B80-5-08 An Unusual Presentation of FGFR3-TACC3 Positive Lung Adenocarcinoma Presenting With a Miliary Pattern and Vision Loss

Introduction Although rare, primary lung adenocarcinoma can present with a miliary pattern, which is most often associated with EGFR or ALK mutations. This case highlights an unusual presentation of primary lung adenocarcinoma with vision loss as the first presenting symptom and a miliary pattern on computed tomography (CT) associated with a FGFR3-TACC3 fusion mutation. Case A 72-year-old male with past medical history of 12.5 pack-year smoking history who quit 30 years prior, hypertension, ischemic cardiomyopathy, and hyperlipidemia presented to his PCP due to several weeks of feeling ill which initially started with nausea, vomiting, and diarrhea. A CT of the abdomen and pelvis was ordered due to concern for diverticulitis. The CT did show mild diverticulitis and incidentally noted diffuse parenchymal miliary nodules of the bilateral lungs. The patient did not seek further medical care until a month later after he developed flashes and shading in his central right vision. At this point, he was found to have a choroidal lesion concerning for potential metastatic lung cancer. Oncologic workup with circulating tumor DNA and subsequent tissue biopsy from the left lung showed a FGFR3-TACC3 fusion driver mutation. Positron emission tomography/computed tomography (PET/CT) showed evidence of metastatic disease to the brain, spine, liver, and colon. The patient was planned for palliative chemotherapy following his lung biopsy, but unfortunately, he developed a pneumothorax while undergoing bronchoscopy for tissue biopsy requiring chest tube placement. He continued to deteriorate clinically and was discharged home on hospice just two months after his initial diagnosis. Discussion This case represents a rare occurrence of a miliary pattern of primary biopsy-confirmed lung adenocarcinoma, with the first symptomatic presentation being vision changes from choroidal metastasis. FGFR3-TACC3 fusions are an uncommon cause of lung adenocarcinoma and have been found to account for around 0.6% of cases, especially in the setting of a miliary pattern since most examples of miliary lung adenocarcinoma are associated with EGFR mutations. This case highlights the need to consider adenocarcinoma on the differential for miliary lung nodules and to pursue a broad work-up including molecular screening and biopsy, after more common causes of miliary lesions are ruled out, to ensure quick and accurate treatment initiation. This abstract is funded by: None