
    Andrew J. MAYO, Plaintiff-Appellant, v. FEDERAL GOVERNMENT, Dr. Ira Jasser, Bronx VA, Bronx VA Hospital, Johnson and Johnson, Man VA Hospital, Mann VA, Defendants-Appellees.
    No. 12-4192.
    United States Court of Appeals, Second Circuit.
    March 11, 2014.
    Andrew J. Mayo, pro se, White Plains, NY, for Plaintiff-Appellant.
    Carina Hyatt Schoenberger, Assistant United States Attorney (Sarah Sheive Normand, Ellen London, and Benjamin H. Torrance, Assistant United States Attorneys, on the brief), for Preet Bharara, United States Attorney for the Southern District of New York, New York, NY, for Defendants-Appellees Federal Government, Dr. Ira Jasser, Bronx VA, Man VA Hospital, Mann VA.
    Jenya Moshkovich (John D. Winter, on the brief), Patterson Belknap Webb & Tyler LLP, New York, NY, for Defendant-Appellee, Johnson and Johnson.
    PRESENT: ROBERTA. KATZMANN, Chief Judge, ROBERT D. SACK, Circuit Judge, and EDGARDO RAMOS, District Judge.
    
      
       The Honorable Edgardo Ramos, of the United States District Court for the Southern District of New York, sitting by designation.
    
   SUMMARY ORDER

Appellant Andrew Mayo, proceeding pro se, appeals from a judgment entered by the United States District Court for the Southern District of New York (Ellis, M.J.) dismissing his claims for medical malpractice, products liability, and violation of his constitutional right to privacy. We assume the parties’ familiarity with the underlying facts, the procedural history of the case, and the issues on appeal.

A court normally may not look beyond the four corners of the complaint in considering a motion to dismiss. See Friedl v. City of New York, 210 F.3d 79, 83 (2d Cir.2000). However, a court may convert a motion to dismiss into a motion for summary judgment by considering extrinsic evidence, as long as the opposing party receives sufficient notice and an opportunity to respond. See Hernandez v. Coffey, 582 F.3d 303, 307-08 (2d Cir.2009). Here, although the court considered evidence outside of the complaint, the defendants provided Mayo with unequivocal notice of the court’s ability to treat their motions as motions for summary judgment. See id. Mayo was also afforded the opportunity to submit further evidence, and took advantage of that opportunity. We therefore find that the magistrate judge properly converted the motions before it into motions for summary judgment.

We review orders granting summary judgment de novo and focus on whether the district court properly concluded that there was no genuine issue as to any material fact and the moving party was entitled to judgment as a matter of law. See Miller v. Wolpoff & Abramson, L.L.P., 321 F.3d 292, 300 (2d Cir.2003). We are required to resolve all factual ambiguities and draw all reasonable inferences in favor of the nonmovant. See Nationwide Life Ins. Co. v. Bankers Leasing Ass’n, 182 F.3d 157, 160 (2d Cir.1999) (citing Cronin v. Aetna Life Ins. Co., 46 F.3d 196, 202 (2d Cir.1995)). Summary judgment is appropriate “[wjhere the record taken as a whole could not lead a rational trier of fact to find for the non-moving party.” Matsushita Elec. Indus. Co. v. Zenith Radio Corp., 475 U.S. 574, 587, 106 S.Ct. 1348, 89 L.Ed.2d 538 (1986). We review de novo a district court’s determination that a claim is barred by the statute of limitations, A.Q.C. ex rel. Castillo v. United States, 656 F.3d 135, 140 (2d Cir.2011), and review its decision not to apply equitable tolling for abuse of discretion, id. at 144.

Mayo has not raised any substantive challenge to the district court’s legal analysis in his briefing. He has therefore forfeited any such challenge. See LoSacco v. City of Middletown, 71 F.3d 88, 92-93 (2d Cir.1995). In any event, his claims must fail for the reasons articulated in the district court’s opinions below.

After an independent review of the record, we conclude that the district court properly found Mayo’s claims barred by the respective statutes of limitation. See 28 U.S.C. § 2401(b); N.Y. C.P.L.R. §§ 214(5), 214-c(2). We also perceive no abuse of discretion in the district court’s decision that Mayo was not entitled to equitable tolling. “Generally, a litigant seeking equitable tolling bears the burden of establishing two elements: (1) that he has been pursuing his rights diligently, and (2) that some extraordinary circumstance stood in his way.” Castillo, 656 F.3d at 144 (quoting Pace v. DiGuglielmo, 544 U.S. 408, 418, 125 S.Ct. 1807, 161 L.Ed.2d 669 (2005)). As Mayo did not show that either of these two elements was met, the district court properly refused to apply equitable tolling.

Finally, the court properly dismissed Mayo’s Bivens claim because Mayo offered no evidence from which a reasonable jury could conclude that he was subjected to medical experimentation.

We have considered Mayo’s remaining arguments and find them to be without merit. Accordingly, we AFFIRM the judgment of the district court. 
      
      . We therefore need not resolve whether the FTCA’s statute of limitations ever permits equitable tolling. See Phillips v. Generations Family Health Ctr., 723 F.3d 144, 149, 155 n. 8 (2d Cir.2013).
     