Xitronix Corporation v. Kla-Tencor Corporation, 882 F.3d 1075

Xitronix sued in the U.S. District Court for the Western District of Texas under Walker Process (Sherman Act §2 and Clayton Act §§4,6), alleging KLA fraudulently procured U.S. Patent No. ’260 and used it to monopolize the market.
The district-court action asserted fraud on the PTO as the predicate for an antitrust monopolization claim; the complaint focuses on misrepresentations made during patent prosecution.
Xitronix (the plaintiff) and KLA both initially treated the appeal as within the Federal Circuit’s exclusive appellate jurisdiction under 28 U.S.C. §1295(a)(1).
After the court sua sponte raised jurisdictional questions, the parties briefed whether the Federal Circuit has jurisdiction, but did not initially address the Supreme Court’s decision in Gunn v. Minton.
The Federal Circuit analyzed whether the Walker Process claim “arises under” patent law under the well-pleaded-complaint rule and Gunn, concluding that although patent issues may be involved as a “case within a case,” the claim does not necessarily depend on a substantial federal patent question.
The Federal Circuit held it lacked appellate jurisdiction and transferred the appeal to the U.S. Court of Appeals for the Fifth Circuit.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the Federal Circuit has exclusive appellate jurisdiction under 28 U.S.C. §1295(a)(1) over a Walker Process monopolization claim based on alleged fraud in PTO prosecution	The claim depends on patent law and thus falls within the Federal Circuit’s exclusive jurisdiction (pointing to Nobelpharma and Cipro)	The claim is a fact-bound antitrust claim alleging fraud/misrepresentation; patent law is only a component and not a substantial federal question for exclusive jurisdiction	The court held the Federal Circuit lacks jurisdiction: patent law is a "case within a case" but not a substantial federal issue under Gunn; transferred the appeal to the Fifth Circuit

Christianson v. Colt Indus. Operating Corp., 486 U.S. 800 (well-pleaded-complaint rule limits "arising under" patent jurisdiction)
Holmes Grp., Inc. v. Vornado Air Circulation Sys., Inc., 535 U.S. 826 (interpretation of "arising under" and well-pleaded-complaint focus on claims)
Gunn v. Minton, 568 U.S. 251 (patent-related "case within a case" does not confer federal jurisdiction unless the patent issue is substantial to the federal system)
Nobelpharma AB v. Implant Innovations, Inc., 141 F.3d 1059 (Fed. Cir.) (applied Federal Circuit law to Walker Process claims but did not hold all such claims fall within exclusive appellate jurisdiction)
In re Ciprofloxacin Hydrochloride Antitrust Litig., 544 F.3d 1323 (Fed. Cir.) (treated Walker Process issues under Federal Circuit law when jurisdiction was not disputed)
Walker Process Equip. v. Food Mach. & Chem. Corp., 382 U.S. 172 (Walker Process doctrine: enforcing a patent procured by fraud can be an antitrust violation)
Owen Equip. & Erection Co. v. Kroger, 437 U.S. 365 (courts must respect limits on federal jurisdiction)