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).