Combined yolk sac tumor and adenocarcinoma in a gastric stump: molecular evidence of clonality

BACKGROUND: Extragonadal yolk sac tumors of the gastrointestinal tract are extremely rare neoplasms. Their greater rarity compared with other extragonadal yolk sac tumors suggests that different pathogenetic mechanisms could be involved according to the site of origin. This report describes a case of a combined yolk sac tumor and adenocarcinoma that arose in a gastric stump in a man age 61 years 43 years after he underwent distal gastric resection and gastrojejunostomy (Billroth II operation) for a benign duodenal ulcer. The coexistence of an adenocarcinomatous component with the yolk sac component suggests that the two histologic patterns may represent distinct phenotypes arising from a common mucosal epithelial cell. METHODS: Immunohistochemical and molecular techniques were used to define the mutation pattern of p53 in both components of the tumor. RESULTS: Single-strand conformation polymorphism and sequencing analyses demonstrated the same pattern of p53 mutation in the adenocarcinomatous and yolk sac tumor components. CONCLUSIONS: This finding suggests that the two tumors could have been derived from the same cellular clone and supports the hypothesis that the two components represented a heterogeneous differentiation of the same tumor.