RNA-binding protein LIN28 is a marker for testicular germ cell tumors.

LIN28 is an RNA-binding protein involved in maintaining the pluripotency of embryonic stem cells. Using formalin-fixed, paraffin-embedded tissue blocks, we performed immunohistochemical staining of LIN28 in 103 primary and 81 metastatic testicular germ cell tumors (54 intratubular germ cell neoplasias, unclassified type; 49 primary and 20 metastatic classic seminomas; 35 primary and 24 metastatic embryonal carcinomas; 35 primary and 15 metastatic yolk sac tumors; 23 primary and 12 metastatic teratomas; 6 primary and 10 metastatic choriocarcinomas; and 5 spermatocytic seminomas). The percentage of tumor cell stained was scored as 0 (0%), 1+ (≤30%), 2+ (31%-60%), 3+ (61%-90%), and 4+ (>90%). We stained LIN28 in 327 non-germ cell tumors to determine its specificity. We also compared LIN28 with SALL4 (Sal-like 4) and OCT4 (octamer-binding transcription factor 4) in all germ cell tumors. The staining was cytoplasmic for LIN28 and nuclear for SALL4 and OCT4. Strong 4+ LIN28 staining was seen in all 54 intratubular germ cell neoplasias, 59 embryonal carcinomas, and 50 yolk sac tumors. Positive LIN28 staining was seen in all 69 classic seminomas (1+ in 3, 3+ in 3, and 4+ in 63) (63, strong). Variable staining of LIN28 was seen in 10 of 35 teratomas (1+ to 3+, weak to strong intensity), 12 of 16 choriocarcinomas (1+ to 4+, weak to strong intensity), and 1 of 5 spermatocytic seminomas (2+, weak). Only 10 of 327 non-germ cell tumors showed 1+ weak LIN28 staining. Therefore, LIN28 is a highly sensitive marker for testicular intratubular germ cell neoplasias, classic seminomas, embryonal carcinomas, and yolk sac tumors with relatively high specificity. LIN28 can be used as a diagnostic marker for these tumors and has demonstrated a similar level of diagnostic utility as SALL4 (except for a few classic seminomas), although it does not show an advantage over SALL4. The major advantage of LIN28 over OCT4 is in diagnosing yolk sac tumors (yolk sac tumors negative for OCT4).

RNA-binding protein LIN28 is a marker for primary extragonadal germ cell tumors: an immunohistochemical study of 131 cases.

LIN28 has been shown to have an important role in primordial germ cell development and malignant transformation of germ cells in mouse. In this study, we examined the immunohistochemical profile of LIN28 in 131 primary human extragonadal germ cell tumors (central nervous system (CNS) 76, mediastinum 17, sacrococcygeal region 30, pelvis 3, vagina 2, liver 1, omentum 1, and retroperitoneum 1), including the following tumors and/or components: 57 seminomas/germinomas, 10 embryonal carcinomas, 74 yolk sac tumors, 6 choriocarcinomas, 15 mature, and 13 immature teratomas. We compared LIN28 with SALL4 to assess its diagnostic value. To determine its specificity, we examined LIN28 in 406 extragonadal-non-germ cell tumors (103 carcinomas, 91 sarcomas, 9 melanomas, 12 mesotheliomas, 83 lymphomas, 9 plasmacytomas, 82 CNS tumors, and 17 thymic epithelial tumors). The staining was semi-quantitatively scored as 0 (no cell stained), 1+ (0-30%), 2+ (31-60%), 3+ (61-90%), and 4+ (>90%). LIN28 staining was seen in all seminomas/germinomas (3+ in 1 and 4+ in 56), embryonal carcinomas (4+ in all 10), and yolk sac tumors (3+ in 3 and 4+ in 71). Variable LIN28 staining was seen in 5 of 6 choriocarcinomas (1+ to 4+), 8 of 13 immature teratomas (1+ to 2+ in immature elements), and in 1 of 15 mature teratomas (1+). Only 11 of 406 non-germ cell tumors showed 1+ LIN28 staining. Therefore, LIN28 is a sensitive (100% sensitivity) marker for primary extragonadal seminomas/germinomas, embryonal carcinomas, and yolk sac tumors with high specificity. Compared with SALL4, LIN28 demonstrated a similar level of diagnostic sensitivity for seminomas/germinomas and embryonal carcinomas. For primary extragonadal yolk sac tumors, although SALL4 stained all tumors (1+ in 1, 2+ in 2, 3+ in 10, and 4+ in 61), LIN28 stained more tumor cells (mean 95 vs 90%, P = 0.03) and was therefore more sensitive. For primary extragonadal yolk sac tumors, combining LIN28 and SALL4 can achieve a higher diagnostic sensitivity than either alone.