An Early-Stage Nuclear Protein in Testis Carcinoma of the Lung in an Older Woman.

A nuclear protein in testis (NUT) carcinoma is a rare, aggressive malignancy often diagnosed late due to non-specific symptoms and low awareness. A 69-year-old woman presented with haemoptysis and a positron emission tomography-avid lung nodule (cT1N0M0). An initial bronchoscopic biopsy suggested small cell carcinoma with negative NUT staining. Following a lobectomy, immunohistochemical analysis showed strong nuclear NUT positivity, and fluorescence in situ hybridization confirmed NUT rearrangement. This case was atypical due to the patient's age, early stage, and initial misdiagnosis from a limited biopsy. The non-specific presentation of an NUT carcinoma requires a high degree of suspicion, and small biopsies risk a misdiagnosis.