In 1999, the tree conk Hemlock Varnish Shelf was found to possess "the strongest antioxidant activity of five species of Ganoderma [Reishi] tested." It was found to have stronger antioxidative activity than Vitamin E. The abundance of antioxidants in Hemlock Varnish Shelf has been confirmed by several other research papers. [827, 828, 829, 830]
The fungus Hemlock Varnish Shelf (Ganoderma tsugae) is common on Eastern Hemlock trees (Tsuga canadensis) throughout the Appalachian mountain range. It is the local variety of Reishi (Ganoderma spp.) in the eastern United States.
And in fact it shares many medicinal attributes with the better known Common Reishi (Ganoderma lucidum), which has been used in Traditional Chinese Medicine for 2,000 years or more.
Although it can only be found in the east of the American continent, Hemlock Varnish Shelf can also be found in Southeast Asia on Asian hemlock trees. So it is not all that surprising that several Asian studies have been conducted specifically on Ganoderma tsugae.
The primary Asian source of Hemlock Varnish Shelf is commercially grown specimens from Taiwan that are exported to mainland China as medicinal mushrooms. The traditional use of Ganoderma tsugae in Chinese medicine is for the treatment of autoimmune conditions, asthma and other conditions involving inflammation.
The single modern study conducted on Hemlock Varnish Shelf extract to treat an autoimmune disease, conducted in 2001, concluded that it "improved the survival rate of lupus." 
A bit more research has been conducted on asthma and lung inflammation. In 2007, it was reported that Ganoderma tsugae extract produced "anti-inflammatory effects on airway responses"  in broncheoalveolar inflammation, including allergic asthma. [802, 803]
One of the most novel uses of Hemlock Varnish Shelf is as a skin substitute during wound healing. The skin substitute material, commercially sold as Sacchachitin, has been proven in numerous studies to promote and speed up skin healing. It has been observed that "rapid wound healing" takes place when covered by Sacchachitin as compared to regular gauze  - a "wound area covered by SACCHACHITIN completely healed by 21 days, while that covered with cotton gauze did not." [805, 806, 807]
Hemlock Varnish Shelf extract has also been tested for its antitumor properties with promising results. [808, 809, 810, 811, 812] In particular lung cancer [813, 814, 815] and breast cancer  have responded favorably in scientific research. It was also shown in one study to help prevent cancer metastasis. 
Same as with Common Reishi (Ganoderma lucidum), the Hemlock Reishi (or Hemlock Varnish Shelf) has also been shown to be a powerful immunomodulator. [817, 818, 819, 820, 821, 822, 823] What that means is that both of these species of Reishi will help adjust the immune system up or down, whichever is needed. They can help strengthen a weak immune system in one person,  while helping to calm an overactive immune system in another person, perhaps someone with an autoimmune disease or an inflammatory condition such as allergy, asthma or arthritis. 
Last but not least, a 2004 study concluded that Hemlock Varnish Shelf also possessed liver protective properties as well as being anti-fibrotic. 
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.