Summary:
Features include 1) resupinate growth on fir, 2) a waxy fruitbody colored yellowish but becoming ochraceous or pale brown, the surface smooth but cracking when old, 3) smooth, inamyloid, and colorless spores that are oblong to nearly round with a sublateral apiculus and oily substance dispersed in the protoplasm, 4) clavate 4-spored basidia, 5) filiform hyphidia, 6) cystidia that are usually enclosed, and 7) a monomitic hyphae system, the individual hyphae with clamp connections and indistinct. The online Species Fungorum, accessed October 6, 2018, gave the current name as Cerocorticium sulfureoisabellinum in Meruliaceae instead of in the genus Flavophlebia (in Pterulaceae) , but MycoBank, accessed the same day, gave the current name as Flavophlebia sulfureoisabellina.

Microscopic:
SPORES 7-8 x 5-6 microns, oblong, nearly round or rarely round, with distinct sublateral apiculus, smooth, inamyloid, acyanophilic, thin-walled, with oily substance dispersed in the protoplasm; BASIDIA 4-spored, terminal, 20-30 x 6-8 microns, clavate, with basal clamp connection; CYSTIDIA 50-80 x 6 microns, enclosed or slightly projecting, cylindric or subfusiform, thin-walled; HYPHAE monomitic, individual hyphae mostly indistinct, 2-2.5 microns wide, thin-walled, those of the subhymenium sparsely branched, all hyphae with clamp connections, (Hjortstam), SPORES 5-8 x 5-6 microns, HYPHIDIA found in genus are filiform, some weakly branched, (Ginns(23)), SPORES 5.5-7 x 5-6 microns, round or nearly round, slightly compressed laterally with distinct apiculus, smooth, inamyloid, colorless, thin-walled, multiguttulate or uniguttulate; BASIDIA 4-spored, 20-40 x 7-8.5 microns, "broadly clavate, tapering from slender hyphal base", sterigmata 8-10 microns long, subulate, somewhat arcuate or nearly straight; PARAPHYSES in hymenium "hyphal-like, flexuous, branching, tortuous to subclavate"; GLOEOCYSTIDIA 35-75 x 5.5-8 microns, cylindric to subclavate, flexuous [wavy]; "subiculum somewhat indistinct, basal hyphae horizontal, conglutinate, vertical hyphae densely entangled, with clamps at septa, wall thin becoming collapsed and indistinct", (Jackson)

Notes:
It has been found in BC, NS, ON, PQ, MN, and NH, (Ginns), Austria, France, Poland, and not uncommon in Carpathian Mountains, (Hjortstam), and Czechoslovakia (Jackson).