What is the most likely histologic diagnosis for a healthy male patient with a solid testicular mass, elevated LDH and AFP levels, and a suspicious ultrasound finding, after undergoing a right radical inguinal orchiectomy?

Nonseminomatous Germ Cell Tumor (NSGCT)

The most likely histologic diagnosis is nonseminomatous germ cell tumor (NSGCT), based on the markedly elevated AFP and LDH levels. 1, 2

Diagnostic Reasoning

Tumor Marker Interpretation

The markedly elevated alpha-fetoprotein (AFP) is the definitive discriminating marker that establishes this diagnosis:

• AFP is produced exclusively by nonseminomatous germ cell tumor cells and is never elevated in pure seminoma, making it 100% specific for distinguishing tumor type 2
• Any elevation of AFP above the normal range indicates the presence of nonseminomatous elements, even if histology appears to be "pure seminoma" 1, 2
• The National Comprehensive Cancer Network explicitly states that if AFP is positive, the patient must be managed as having nonseminoma 1

Supporting Clinical Features

Additional findings that support NSGCT diagnosis:

• Partially necrotic mass on ultrasound is more characteristic of aggressive nonseminomatous tumors, which tend to have areas of hemorrhage and necrosis 3
• Elevated LDH serves as an important prognostic factor and is commonly elevated in advanced disease 3
• The solid mass presentation is consistent with germ cell tumors in general 4

Why Other Options Are Incorrect

• Seminoma (not listed but implied): Pure seminomas are constantly AFP-negative; any AFP elevation rules out pure seminoma 2
• Leydig cell tumor (Option A): These sex cord-stromal tumors do not produce AFP or typically present with markedly elevated tumor markers 3
• Sertoli cell tumor (Option C): Another sex cord-stromal tumor that does not produce AFP 3
• Teratoma (Option D): While teratomas are a type of NSGCT, they typically do not produce AFP unless combined with yolk sac tumor elements; the term "nonseminomatous germ cell tumor" is the broader, more accurate diagnosis 3
• Testicular lymphoma (Option E): Does not produce AFP or present with elevated germ cell tumor markers 3

Critical Clinical Caveat

Minor AFP elevations (≤16 ng/mL) should be interpreted cautiously as they may represent false-positives or borderline elevations that don't necessarily indicate occult NSGCT 3, 5. However, the question states "markedly elevated" AFP, which definitively indicates nonseminomatous disease requiring treatment as NSGCT 1

Management Implications

This patient requires:

• Treatment with chemotherapy regimen for nonseminomatous disease (BEP protocol: Bleomycin/Etoposide/Cisplatin) 1
• Serial AFP monitoring (half-life 5-7 days) to confirm appropriate decline with treatment 1, 2
• Staging CT scans of chest, abdomen, and pelvis 1