Pure post-pubertal yolk sac tumor of the testis: An extremely rare and aggressive entity

Context: Pure post-pubertal yolk sac tumors (YSTs) are an extremely rare type of malignant germ cell tumor (GCT) that account for <1 % of testicular GCTs. Clinically, they are more aggressive compared to the more common pre-pubertal counterpart. The aim of this study is to analyze the clinical presentation, ancillary tests and clinical outcomes in addition to presenting a spectrum of histomorphological features, in a case series along with a literature review.Design: A retrospective review of 4 cases of pure post-pubertal YST of the testis was performed. Data collected for each patient included demographics, clinical presentation, serum markers, radiology and pathologic findings, treatment, and clinical outcomes.Results: All patients presented with a testicular mass with or without associated pain and elevated serum alphafeto protein. Mean age at presentation was 36 years (range 25-68 years). Two patients presented with metastatic disease at the time of diagnosis. Histologic patterns and features are as follows: germ cell neoplasia in-situ (n = 4), reticular/microcystic, solid, glandular, papillary, endometrioid, cystic, necrosis and angiolymphatic invasion (n = 3). Fluorescent in-situ hybridization test performed on Case 2, showed presence of isochromosome 12p and next generation sequencing showed gains of 12p. Case 1, 2 and 4 showed metastatic disease on follow-up. Conclusions: Diagnosis of pure post-pubertal YST remains challenging due to the variety of morphologic patterns often present in these tumors. Extensive sampling along with use of ancillary tests is the key for diagnosis. In this study, 75 % of cases had metastatic disease at or after the diagnosis confirming the aggressive nature of this rare entity.