In testicular germ cell tumour with a retroperitoneal mass, is the retroperitoneal mass considered a primary tumour or a nodal metastasis?

Classification of Retroperitoneal Mass in Testicular Germ Cell Tumors

In testicular germ cell tumors with a retroperitoneal mass, the retroperitoneal mass is classified as nodal metastasis, not a primary tumor, unless there is no identifiable testicular primary tumor present. 1

Understanding the Classification Framework

The International Germ Cell Cancer Collaborative Group (IGCCCG) classification explicitly distinguishes between testicular primaries with retroperitoneal nodal disease versus true primary extragonadal retroperitoneal tumors. 1

When Retroperitoneal Mass is Nodal Metastasis

The retroperitoneal mass represents nodal metastasis when:

• A testicular primary tumor is identified (either clinically or pathologically) 1
• The retroperitoneal disease follows the typical lymphatic drainage pattern from the testis 1
• This is staged as clinical stage II (IIA: <2 cm nodes, IIB: 2-5 cm nodes, IIC: >5 cm nodes) 1
• The IGCCCG prognostic classification categorizes these patients as having "testis or primary extragonadal retroperitoneal tumour" in the good or intermediate prognosis groups, clearly separating testicular primaries with retroperitoneal spread from true retroperitoneal primaries 1

When Retroperitoneal Mass May Be Primary Tumor

The retroperitoneal mass is considered a primary extragonadal tumor only when:

• No testicular primary is identified on physical examination and ultrasound 1
• Testicular biopsy or orchiectomy shows either: (1) no tumor, (2) only intratubular germ cell neoplasia (TIN/CIS), or (3) "burned-out" scar tissue 1
• Biopsy of the retroperitoneal mass is required to confirm germ cell tumor histology before treatment 1

Critical Clinical Algorithm

Step 1: Evaluate the testis thoroughly 1

• Perform testicular ultrasound with 7.5 MHz transducer 1
• In patients presenting with retroperitoneal mass, approximately one-third will have TIN/CIS, one-third will show "burned-out" tumor (scar tissue), and only one-third have definitively primary extragonadal disease 1

Step 2: Determine tumor markers 1

• Elevated AFP or β-HCG supports germ cell tumor diagnosis 1
• If markers are normal and testicular examination is suspicious, biopsy the retroperitoneal mass before initiating treatment 1

Step 3: Apply correct staging and prognostic classification 1

• Testicular primary with retroperitoneal nodes = Stage II disease (nodal metastasis) 1
• True primary retroperitoneal GCT without testicular tumor = Primary extragonadal GCT 1
• This distinction is critical because primary retroperitoneal GCTs are included in good/intermediate prognosis groups, while primary mediastinal GCTs automatically confer poor prognosis 1

Prognostic Implications

The volume of retroperitoneal nodal disease significantly impacts prognosis and treatment decisions when it represents metastasis from a testicular primary. 1

• Stage IIA/B (nodal metastasis <5 cm): Volume and vascular invasion in the primary tumor are independent prognostic indicators for relapse 1
• Patients with low-volume nodal metastases (pN1) and normal pre-RPLND markers have only 15.6% relapse rate with observation alone 2
• Patients with elevated markers before retroperitoneal lymph node dissection have 80% relapse rate and require primary chemotherapy 2

Common Pitfall to Avoid

Do not assume all retroperitoneal masses in the setting of testicular GCT are metastatic. 1 Always perform thorough testicular evaluation including ultrasound, as approximately two-thirds of apparent "primary extragonadal" cases will actually have evidence of testicular origin (either active tumor, TIN, or burned-out lesion). 1 The distinction between nodal metastasis and primary extragonadal tumor fundamentally changes staging, prognostic classification, and treatment planning. 1