Persistent AST Elevation in a Patient With Ovarian Cancer: A Rare Diagnostic Challenge

Background: Persistent elevation of aspartate aminotransferase (AST) is commonly indicative of liver injury or disease, but isolated AST elevation without concurrent alanine aminotransferase (ALT) increase is rare and difficult to diagnose. While AST is non-specific and found in various tissues, its isolated elevation is due to less common conditions, such as macro-AST, where AST binds with immunoglobulins creating a high-molecular-weight complex that affects serum activity. Case Description: A 68-year-old female with a history of high-grade serous ovarian cancer (HGSOC) who had persistent isolated AST elevation for several years. Evaluations including physical exams, imaging, and routine liver function tests showed no evidence of hepatic or muscular disease. The polyethylene glycol (PEG) precipitation significantly reduced serum AST activity, confirming the presence of the macro-enzyme form of AST (macro-AST). Conclusion: This case highlights the rare and novel occurrence of macro-AST in a patient with ovarian cancer. It emphasizes the importance of considering macro-AST in the differential diagnosis of isolated AST elevation, particularly in patients without clear evidence of liver or muscular disease. Recognizing this benign condition can prevent unnecessary diagnostic procedures and anxiety.