CD44 and ovarian cancer: Although no remarkable differences of the overall mean CD44 immunostaining scores were observed between patient-matched metastasis and recurrent ovarian cancer tumors, the expression level of CD44 was lower in primary ovarian cancer tissue than in synchronous metastasis and recurrence, with a significant difference of approximately 0.6 in staining intensity (P value of metastatic vs. primary = 0.034; P value of recurrent vs. primary = 0.037; Figure 1 Panel A).