Late Recurrence of Non-Seminomatous Germ Cell Tumor via Somatic Transformation to Adenocarcinoma: A 30-Year Diagnostic Challenge

ImportanceLate recurrence (>2 years) of germ cell tumors (GCT) is rare, with this case being one of the longest late recurrences reported in literature. Case PresentationA 53-year-old male presented with a pelvic mass 30 years after initial treatment for testicular cancer.While initial pathology and elevated carcinoembryonic antigen (CEA) suggested a colorectal primary, fluorescence in situ hybridization (FISH) for isochromosome 12p confirmed somatic transformation of a GCT. ConclusionsThis case highlights the necessity of maintaining suspicion for GCT recurrence regardless of the latency period and underscores the utility of cytogenetic testing in discordant diagnostic presentations.