Occult metastatic lung carcinoma presenting as locally advanced uterine carcinosarcoma on positron emission tomography/computed tomography imaging

Increasingly, positron emission tomography/computed tomography (PET/CT) is being used as a tumor surveillance modality for multiple tumor types. A 73-year-old postmenopausal female with stage IV nonsmall cell lung cancer presented after a PET/CT demonstrated focal uptake in the superior and lateral aspects of the uterus. The patient reported a history of intermittent postmenopausal bleeding and an endometrial biopsy documented uterine carcinosarcoma. Postoperative pathologic review and immunohistochemical staining with thyroid transcription factor-1 revealed metastatic adenocarcinoma consistent with her lung primary in her uterus and adnexa. Our case represents a rare occurrence in which lung cancer has metastasized to multiple female pelvic organs. Increasing use of PET/CT may lead to the discovery of occult metastases masquerading as a second primary malignancy.