Mondo Description Well-differentiated fetal adenocarcinoma (WDFA) of the lung is a rare, primary, low-grade, bronchopulmonary neoplasm characterized by a well-circumscribed, usually large, pulmonary mass that is histologically composed of glycogen-rich neoplastic glands and tubules that resemble fetal lungs at 10 to 16 weeks of gestation and benign adjacent stroma. It typically presents with chest pain, cough, dyspnea, hemoptysis and/or generalized, non-specific symptoms, such as night sweats, lethargy, poor appetite and weight loss.