By Scott Jarratt (February 26, 2018, 1:14 PM EST) -- In MaxLinear Inc. v. CF Crespe LLC., No. 2017-1039, 2018 U.S. App. LEXIS 1930 (Fed. Cir. Jan. 25, 2018), the Federal Circuit vacated and remanded the Patent Trial and Appeal Board's final written decision in IPR2015-00592 (the '592 IPR). The PTAB had found that all instituted claims were not shown to be unpatentable, but during the pendency of the appeal, the Federal Circuit affirmed a decision in another inter partes review finding the same patent's independent claims unpatentable. The Federal Circuit then held that collateral estoppel applied and vacated the board's decision. Because the PTAB focused solely on the now-invalid independent claims in its decision, the court ordered the PTAB to consider on remand whether the dependent claims were "patentably distinct." However, the Federal Circuit's guidance on this point presents logical and procedural uncertainties for the PTAB, as it has been directed to consider prior art not of record in the underlying IPR....