Invasive mucinous adenocarcinoma of the lung is a rare disease with distinct pathological features and uncommon biological manifestations. We report a 50 year-old woman who initially presented with increasing shortness of breath and progressive facial swelling. She was diagnosed with invasive mucinous adenocarcinoma of the lung with its immunohistochemistry revealed as CK7 (+), CK20 (+), CDX2 (+), TTF-1 (-), CK5/6 (-), and P63 (-). We also describe how the patient initially had a good response to chemotherapy with paclitaxel and cisplatin.