Mesima, also known as Phellinus linteus, is a medicinal mushroom traditionally used in East Asian herbal medicine. In traditional Chinese medicine (TCM), Mesima is believed to "support the Spleen" by enhancing vitality, improving digestion, and strengthening the body’s resistance to illness. The concept of the "Spleen" in TCM encompasses functions such as nutrient absorption, energy production, and immune support, rather than strictly referring to the anatomical organ.

Historical texts and herbal compendia describe Mesima as being used to treat conditions like poor appetite, weakness, and fatigue—symptoms associated with Spleen Qi deficiency in TCM theory. These uses are primarily based on centuries of empirical practice and the mushroom’s inclusion in multi-herb formulations designed to bolster the Spleen and overall health.

Modern scientific research on Mesima has focused mainly on its potential immunomodulatory and anti-cancer properties, with studies demonstrating effects such as stimulating immune cell activity and inhibiting tumor growth in vitro and in animal models. However, direct scientific evidence for Mesima specifically supporting "Spleen function" as defined in TCM is limited. Most support for this application comes from traditional practice rather than rigorous clinical trials or mechanistic studies targeting the Spleen body system.