CT83, a cancer/testis antigen, was detected in nearly half of 222 breast cancer tumors, and multivariable analysis showed its apparent links to aggressive features largely reflect enrichment in the triple-negative phenotype. CT83, a member of the cancer/testis antigen family, was detected in 48.2 percent of 222 breast cancer cases examined by immunohistochemistry, and its presence tracked closely with the triple-negative phenotype, according to a study published in Diagnostic Pathology.
Cancer/testis antigens are a group of proteins that are normally confined to immunologically privileged tissues, such as the testis, but become aberrantly expressed in a range of malignancies.
The new study set out to clarify the clinicopathologic significance of CT83 expression in breast cancer, to test whether it is associated with programmed cell death ligand-1 (PD-L1), a key immune checkpoint molecule, and to determine whether it relates to disease-free survival. The researchers performed immunohistochemistry on formalin-fixed, paraffin-embedded tissue from 222 patients with breast cancer. CT83 positivity was defined conservatively as an intensity score of at least 1, regardless of the percentage of stained cells, meaning that even low-level expression counted as positive.
Statistical associations were assessed using chi-square tests with false discovery rate correction, a method that guards against spurious findings when many comparisons are made, and by multivariable logistic regression that adjusted for triple-negative breast cancer status and histologic grade. Survival analysis was carried out with Kaplan-Meier and Cox methods in a stage I-III cohort of 213 patients.
The headline finding was that CT83 expression was associated with a cluster of aggressive clinicopathologic features: negative hormone receptor status, a high Ki-67 proliferation index, larger tumor size, higher histologic grade, and triple-negative breast cancer itself, all reaching statistical significance after false discovery rate adjustment. On its face, this pattern suggests that CT83 marks biologically aggressive disease.
However, the multivariable analysis told a more disciplined story. When the researchers adjusted for triple-negative status and histologic grade simultaneously, only triple-negative breast cancer status remained independently associated with CT83 positivity, with an adjusted odds ratio of 3.87 (95 percent confidence interval 1.56 to 9.60, p = 0.004). In other words, the apparent links between CT83 and features such as high grade or large tumor size appear to be largely secondary to the fact that both CT83 and those features are enriched in the triple-negative subtype, rather than representing independent relationships.
The PD-L1 story followed a similar arc. CT83 expression correlated with PD-L1 in tumor cells (Kendall’s tau = 0.190, p = 0.004) and in immune cells (tau = 0.194, p = 0.003) in unadjusted analyses. Yet neither correlation survived adjustment for triple-negative status and histologic grade, and neither remained significant when the analysis was restricted to the triple-negative subgroup alone, which comprised 36 patients. The authors interpret this as evidence of substantial confounding by the triple-negative phenotype: CT83 and PD-L1 are both more common in triple-negative tumors, so they co-occur without necessarily being biologically linked.
Perhaps the most consequential negative result concerned prognosis. CT83 expression was not associated with disease-free survival in the stage I-III cohort, with a hazard ratio of 0.79 (95 percent confidence interval 0.37 to 1.67, p = 0.533) and a log-rank p value of 0.532. Instead, lymphovascular invasion remained the only independent prognostic factor in the multivariable survival model, with an adjusted hazard ratio of 2.85 (95 percent confidence interval 1.34 to 6.08, p = 0.007). This finding underscores that, at least in this cohort, CT83 does not add prognostic information beyond established clinicopathologic variables.
The authors conclude that CT83 expression is enriched in the triple-negative phenotype, and that its associations with other aggressive clinicopathologic features are largely attributable to this shared enrichment rather than to independent biological relationships. They similarly caution that the correlation with PD-L1 should be interpreted cautiously, since it likewise appears to reflect shared triple-negative enrichment rather than a direct biological link. At the same time, they argue that CT83 warrants further investigation as a candidate biomarker reflecting the triple-negative phenotype and tumor aggressiveness.
Several caveats deserve emphasis. The study analyzed a single cohort of 222 patients, and the triple-negative subgroup analyzed for subgroup-specific correlations was small, at 36 patients, which limits statistical power for those specific tests. The survival analysis was confined to patients with stage I-III disease. The article is being shared early as a peer-reviewed, accepted version that remains subject to further editorial edits before the final version of record. Within those limits, the study offers a measured contribution: rather than establishing CT83 as an independent marker of aggression or immune activation in breast cancer, it clarifies that the protein’s observed associations largely mirror the triple-negative phenotype itself, a conclusion that should inform how future biomarker studies in this field are designed and interpreted.
Subject of Research: The clinicopathologic significance of CT83 expression in breast cancer and its relationship with triple-negative status, PD-L1 and survival
Article Title: CT83 expression is enriched in triple-negative breast cancer and is associated with aggressive clinicopathologic features
Article References: Kim, G., Hong, M., Park, S. T., Kim, H. S., Kim, S., & Ahn, S. (2026). CT83 expression is enriched in triple-negative breast cancer and is associated with aggressive clinicopathologic features. Diagnostic Pathology. https://doi.org/10.1186/s13000-026-01856-x
Image Credits: AI Generated
DOI: 10.1186/s13000-026-01856-x
Keywords: CT83, cancer/testis antigen, triple-negative breast cancer, PD-L1, immunohistochemistry, biomarker, disease-free survival, Ki-67, lymphovascular invasion, Diagnostic Pathology, tumor immunology, clinicopathology
News Source: Nathaniel Bowman. (October 28, 2026). CT83 Protein Marks Triple-Negative Breast Cancer, but Its Aggressive Links Prove Indirect. Scienmag.
