A comparative study of PD-L1 immunohistochemical assays with four reliable antibodies in thymic carcinoma
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Tadashi Sakane1,*, Takayuki Murase2,*, Katsuhiro Okuda1, Hisashi Takino2, Ayako Masaki2, Risa Oda1, Takuya Watanabe1, Osamu Kawano1, Hiroshi Haneda1, Satoru Moriyama1, Yushi Saito3, Takeshi Yamada4, Ryoichi Nakanishi1 and Hiroshi Inagaki2
1Department of Oncology, Immunology and Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
2Department of Pathology and Molecular Diagnostics, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
3Department of Chest Surgery, Toyota Memorial Hospital, Toyota 471-8513, Japan
4Department of Thoracic Surgery, Kariya Toyota General Hospital, Kariya 448-8505, Japan
*These authors contributed equally to this work
Katsuhiro Okuda, email: email@example.com
Keywords: programmed death 1 (PD-1); programmed death ligand 1 (PD-L1); thymic carcinoma; squamous cell carcinoma; immunohistochemistry
Received: September 15, 2017 Accepted: January 02, 2018 Published: January 08, 2018
Currently, four immunohistochemical assays are registered with the US Food and Drug Administration to detect the expression of PD-L1. We investigated the PD-L1 expression in thymic carcinomas using these four diagnostic assays. The cases of 53 patients were reviewed and their specimens were subjected to four PD-L1 assays with different antibodies (SP142, SP263, 22C3, and 28-8). The PD-L1 expression in tumor cells (TCs) and immune cells (ICs) was evaluated. In TCs, the four assays showed similar scores in each case. Histopathologically, high TC scores were observed in squamous cell carcinomas (SqCCs). Meanwhile, there were no significant relationships among the IC scores in the four assays. In SqCCs, the high expression of PD-L1 (defined as ≥50% TC score) in TCs tended to be associated with early stage cancer. The patients with high expression levels of PD-L1 tended to show longer overall survival in the 22C3 assays (p=0.0200). In thymic carcinomas, the staining pattern showed high concordance among the four assays when TCs – rather than ICs – were stained. High PD-L1 positivity in TCs, especially in SqCCs, indicated that PD-1/PD-L1 targeted therapy may be a promising therapeutic approach.
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