Diagnostic Utility of SALL4 in Primary Germ Cell Tumors of the Central Nervous System: a Study of 77 Cases

Primary germ cell tumors of the central nervous system (CNS) sometimes pose diagnostic difficulty. In this study we analyzed the diagnostic utility of a novel marker, SALL4, in 77 such tumors (59 pure and 18 mixed) consisting of the following tumors/tumor components: 49 germinomas, 7 embryonal carcinomas, 27 yolk sac tumors, 3 choriocarcinomas, and 14 teratomas. We also stained SALL4 in 99 primary non-germ cell tumors to test SALL4 specificity. We compared SALL4 with OCT4 in all germ cell tumors and compared SALL4 with alpha-fetoprotein and glypican-3 in all yolk sac tumors. The staining was semiquantitatively scored as 0 (no staining), 1+ (<or=30%), 2+(31-60%), 3+ (61-90%), and 4+ (>90%). Strong SALL4 staining was observed in all 49 germinomas (4+ in 48, 3+ in 1), 7 embryonal carcinomas (all 4+), and 27 yolk sac tumors (1+ in 1, 2+ in 2, 3+ in 7, 4+ in 17). SALL4 staining, 1+ weak to focally strong, was observed in 2 of 3 choriocarcinomas (in mononucleated trophoblasts) and in 9 of 14 teratomas (in primitive neuroepithelium and teratomatous glands). All germinomas and embryonal carcinomas showed strong OCT4 staining (4+ in all except 1 germinoma with 3+), whereas other germ cell tumors were negative. Out of 27 yolk sac tumors, 26 showed positive alpha-fetoprotein staining (1+ in 9, 2+ in 7, 3+ in 5, and 4+ in 5). All yolk sac tumors showed positive glypican-3 staining (1+ in 6, 2+ in 6, 3+ in 7, and 4+ in 8). The mean percentage of yolk sac tumor cells stained was 84% with SALL4, 45% with alpha-fetoprotein, and 63% with glypican-3 (P<0.01). No non-germ cell tumors showed SALL4 staining. Our results indicate that SALL4 is a novel sensitive diagnostic marker for primary germ cell tumors of the CNS with high specificity. SALL4 is a more sensitive marker than alpha-fetoprotein and glypican-3 for yolk sac tumors.