Brachyury expression is highly specific for chordoma: A tissue microarray study involving 14,976 cancers from 135 different tumor types and subtypes

Brachyury protein plays a role in defining the midline of bilaterian organisms. Commonly expressed in chordomas, brachyury immunohistochemistry is used to distinguish chordomas from their differential diagnoses. However, brachyury expression has also been described to frequently occur in other cancer entities. To better comprehend the role of brachyury expression in cancer, a tissue microarray containing 14,976 samples from 135 different tumor entities and 608 samples of 76 different normal tissue types were analyzed by immunohistochemistry. Brachyury staining was found in 55 (0.44 %) of the 12,409 interpretable tumor samples, including 37 (0.3 %) with weak, 10 (0.08 %) with moderate, and 8 (0.06 %) with strong positivity. Brachyury staining strongly predominated in chordomas. Of ten chordomas, 7 were strongly and 3 moderately positive. Only 5 of the 134 analyzed further tumor categories showed brachyury staining, 4 of which originated from testicular germ cells. Brachyury positivity occurred in 21.4 % of 42 yolk sac tumors, 15.2 % of 46 embryonal carcinomas, 4.4 % of 562 seminomas, and 2.4 % of 41 teratomas of the testis. Our data support the previously suggested high specificity of brachyury for chordoma detection, and demonstrate that germ cell tumors represent the only additional group of unrelated cancer entities expressing brachyury at a significant level.