[Importance of pathology for therapy planning of testicular germ cell tumors]

Testicular tumors can be divided into germ cell tumors and sex cord stromal tumors. Malignant testicular germ cell tumors (TGCT) represent about 90-95 % of all testicular tumors and are the most common solid neoplasms in young men aged 20-40 years with an increasing incidence in industrialized countries. Treatment of TGCT is performed by an individual and risk-adapted approach taking primary tumor histology, histopathlogical and molecular prognostic risk factors, tumor stage and for metastasized tumors the response to systemic chemotherapy into consideration. Knowledge of the specific histopathology of the primary tumor and the prognostic factors is of utmost importance for the treating urologist and oncologist in order to avoid undertreatment or overtreatment. Established risk factors which have been validated in retrospective and prospective studies for clinical stage I non-seminomatous TGCT are the presence of vascular invasion and the percentage of embryonal carcinoma. In clinical stage I seminomas tumor size (> 4 cm) and presence of rete testis infiltration have been identified as risk factors in retrospective but not in prospective studies. Quantitative histopathology of the primary tumor is also important for the management of small residual masses following chemotherapy: if the masses are ≤ 1 cm, postchemotherapy retroperitoneal lymph node dissection is only indicated if the primary tumor contains ≥ 50 % teratoma. Quantitative pathohistology of the resected residual masses is of importance for the decision-making process of a consolidating chemotherapy which is only of benefit if the amount of vital cancer tissue is > 10 %. Resection of residual hepatic and thoracic masses is indispensable. For gonadal stromal tumors knowledge of atypical nuclear forms, increased rate of mitosis and increased growth fractions are important for therapy planning.