Summary:
Features include 1) flat growth on wood (or may be bent back to form shelving caps that are cinnamon brown and tomentose in narrow often slightly grooved zones), 2) a pore surface that is a shade of brown with round to maze-like pores, 3) flesh that is often duplex: white becoming cinnamon toward substrate or cap, or with a thin black line next to substrate or cap base, 4) relatively large cylindric spores, and 5) other microscopic characters. The online Species Fungorum, accessed November 16, 2020, listed the current name as Neoantrodia variiformis, but MycoBank, accessed the same day, listed the current name as Antrodia variiformis. The description is derived from Gilbertson(1).

Microscopic:
spores 8-12 x 3-4.5 microns, cylindric, "often slightly arcuate close to the apiculus", inamyloid, colorless; basidia 25-35 x 6-8 microns, clavate; cystidia none, but colorless "slightly ventricose cystidioles may occur scattered among the basidia, 28-42 x 4-6.5 microns"; hyphal system dimitic or trimitic, generative hyphae with clamp connections, in context 2-5 microns and mostly slightly thick-walled, in trama and subhymenium 2-4 microns, thin-walled, and frequently branched, skeletal hyphae 2-6 microns, thick-walled to solid, straight, occasionally dichotomously branched, there may also be a third type of hyphae at the base of the context more frequently branched and more narrow, "which may be interpreted as binding hyphae or as the ends of more arboriform skeletal hyphae"

Notes:
Antrodia variiformis has been found in BC, WA, OR, ID, AB, ON, PQ, NB, NF, NS, YT, AK, CO, ME, MI, MN, MT, NH, NY, TN, UT, VT, and WY, and is found circumglobally in boreal forests (Europe, Asia), as well as being introduced in pine plantations in East Africa, (Gilbertson).

Synonyms and Alternate Names:
Clavaria truncata Quel.
Polyporus variiformis Peck