PIK3R1 and B-cell non-Hodgkin lymphoma: The PI3Kδ enzyme complex, including PIK3CD, PIK3R1, or phosphatase and tensin homolog (PTEN), is primarily present in the immune system and comprises a catalytic (p110δ) and regulatory (p85α) subunit, and both overactivation and underactivation of PI3Kδ lead to impaired and dysregulated immunity, for instance, B-cell lymphomas [20, 21].