Pulmonary carcinomatous lymphangitis is a form of neoplastic metastatic spread to the lungs, which represents a poor prognosis for the patient. The physician may be confronted by a differential diagnosis with diffuse pulmonary interstitial affections requiring specific treatment, including lung transplantation. We present the case of a patient, diagnosed with pulmonary interstitial disease with rapidly progressive worsening of lung function, who was considered for lung transplantation. Videothoracoscopic lung biopsy demonstrated the existence of carcinomatous lymphangitis, which completely changed the therapeutic direction.