The white underside of the mushroom Artist Conk (Ganoderma applanatum) turns brown when bruised and can be intricately etched into detailed carvings, hence the English common name of this ubiquitous American tree fungus.
Artist Conks can live for 50 years and grow to arms width or more. David Arora of the mushroom identification guide Mushrooms Demystified says that along with the Red-belted Conk (Fomitopsis pinicola), Artist Conk is "the most common conk in our area [USA]." 
Ganoderma applanatum (Artist Conk) grows on nearly all species of hardwood, and even on some conifers such as Douglas Fir. "The only regions where it seems to be absent are those where there aren't any trees!" says Arora. 
In the past, people would burn Artist Conk to give off an insect repellant smoke as well as an odor that was also pleasant to humans. 
In 2008, a study by Jeong et al. stated that an isolated compound from Artist Conk "significantly inhibited the growth of solid tumor [Sarcoma-180] and increased the natural killer (NK) cell activity."  NK cells, or Natural Killer cells, are white blood cells that form a vital part in the human immune system's cancer fighting arsenal. At least four additional studies have also reported positive findings in regards to the anti-tumor properties of Ganoderma applanatum. [402, 403, 404, 405]
A less commonly studied area when it comes to medicinal mushrooms is their effect on blood glucose levels and diabetic complications. Jung et al. in 2005 reported that an alcohol extract of Artist Conk showed blood glucose lowering properties.  This was later confirmed in 2007 when a new study reported an average 22.0% blood glucose lowering effect by a compound isolated from Ganoderma applanatum, as well as a lowering of blood lipids (triglycerides and cholesterol) by 20.3%. 
However, the main purpose of the 2005 study by Jung was to assess Artist Conk's effect on inhibiting aldose reductase, an enzyme that's considered responsible for the organ complications seen in diabetics. It is commonly believed that inhibiting aldose reductase in diabetics could have a major effect on decreasing side-effects of diabetes. Jung reports that "these results suggested that G. applanatum [Artist Conk] might possess constituents with anti-diabetic and inhibitory effects on diabetic complications."  Two other studies have also found Artist Conk exhibiting significant aldose reductase inhibiting properties. [408, 409]
Looking at other research on Artist Conk, a 2005 study reported a polysaccharide extract of Artist Conk as strengthening the gastric mucosa barrier, useful in cases gastric ulcers.  Other papers have reported Artist Conk extracts as anti-viral,  anti-bacterial, [411, 412, 413] anti-parasitic and diuretic,  antioxidant,  and immune boosting. 
In his book Mycelium Running, medicinal mushroom expert Paul Stamets also lists inflammation and respiratory conditions as areas where research has shown Artist Conk extract to have a beneficial effect. 
Note: The statements on this page have not been evaluated by the Food and Drug Administration. This article is not intended to diagnose, treat, cure or prevent any disease. Never use any herb (or mushroom) except as advised by a licensed medical practitioner.