Nonmetastatic Pulmonary Carcinoid Presenting With Carcinoid Syndrome Despite Negative 5‐HIAA: A Case Report

Background: Carcinoid syndrome from pulmonary carcinoids without hepatic metastases is rare and diagnostically challenging when biochemical markers are normal. Case Presentation: A woman in her mid-60 s presented with an incidental right adrenal mass during evaluation for dyspnea and elevated D-dimer. She reported a 20-year history of paroxysmal tachycardia and 5 years of episodic flushing, profuse sweating, exertional dyspnea, and fine tremors triggered by minimal physical activity. Imaging revealed a 3.6 cm lipid-rich adrenal adenoma and an 8 × 10 mm left upper lobe pulmonary nodule. Comprehensive biochemical evaluation was normal: 24 h urinary 5-hydroxyindoleacetic acid 6 mg/d (normal 0-15), chromogranin A 50 ng/mL (normal 0-187), plasma metanephrine 0.12 nmol/L (normal 0.00-0.49), and normetanephrine 0.68 nmol/L (normal 0.00-0.89), excluding pheochromocytoma. Fine needle aspiration of the left pulmonary nodule confirmed a typical carcinoid tumor. Left upper lobe trisegmentectomy revealed low-grade neuroendocrine neoplasm (pT1b pN0) with minimal mitotic activity (