Metastatic pulmonary pleomorphic carcinoma involving the jejunum: a case report and review of the literature.

We present a case report of a pulmonary pleomorphic carcinoma that metastasized to the jejunum in an 80-year-old woman. The patient was admitted to the hospital with symptomatic anemia and melena that had been ongoing for several months. In 2021, non-small cell carcinoma was diagnosed by fine-needle aspiration. In 2022, a computed tomography (CT) scan revealed an enormous mass in the small bowel. The tumor was resected and showed pleomorphic neoplastic cells with giant and spindle cell morphology. These neoplastic cells were positive for thyroid transcription factor 1 (TTF1). Next-generation sequencing of the secondary tumor revealed 97% genomic similarities to the lung tumor and high expression of programmed cell death ligand 1 (PD-L1). The patient may benefit from immune checkpoint therapy.