From pulmonary embolism to small intestinal neuroendocrine tumor: A new diagnostic perspective.

Pulmonary embolism is a common and potentially life-threatening acute condition encountered in clinical practice. Neuroendocrine tumors are heterogeneous neoplasms characterized by diverse biological behaviors, and patients with poorly differentiated or advanced neuroendocrine tumors may have an increased risk of developing venous thromboembolism. We report the case of a 60-year-old female who experienced acute chest discomfort and was diagnosed with pulmonary embolism. Comprehensive evaluation revealed no evidence of lower limb thrombosis, autoimmune or hematologic disorders, or other identifiable causes. The emboli resolved following anticoagulant therapy. Seventeen months later, the patient developed upper abdominal pain and underwent a colonoscopy, which revealed a lesion approximately 20 cm proximal to the terminal ileum. Histopathological and immunohistochemical analyses confirmed a grade-1 neuroendocrine tumor. 18F-octreotide positron emission tomography-computed tomography demonstrated increased tracer uptake in the terminal ileum and multiple hepatic foci, consistent with an ileal neuroendocrine tumor with liver metastases. The patient received intramuscular octreotide acetate microspheres (20 mg every 4 weeks) and remained clinically stable during follow-up. This case underscores the importance of considering occult malignancy in older patients presenting with unprovoked pulmonary embolism. Small intestinal neuroendocrine tumors may remain clinically silent for extended periods and should be included in the differential diagnosis when common etiologies have been excluded.