Its role varies: in cutaneous T-cell lymphoma (CTCL), a pro-IL-16 mutation reduces p27KIP1, enhancing cell growth; in multiple myeloma (MM), IL-16 overexpression drives plasma cell proliferation; and in breast cancer, it recruits pro-tumor macrophages [43,50]. The gene discussed is IL16; the disease is primary cutaneous T-cell non-Hodgkin lymphoma.