In this issue of CHEST (see page 2273), Kamigaki and colleagues describe a small cell lung cancer (SCLC) that presented as an intraluminal lesion in the left descending pulmonary artery. The diagnosis was based on histologic descriptions of transbronchial aspirates that were supported by immunohistochemical data (+thyroid transcription factor-1, +cytokeratin, and –leukocyte common antigen). The results of staining with both chromogranin and synaptophysin were negative, and this indeed may be the case in a small number of SCLCs. Supporting the diagnosis were elevated levels of Pro-gastrin-releasing peptide, neuron-specific enolase, and carcinoembryonic antigens. The weight of evidence suggests that the tumor is an SCLC.