C80-10 Beyond the Lung Parenchyma: Striking Radiologic Presentation of Small Cell Lung Cancer With Left Pulmonary Artery Involvement

Abstract Small-cell lung cancer (SCLC) is a high-grade neuroendocrine malignancy accounting for approximately 10-15% of all lung cancers. It presents as a rapidly growing tumor located centrally in the lung and is strongly associated with tobacco use (Devault, Kyle et al). Although SCLC is known for its aggressive and rapid progression, it is relatively rare for the tumor burden to be so extensive that it nearly occludes a major pulmonary artery and adjacent bronchus. We present a unique case of SCLC with near engulfment of the left pulmonary artery with significant mass effect and compensatory dilation of the right pulmonary artery. A 65-year-old male with a 54 pack-year smoking history, hypertension, and obstructive sleep apnea was brought to the emergency department by his wife due altered mental status and a home oxygen saturation reading of SpO2 80% on room air. Earlier that week he had been seen by cardiothoracic surgery (CT surgery) for evaluation of a chest CT scan showing a pulmonary mass; a bronchoscopy had been performed, and results were pending. He presented now with worsening shortness of breath and hemoptysis; arterial blood gas demonstrated mild respiratory acidosis. He was initiated on supplemental oxygen and BIPAP, with subsequent improvement in his respiratory acidosis.Given his tachycardia and hypoxemia, a contrast-enhanced CT pulmonary angiogram was obtained to evaluate for pulmonary embolism (PE). No PE was identified; instead, the scan revealed a large 12 × 9.8 × 12 cm lesion in the left upper lobe (Figure 1), demonstrating circumferential compression of the left pulmonary artery, obstruction of the left distal bronchi, and concomitant dilation of the right pulmonary artery. Pulmonology and CT surgery were consulted; surgical stenting/debulking was deemed not feasible. He was treated with broad-spectrum antibiotics for presumed post-obstructive pneumonia and oncology was consulted. His biopsy returned positive for SCLC, and inpatient chemotherapy was initiated promptly. His hypoxia resolved, and he was discharged on room air with close follow-up arranged with pulmonology, oncology, and CT surgery for ongoing oncologic management. Small-cell lung cancer is an exceptionally aggressive malignancy with rapid doubling time, early metastasis, and poor long-term prognosis. This case is notable for its extraordinary imaging presentation: while central masses are common in SCLC, complete involvement of the entire left pulmonary artery with mass effect and contralateral vascular dilation is exceedingly unusual. The imaging alone warrants recognition, and the case underscores the spectrum of vascular invasion. This abstract is funded by: none