We granted certiorari to review the Court of Appeals’ opinion in Holmes v. Nat’l Servs. Indus., Op. No.2009-UP-364 (S.C. Ct.App. filed June 25, 2009).1 We affirm.
FACTS
Petitioner began working for respondent National Service Industries (“National”), a linen company, at its Charleston laundering facility in August 1984. According to petitioner, the work environment at the facility was “very hot” and “sticky” with “a lot of lint and dust in the air,” and was poorly ventilated. Petitioner was exposed to the fumes of bleach and did not wear a protective mask.
In 1992, petitioner began experiencing breathing and sinus problems. Petitioner never experienced breathing or sinus problems prior to working for National. Petitioner’s breathing was “good” when she was away from work. In 1993, National transferred petitioner to its Atlanta facility where the working conditions were worse than in the Charleston facility. Petitioner ultimately left her employment with National because the working conditions were making her breathing problems worse.
In 1995, petitioner visited Dr. Jefrey Lieberman, who diagnosed petitioner as suffering from sarcoidosis, a respiratory and pulmonary condition. Petitioner testified Dr. Lieberman told her he did not know what caused her sarcoidosis and that, *308in light of this statement, she took no further steps to determine the cause of her condition.
In July 2005, petitioner visited Dr. Michael Spandorfer. Dr. Spandorfer stated in his report that it was unclear whether petitioner’s work exposure at National caused her sarcoidosis, but that it was more likely that petitioner’s exposure to the airborne particles and fumes worsened her condition, which had previously developed.
Petitioner filed a workers’ compensation claim alleging a compensable injury by accident to her lungs and respiratory system arising out of and in the scope of her employment with National on July 12, 2005, the date she alleges she first discovered her sarcoidosis was related to her employment.
The single commissioner found petitioner sustained a compensable injury by accident to her lungs which was discovered on July 12, 2005.
The full commission reversed the commissioner, finding petitioner’s claim was barred by the two-year statute of limitations. Specifically, the full commission found petitioner was aware of her working conditions and, with some diligence on her part, could have discovered she had a claim more than two years before her filing date.
Petitioner appealed. The circuit court and Court of Appeals, pursuant to Rule 220(b), SCACR, affirmed the full commission’s determination that petitioner failed to file her claim within the statute of limitations.
STANDARD OF REVIEW
In workers’ compensation cases, the Commission is the ultimate fact finder. Jordan v. Kelly Co., 381 S.C. 483, 674 S.E.2d 166 (2009). An appellate court must affirm the findings made by the Commission if they are supported by substantial evidence. Pierre v. Seaside Farms, Inc., 386 S.C. 534, 540, 689 S.E.2d 615, 618 (2010). “Substantial evidence is not a mere scintilla of evidence, but evidence which, considering the record as a whole, would allow reasonable minds to reach the conclusion the agency reached.” Id. The substantial evidence test “need not and must not be either judicial fact-finding or a substitution of judicial judgment for agency *309judgment;” and a judgment upon which reasonable men might differ will not be set aside. Lark v. Bi-Lo, Inc., 276 S.C. 130, 136, 276 S.E.2d 304, 307 (1981) (quoting Dickinson-Tidewater, Inc. v. Supervisor of Assess., 273 Md. 245, 329 A.2d 18, 25 (Md.1974)).
LAW/ANALYSIS
Petitioner argues the Court of Appeals erred in holding substantial evidence in the record supported the full commission’s finding that petitioner’s claim was barred by the statute of limitations. We disagree.
The right to workers’ compensation for an injury by accident “is barred unless a claim is filed with the commission within two years after an accident....” S.C.Code Ann. § 42-15-40 (Supp.2010).
Under the discovery rule, the statute of limitations begins to run from the date the claimant knew or should have known that, by the exercise of reasonable diligence, a cause of action exists. Mauldin v. Dyna-Color/Jack Rabbit, 308 S.C. 18, 20, 416 S.E.2d 639, 640 (1992).
Whether petitioner knew or should have known that her sarcoidosis was related to her employment with National over two years before filing her claim in 2005 is a question of fact for the commission. In our view, the Court of Appeals correctly held that substantial evidence in the record supported the full commission’s finding that petitioner’s claim was barred by the statute of limitations. Considering the record as a whole, there is substantial evidence that would allow reasonable minds to reach the conclusion that petitioner should have known she had a compensable injury when first diagnosed with sarcoidosis. Pierre, supra. There is evidence petitioner knew or should have known as early as 1992 her work environment was negatively affecting her health. Petitioner testified she experienced breathing problems and lesions when she was working at National’s Charleston facility. Petitioner also testified her breathing was “good” when she was away from work and that she ultimately left her employment with National because the working conditions were making her breathing problems worse. Although reasonable *310minds may differ as to whether petitioner should have known after being diagnosed with sarcoidosis that she had a compensable injury, this is not sufficient to set aside the judgment of the Appellate Panel. Lark, supra.
We requested the parties address whether the commission’s findings regarding compensability and causation are the law of the case. Because we affirm the Court of Appeals’ opinion regarding the statute of limitations issue, we decline to address this issue. See Futch v. McAllister Towing of Georgetown, Inc., 335 S.C. 598, 518 S.E.2d 591 (1999) (when one issue is dispositive, the remaining issues need not be addressed).
CONCLUSION
The Court of Appeals correctly found there was substantial evidence in the record to support the full commission’s findings that petitioner’s claim was barred by the statute of limitations. Accordingly, the opinion of the Court of Appeals is
AFFIRMED.
KITTREDGE, J., and Acting Justice E.C. BURNETT, III, concur. BEATTY, J., dissenting in a separate opinion in which Acting Justice JAMES E. MOORE, concurs.. This Court has corrected the spelling of the employer's name to "National Service Industries” (rather than "National Services Industries”) in the caption.