Abstract Introduction Elevated pleural fluid amylase typically suggests pancreatitis, pleuro-pancreatic fistula, or esophageal perforation. Malignant pleural effusions (MPE) can also demonstrate amylase elevation - a less recognized association that may misdirect clinicians toward extensive abdominal investigation and delay cancer diagnosis. Lung adenocarcinoma, in particular, has been reported to produce salivary-type amylase isoenzymes, resulting in significantly increased pleural amylase levels. Early recognition of this rare but important phenomenon can reduce delays in diagnostics for oncologic care. Case Presentation A 47-year-old man with a history of tobacco use disorder, gastroesophegeal reflux disease, and hyperlipidemia presented with several weeks of progressive dyspnea. Chest CT revealed a large left pleural effusion with mediastinal shift and compressive atelectasis. (Fig 1). A pigtail catheter was placed, and pleural studies demonstrated an exudative effusion by Light’s criteria, with markedly elevated amylase at 2,623 U/L (serum amylase 179 U/L). Repeat testing confirmed elevated pleural amylase. The patient denied abdominal pain, dysphagia, or alcohol use. Given the high pleural amylase level, evaluation for pancreatitis, pleuro-pancreatic fistula, and occult esophageal perforation was performed. CT abdomen/pelvis demonstrated no pancreatic or esophageal pathology. Following drainage, interval chest CT revealed near-complete resolution of the effusion, and the patient’s symptoms improved. The pleural catheter was removed, and the patient was discharged with cytology pending. Pleural cytology subsequently resulted positive for adenocarcinoma, confirming malignant pleural effusion. The patient was notified and promptly referred to medical oncology for further staging and initiation of treatment. Clinical Implications This case demonstrates that markedly elevated pleural amylase, although classically attributed to pancreatic or esophageal pathology, can also accompany malignant pleural effusions. When abdominal imaging is unrevealing or symptoms are discordant, clinicians should broaden the differential, as tumor-related ectopic or salivary-type amylase production has been described. Recognizing this association may help avoid unnecessary abdominal evaluation, shorten time to diagnosis, and facilitate earlier oncologic referral. Additionally, large pleural effusions may obscure underlying masses; therefore, repeat chest imaging or tissue sampling should be considered when amylase remains markedly elevated. Recognizing the “pancreatic red herring” can redirect diagnostic focus and improve outcomes in patients with malignant pleural effusions. This abstract is funded by: None
Zafar et al. (Fri,) studied this question.