Nuclear Protein in Testis (NUT) Carcinoma: Diagnostic Challenges in a Patient Requiring Rescue Venovenous...

Nuclear protein in testis (NUT) carcinoma is a rare, highly aggressive malignancy defined by NUTM1 rearrangement, most commonly involving BRD4. Nonspecific presentation and poorly differentiated histology lead to frequent misdiagnosis. Patients often present with large mediastinal masses, making swift diagnosis both important and challenging. A 29-year-old woman presented with two months of progressive dyspnea, cough, and fatigue accompanied by new-onset hemoptysis. CT demonstrated a large right hilar and mediastinal mass compressing the trachea, pulmonary artery, and superior vena cava (SVC). Rigid bronchoscopy was planned for biopsy and possible therapeutic debulking to control hemoptysis; the extracorporeal membrane oxygenation (ECMO) team was on standby, but the patient was not pre-cannulated. During induction of anesthesia, she developed profound refractory hypoxemia that persisted despite jet ventilation and airway optimization, attributed to loss of spontaneous respiratory effort and muscle tone with worsening dynamic central airway compression. Emergent femoral-femoral venovenous extracorporeal membrane oxygenation (VV-ECMO) was initiated, allowing the procedure to proceed safely. Bronchoscopy demonstrated severe right mainstem bronchial stenosis and complete obstruction of the right upper lobe by a friable endobronchial mass. Biopsies were nondiagnostic because of extensive necrosis and crush artifact, but the findings defined the extent of endobronchial disease and guided subsequent diagnostic planning. She was decannulated after two days of support, following clinical improvement sufficient to tolerate sitting upright. Supraclavicular lymph node sampling then established NUT carcinoma, confirmed by NUT immunohistochemistry (clone C52B1). Chemotherapy could not be initiated because of her critical clinical state, and she died two weeks after diagnosis. NUT carcinoma presents with nonspecific respiratory symptoms and is usually diagnosed at an advanced stage. Extensive necrosis reduces endobronchial biopsy yield, and alternative tissue sites should be pursued when initial sampling is nondiagnostic. Large mediastinal masses confer high risk of airway collapse and cardiovascular compromise during sedation; this case suggests that pre-emptive cannulation, rather than standby availability, warrants consideration when tracheal, pulmonary artery, and SVC compression coexist. VV-ECMO can stabilize patients with life-threatening respiratory failure and bridge them to definitive diagnostic evaluation. NUT carcinoma should be considered in young patients with rapidly progressive thoracic masses and poorly differentiated malignancy, with early confirmatory immunohistochemical or molecular testing.