The lungs are among the most common sites for metastases from a multitude of cancers. The majority of pulmonary metastases appear nodular on radiologic images. Interstitial spread of tumor through pulmonary lymphatics, also known as pulmonary lymphangitic carcinomatosis (PLC), is not uncommon and constitutes approximately 7% of pulmonary metastases. PLC is most often seen with adenocarcinoma of a variety of histologies such as thyroid carcinoma, and melanoma. It is usually noted in late stages of malignancy and therefore is indicative of a poor prognosis. Diagnosis of PLC is usually based on a combination of clinical and radiologic findings. However, the diagnosis is difficult when patients have limited clinical findings or have a history of or the possibility of other interstitial lung diseases. High-resolution computed tomography (HRCT) has been the modality of choice in the radiologic diagnosis of PLC. Imaging features of PLC on HRCT include thickening of interlobular septa, fissures, and bronchovascular bundles. Distribution of PLC may be focal or diffuse, unilateral or bilateral, and symmetric or asymmetric. Although FDG-PET has been extensively used in primary or secondary lung malignancies, its role and appearance in PLC have not been well determined in the literature. In this communication, we describe a spectrum of FDG-PET and CT findings in 5 cases with PLC. Similar to CT, the distribution of PLC can be extensive or limited on the FDG-PET. Diffuse, lobar, or segmental FDG uptake in the lungs is seen in extensive PLC. In limited PLC, a linear or a hazy area of FDG uptake extending from the tumor can be seen. Recognition of various patterns related to PLC on FDG-PET may allow accurate diagnosis of disease and could potentially influence the management of these patients.
From the *Division of Nuclear Medicine, Department of Radiology, Hospital of University of Pennsylvania, Philadelphia, PA; the †Division of Nuclear Medicine, Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA; and the ‡Department of Medical Imaging, A. I. duPont Hospital for Children, Wilmington, DE.
Received for publication December 15, 2005; revision accepted July 17, 2006.
Reprints: Gunsel Acikgoz, MD, Division of Nuclear Medicine, Department of Radiology, Hospital of University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104. E-mail: email@example.com