From the article:
"Remarks: The fruiting bodies of P. pini vary considerably in morphology, on different hosts. Phellinus pini might be confused with early incipient decay caused by Echinodontium tinctorium, or the natural reddish discoloration in some pines Other fungi also produce a white pocket rot; Phellinus nigrolimitatus and Hericium abietis produce larger pockets with well-defined margins, Inonotus tomentosus and Dichomitus squalens (P. Karst) D. Reid form pockets with poorly defined margins."