Consequently, we postulated that MZ B cells not only act in an anti-tumoral capacity by secreting IgM short- to mid-term but also regulate possibly significantly pro-tumoral processes due to their strong immunosuppressive potential, as evidenced by CD39+CD73+ co-expression, particularly pronounced in tumor-bearing mice’s splenic tissue, cervical lymph nodes, and tumor tissue. This evidence concerns the gene NT5E and neoplasm.