Metastatic Mixed Germ Cell Tumour Diagnosed on Cytology with an Occult Primary: A Case Report

Metastatic Germ Cell Tumours (GCTs) with occult primaries are rare presentations that pose significant diagnostic challenges, particularly on cytology. In the present case, a 27-year-old male presented with fever, abdominal pain, and weight loss, in whom ultrasound revealed para-aortic and inguinal lymphadenopathy without detectable testicular mass. Ultrasound-guided Fine-Needle Aspiration Cytology (FNAC) from para-aortic lymph nodes demonstrated highly atypical pleomorphic cells arranged in clusters and dispersed patterns, with high nuclear-to-cytoplasmic ratio, prominent nucleoli, multinucleation, and necrotic background, suggestive of metastatic high-grade malignancy with suspicion of GCT. Fluorodeoxyglucose Positron Emission Tomography– Computed Tomography (FDG PET-CT) showed metabolically active supraclavicular and abdominopelvic lymph nodes but no primary lesion. Excision of a supraclavicular lymph node revealed near-complete nodal replacement by tumour. Immunohistochemistry demonstrated positivity for SALL-4, CD30, and OCT3/4, with syncytiotrophoblastic cells positive for human Chorionic Gonadotropin (hCG) and Glypican-3, confirming metastatic mixed GCT comprising embryonal carcinoma and choriocarcinoma components. The patient received Bleomycin, Etoposide, and Cisplatin (BEP) chemotherapy and achieved remission but developed lung metastases after one year. This case highlights the diagnostic importance of FNAC in young males presenting with unexplained lymphadenopathy, even in the absence of an identifiable testicular mass. Mixed GCTs may mimic poorly differentiated carcinoma on cytology, and accurate diagnosis requires integration of morphology with immunohistochemistry and clinical-radiologic correlation. Early recognition is crucial, as metastatic GCTs remain potentially curable despite disseminated disease, and prompt therapy significantly impacts outcomes.