In the January 12, 1998, issue of the ARCHIVES, "Autopsy and Medicine" Case of the Month series1 and the subsequent letter "Pulmonary Arterial Carcinomatosis vs Pulmonary Embolism" by Dr Johnson,2 the discussion appears incomplete to me. The well-known disease entity formerly known as lymphangitic pulmonary metastases (LPM) (which seems to have disappeared from most text books) was and continues to be characterized clinically by severe respiratory insufficiency with hypoxemia, pathologically by widespread lymphatic metastases, and radiologically by bilateral reticular infiltrates. In 1971, Janower and Blennerhassett3 showed that patients with LPM had tumor emboli in the pulmonary arterial vasculature, which was probably responsible for the severe physiological abnormalities present in this condition. They suggested the LPM—commonly associated with reticular infiltrates on chest films—occurs secondary to tumor embolization. Pulmonary arterial carcinomatosis microemboli (PACME) leads sequentially to LPM. Chest x-ray films may not show abnormalities in the former and abnormalities in the latter. We showed this in a report over 20 years ago.4 We also pointed out that like ordinary pulmonary embolism, LPM—or more specifically, its precursor, PACME—could be associated with abnormalities seen on perfusion lung scans in the face of normal chest radiographs.4 Ventilation-perfusion lung scanning can be a powerful tool in PACME, whereas high-resolution computed tomographic lung scanning is very useful in LPM to detect early linear-reticular infiltrates. Failure to appreciate the important research by Janower and Blennerhassett,3 ie, the evolving of LPM from PACME, may cause considerable confusion for internists, oncologists, pathologists, and radiologists (as well as those involved in medical nomenclature).