Primary Enteric Adenocarcinoma Lung with Mesenchymal Epithelial Transition Factor Amplification: A Case Report.

Introduction: Primary enteric adenocarcinoma (PEAC) of the lung is a rare variant characterized by the presence of colorectal adenocarcinoma like components. A rare case of PEAC of lung with over-expression of mesenchymal epithelial transition factor (MET) receptor tyrosine kinase protein is being presented.

Case Report: A 75-year old female presented with chest pain, cough, hemoptysis and fever for 2 months duration. Computerized tomography (CT) scan revealed a spiculated mass in left upper lobe of lung. A needle core biopsy was performed. The histopathological examination revealed a tumor composed of tall columnar cells with vesicular nuclei arranged in an acinar and glandular formation with luminal necrosis. On immunostaining, cytokeratin 7, thyroid transcription factor 1 and CDX-2 were positive. Based on the morphological and immunostaining profile a diagnosis of PEAC of the lung was rendered. Ancillary testing for driver mutations revealed over expression of c-MET while epidermal growth factor receptor (EGFR) mutations, anaplastic lymphoma kinase (ALK) rearrangement and C-ros oncogene 1, receptor tyrosine kinase (ROS 1) were negative.

Discussion: PEAC of the lung which was first described by Tsao and Fraser, is an uncommon variant and rarely harbors any driver mutations. MET over expression is present in 3-7% cases of lung adenocarcinoma and is indicative of aggressive tumor behavior. Colo-rectal adenocarcinomas with MET amplification have poor overall survival. The histogenesis of PEAC may be implicated to the dysregulation of MET pathway. Targeted therapy using MET inhibitors in cases that have MET amplification has predictive implications.

Conclusion: This is a rare case of PEAC with c-MET over expression. The MET axis that is implicated in pathogenesis of colonic adenocarcinomas might also be the molecular pathway for the development of PEAC.