagnosed TGCTs (2005-2016) in light of the new World Health Organization (WHO) classification and American Joint Committee on Cancer (AJCC) staging systems, discussing dilemmas imposed to pathologists. All 164 patients' clinical files/histological slides were reviewed. Follow-up was last updated on November 2017. Statistical analysis was performed with SPSS (v24). P < 0.05 was considered significant. Non-seminomatous tumors (NSTs) showed more frequently cysts, necrosis, hemorrhage, lymphovascular invasion (LVI) and higher stage than seminomas (SEs) (P < .001, P = .015, P < .001, P = .001, P = .007). Embryonal carcinoma (EC), yolk sac tumor (YST) and teratoma (TE) were the most frequent components in mixed tumors (82.5%, 82.5% and 80.7%). SEs with "atypical features" showed more LVI, higher mitotic count and more extensive necrosis (P = .030, P < .001, P = .016). LVI and >50%EC component, but not rete testis invasion, were associated with higher stage (P < .001, P = .009). Regarding SEs, there was an association between tumor size and both stage (P = .004) and LVI (P < .001). Only four patients disclosed altered stage group when AJCC 8th Edition was employed. Disease recurrence/progression occurred in 5.4% of cases. In two cases, tumor components in metastasectomy specimens were not present in the primary TGCT. Overall survival at 5 years was 98.6%. TGCTs are challenging neoplasms, and pathologists and clinicians alike must be aware of recent updates in classification and staging for adequately tailoring treatment strategies.