The patient is a 48-year-old man with a history of a rectal adenocarcinoma (cT3N2bM0) diagnosed 9 years prior. Following neoadjuvant chemoradiotherapy, low anterior resection, and 6 cycles of adjuvant FOLFOX therapy (fluorouracil, leucovorin, and oxaliplatin), he had developed a lung metastasis (KRAS wild type) 1 year later. He subsequently developed multiple lung metastases treated with palliative local interventions (lobectomy, radiofrequency ablation) and 4 lines of chemotherapy. Owing to symptomatic lung disease, he was enrolled in a clinical trial (NCT03502733) following informed consent and achieved a confirmed partial response. After 9 months, contrast computed tomography restaging scans noted a new, 1-cm posterior subglottic lesion of unclear origin (Figure , A). He had no shortness of breath or noisy breathing, dysphagia, voice change, or hemoptysis. A partial response was maintained without evidence of progression of lung disease.Otolaryngology was consulted to assess the lesion. The differential diagnosis based on imaging included a mass vs inspissated mucus. Examination using distal-chip flexible laryngoscopy revealed a 1-cm, broad-based, exophytic mass along the posterior wall of the subglottis with prominent vasculature. No other anatomic abnormalities in the upper aerodigestive tract or cervical lymphadenopathy were noted. The decision was made to proceed to the operating room for definitive endoscopic biopsy under general anesthesia (Figure , B). Examination revealed a subglottic mass that did not extend inferiorly beyond the caudal aspect of the cricoid cartilage. The mass was debulked and sent to pathology for analysis, including hematoxylin-eosin and immunohistochemical staining (Figure , C).