Lentinan is a polysaccharide extracted from the shiitake mushroom (Lentinula edodes) and has been investigated for its immunomodulatory and anti-tumor properties. Its use in leukemia is supported by some preclinical and limited clinical evidence, though it is not a standard treatment. Lentinan has demonstrated the ability to enhance host immune responses, particularly by stimulating macrophages, T lymphocytes, and natural killer (NK) cells, which may contribute to anti-tumor activity. Several in vitro studies have shown that lentinan can inhibit the proliferation of leukemia cell lines and induce apoptosis. Animal studies also suggest that lentinan can slow leukemia progression and improve survival when used as an adjunct to chemotherapy.

In human clinical settings, most research on lentinan has focused on solid tumors (such as gastric and colorectal cancers), where it is sometimes used as an adjuvant therapy in Japan and China. Reports specific to leukemia are less robust, typically limited to small-scale studies or case reports, and results are inconclusive. Major hematology guidelines do not currently endorse lentinan as a primary or adjunctive treatment for leukemia. Overall, while there is some scientific rationale and early-stage evidence supporting the immunostimulatory effects of lentinan, high-quality clinical trials in leukemia patients are lacking, and thus its use remains investigational.