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Bilateral lung parenchymal involvement is seen in infective as well as noninfective conditions, appearing as focal or diffuse lung disease. PET/CT with FDG helps in characterization (increased glucose utilization is seen by both inflammatory and neoplastic cells). In this article, we describe the spectrum of patterns of FDG uptake and associated CT changes involving bilateral lung parenchyma. Benign conditions described are aspiration pneumonia; pulmonary toxicity by bleomycin; infections, namely, sarcoidosis, miliary pulmonary tuberculosis, and pulmonary nocardiosis; and inflammatory conditions such as pulmonary Langerhans cell histiocytosis and pulmonary alveolar proteinosis. Neoplastic conditions described are bilateral pulmonary metastases and lymphangitic carcinomatosis.

A 55-year-old man with cough, bone pain, and cervical lymphadenopathy underwent both 18F-FDG and 18F-PSMA-1007 PET/CT scans with clinical suspicion of malignant disease. Compared with 18F-FDG PET/CT, 18F-PSMA PET/CT showed intense tracer uptake in the prostate gland, lungs, osteogenic lesions, and multiple lymph nodes. Interestingly, we also found the high tracer concentration of pulmonary lymphangitic carcinomatosis, a very rare form of prostate cancer metastasis to the lung, on 18F-PSMA-1007 PET/CT images.

Two cases of histologically proven lobar pulmonary lymphangitic carcinomatosis are reported in which well-defined sites of accumulation of Tl-201 and Tc-99m MIBI were observed. The combination of Tl-201 and Tc-99m MIBI SPECT can detect the extent of pulmonary lymphangitic carcinomatosis.

A 56-year-old woman status post bilateral mastectomies, chemotherapy, and radiation treatment of breast cancer presented with dyspnea and associated pleuritic chest pain, fatigue, and chest heaviness. Imaging studies including a chest radiograph, lower extremity color Doppler ultrasound, computed tomography pulmonary angiogram, and high-resolution chest CT (HRCT) were all negative. Lung scan revealed contour mapping of the bronchopulmonary segments, a pattern which can be seen in patients with tumor emboli syndrome or lymphangitic carcinomatosis. A pulmonary angiogram with microvascular cytologic sampling revealed no pulmonary embolus but confirmed the presence of malignant cells identical to the patient's breast cancer.

A 46-year-old woman with advanced ovarian carcinoma had progressive dyspnea and was evaluated with ventilation and perfusion lung imaging. A characteristic pattern of multiple branching perfusion defects of a segmental nature on the perfusion scan suggested tumor microembolism and lymphangitic carcinomatosis. However, in this case, this pattern was associated with pulmonary thromboembolism and was documented by the post mortem examination. Pulmonary thromboembolism should be included among the differential diagnoses in a patient with clinical symptoms and a perfusion scan that reveals multiple branching perfusion defects.

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.

The authors describe the findings of perfusion lung scintigraphy in a case of lymphangitic carcinomatosis in a 30-year-old man with recent symptoms of progressive dyspnea, hypoxemia, and thoracic pain. The diagnosis of lymphangitic carcinomatosis was made by transbronchial lung biopsy. The primary tumor was a gastric adenocarcinoma. The appearance on the perfusion scan of multiple tiny perfusion defects in both lungs could be ascribed to biopsy-proved small artery tumor thrombi associated with lymphangitic carcinomatosis.