A80-3-09 Lung Adenocarcinoma Disguised as Bilateral Lower Extremity Weakness in a Young Woman

Abstract Introduction Lung cancer ranks as the second most prevalent cancer in the United States; however, it is relatively rare in younger adults, with only 10% of cases diagnosed in individuals younger than 55. Both young and older patients may present with pulmonary symptoms; however, atypical symptoms are more common in younger individuals largely due to delayed diagnosis. We add to the literature a case of lung adenocarcinoma in a young adult who presented with bilateral lower extremity weakness. Case A 40-year-old woman presented to the emergency department with two months of progressively worsening bilateral lower extremity weakness and urinary incontinence. Her medical history included a ten-year smoking history, with tobacco cessation 15 years ago. In the outpatient setting, she was started on steroids for a positive antinuclear antibody and anti-smith antigen/ribonucleoprotein antibody by rheumatology. She was also seen by neurology who recommended hospital admission for evaluation of Guillain- Barré Syndrome. An x-ray of the chest was obtained due to leukocytosis in the setting of steroid use, which was significant for a 10.5 x 10.5 cm right upper lung mass. CT chest confirmed a large irregular mass with mass effect on the adjacent right mainstem bronchus with severe narrowing. She denied any respiratory symptoms. MRI spine revealed an intramedullary spinal lesion at the conus medullaris with vasogenic cord edema and MRI brain showed three right cerebral lesions, concerning for metastatic lung cancer. Biopsy of the lung mass revealed poorly differentiated adenocarcinoma with 90% programmed death- ligand 1 positivity. The patient received radiation of metastatic lesions and was discharged with steroids and follow-up with oncology to begin palliative immunotherapy. She continued to decompensate and ultimately passed away approximately two months after initial cancer diagnosis. Discussion This unfortunate case underscores the challenges in diagnosing lung cancer in younger adults. Younger patients are more likely to have stage IV disease and atypical symptoms at diagnosis, potentially due to initial misdiagnosis. Lung cancer is often excluded from the differential diagnosis in young patients, as it has historically been more common in older patients. Once diagnosed, younger patients are more likely to have targetable mutations, which confers greater survival benefit when compared to older adults. Through this case, we argue that lung malignancy be considered in the differential for young patients with pulmonary and extra-pulmonary symptoms in order to identify early-stage disease. This abstract is funded by: None