An Unusual Case of GI Metastasis From Adenocarcinoma of the Lung

Abstract

Malignancies of the lung most commonly metastasize to the lymph nodes, liver, bones, brain and adrenal glands. Lung cancer metastasizing to the gastrointestinal (GI) tract is rare, and even rarer when there is simultaneous involvement of small and large intestines.?Here we present a rare case of secondary GI metastasis from lung origin. 53-year-old male former smoker of 1 pack-a-day for 20 years and no other medical history was seen in the GI clinic with complaints of unexplained 11 pound weight loss and productive cough with greenishred sputum. He denied a history of recent or recurrent infections, and environmental or occupational exposures. Physical exam was remarkable for diminished breath sounds in the left lower lobe. Chest x-ray revealed a mass on the left lower lobe of the lung which was confirmed on high-resolution chest CT. Biopsy was performed showing adenocarcinoma of the lung. The patient received chemotherapy and underwent left lower lobe lobectomy. Six months later the patient returned to the clinic complaining of fatigue and abdominal bloating, and was found to have iron deficiency anemia. He subsequently had endoscopy and colonoscopy showing an ulcerated lesion of the third portion of the duodenum and a mass in the cecum. Histology confirmed adenocarcinoma of lung origin from both biopsy sites. The diagnosis was validated by histology and immunohistochemical staining. Cells were positive for TTF-1 and CK7, consistent with pulmonary origin. Gastrointestinal origin was excluded with the negative results of CK20 and CDX2 staining. The patient was able to resume chemotherapy.? In our case, the GI tract malignancy happened only months after initial presentation, making secondary GI metastasis a more likely diagnosis. Malignant lung and GI lesions may occur at the same time, however when this happens the primary site is often difficult to establish, particularly if both display the same histologic cell type. In such conditions it is important to perform the immunohistochemically staining for TTF-1, to differentiate the primary origin. Clinicians should be aware of this uncommon presentation.