AbstractObjectiveExplored the correlation between CD1a expression in recurrence and prognosis of ovarian cancer (OV).MethodsThe CD1a expression profile in OV, recurrent OV, and normal tissues, as well as corresponding clinical data, were obtained from The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC), Gene Expression Omnibus (GEO), and Genotype Tissue Expression (GTEx) databases. Meanwhile, immunohistochemical detection of CD1a expression in normal and OV tissues. Kaplan–Meier curves were plotted to estimate the hazard ratio (HR) of survival in OV. In addition, the correlation between CD1a and immune cells in OV, as well as the CD1a expression profile and corresponding survival time in pan‐cancer were obtained from TCGA database.ResultsCD1a was overexpressed in OV and was significantly under‐expressed in recurrent OV (TCGA‐OV, p < 0.0001 and ICGC‐OV, p < 0.0001). CD1a immunohistochemistry is significantly overexpressed in OV compared to normal tissue (p < 0.05). Recurrent OV (ICGC, p < 0.001; GSE17260, p < 0.001; GSE32062, p < 0.05). The prognosis in OV was significantly better when CD1a is overexpressed compared to under‐expressed (HR [low], 1.426: 95% confidence interval [CI], 0.912–2.128; p = 0.050). Meanwhile, the overexpression of CD1a has a better prognosis than low expression in OV and recurrent OV (p = 0.004, HR [low] = 2.462, 95%CI [1.346–4.504] and p = 0.011, HR [low] = 2.199, 95%CI [1.202–4.024]). In addition, CD1a expression was closely correlated with immune cells, the CD8+ T cells, macrophages, and NK cells, while uncharacterized cells were significantly different (p = 2.65e−6, p = 7.52e−13, p = 8.28e−12, and p = 5.89e−8, respectively). Moreover, CD1a expression affected the prognosis in various other cancers.ConclusionsCD1a expression affected the recurrence and prognosis of OV and is closely related to various immune cell levels.