Introduction: This vignette highlights the development of localized rectal adenocarcinoma and concomitant metastatic large cell neuroendocrine tumor of the lung in a patient with longstanding Crohn’s disease (CD) on Vedolizumab (VDZ). Case Description/Methods: A 61 year old male with a 2 year history of severe, uncontrolled colonic inflammatory CD presented to the ED with weakness, loss of appetite, and a 30lb weight loss over a 1 month period. He had been on VDZ 300mg every 8 weeks for 1 year. A CT chest showed a new 2cm pulmonary nodule with increasing mediastinal and perihilar lymphadenopathy. Bronchoscopy and endobronchial ultrasound were performed for lymph node sampling and revealed a large cell neuroendocrine tumor, which was later found to be metastatic to the brain. The patient was discharged with plans to optimize the VDZ therapy and start cancer treatment. Anticipating the use of immunotherapy, a colonoscopy was performed and revealed active inflammation in the sigmoid colon. Incidentally, an 18mm Is (sessile) polyp was found in the rectum and removed by piecemeal snare polypectomy. Pathology was consistent with invasive colonic adenocarcinoma. A colonoscopy one year earlier had been negative for malignancy. After a careful discussion in the GI tumor board, the decision was made to treat the lung cancer first. Unfortunately, the patient developed sepsis after his first chemotherapy dose and passed away. Discussion: This case illustrates the challenges with CD therapy during active malignancy. CD patients are at increased risk for both colonic adenocarcinoma and pulmonary malignancy. There have been isolated cases linking CD to premalignant diffuse idiopathic pulmonary neuroendocrine cell hyperplasia, suggesting a possible correlation between CD and the highly aggressive large cell neuroendocrine tumor of the lung seen, though data is limited. VDZ has been associated with 24%-31% clinical remission of CD after induction. It was shown to be well tolerated and had a low risk of malignancy in patients with and without a history of prior malignancy. Data is limited on the use of VDZ concurrently with active chemotherapy, though it is presumed have a favorable safety profile given the gut-selective nature of the drug. The development of malignancies in this case is thought to be possibly related to CD and likely unrelated to VDZ. With limited data available, a multidisciplinary discussion between oncology and GI is ideal to develop a tailored treatment plan for CD patients with active malignancy.