Yolk Sac Tumor : Differential Diagnosis

Metastatic Hepatocellular Carcinoma (HCC) to the Ovary: YST with hepatoid morphology can mimic metastatic HCC, especially the fibrolamellar variety that is more common in younger females. Both YST and HCC are positive for glypican-3 and AFP; HCC is positive for HepPar-1 and shows membranous and pericanalicular staining with polyclonal CEA. SALL4 is negative in HCC and diffusely positive in YST. Metastatic Hepatoid Carcinoma: Hepatoid carcinoma is a rare and highly aggressive malignancy that can be seen in stomach, ovary, lung, pancreas, gall bladder, and uterus. It is positive for AFP and sometimes for SALL4 and glypican-3. However, it is also immunoreactive for EMA and CK7, unlike YST which is negative for both markers. Both metastatic hepatocellular as well as hepatoid carcinomas would present with bilateral ovarian involvement. Embryonal Carcinoma (EC): YST with a prominent glandular or papillary component can resemble EC. EC is more pleomorphic and positive for OCT4 whereas YST is negative. CD30 is of limited use in the differential since many cases of YST are also positive.