Yolk sac tumor with a prominent polyvesicular vitelline pattern: a report of three cases.

We report 3 cases of the rare polyvesicular vitelline variant of ovarian yolk sac tumor (YST). The patients were 23, 29, and 43 years old, and all presented with large unilateral adnexal masses confined to the ovary. One tumor was predominantly cystic, and the other 2 had prominent cystic components; all 3 also had solid components. Microscopic examination of the cystic regions showed dilated cysts that largely effaced the stroma resulting in a honeycomb-like appearance. The solid foci were characterized predominantly by small tubules in a fibrous stroma; the tubules exhibited variably conspicuous cystic dilatation to merge with the microcystic appearance. The tumor cells varied from large and primitive-appearing to flattened and deceptively innocuous when lining large cysts. They were immunoreactive for α-fetoprotein and glypican-3. Non-polyvesicular vitelline components of YST were present focally in 2 cases (hepatoid in one, reticular and endometrioid like in the second). Two patients are disease free after 20 and 26 years, respectively; disease-free follow-up is of short duration in the third case (2 years). The good long-term outcome in 2 cases supports prior evidence that suggests that the natural history of this form of YST may be more indolent than conventional forms of the tumor.