FDG PET/CT in assessment of pulmonary lymphangitic carcinomatosis

The purpose of this study was to assess the role of PET/CT in the diagnosis of pulmonary lymphangitic carcinomatosis.

Integrated PET/CT images of 35 patients (15 men, 20 women; mean age, 64.5 years) with pulmonary lymphangitic carcinomatosis confirmed at follow-up chest CT or histopathologic examination were analyzed retrospectively. Standardized uptake value based on body weight and the initial injected activity was measured in the affected lung, the normal lung, and the mediastinal blood pool. Two radiologists independently assessed abnormal PET activity in the lungs. Both radiologists reviewed the CT images to determine the presence, size, location, and extent of pulmonary lymphangitic carcinomatosis. The data were analyzed to determine the sensitivity and specificity of PET for pulmonary lymphangitic carcinomatosis.

Among the 35 patients with pulmonary lymphangitic carcinomatosis, 17 (49%), 13 (37%), and five (14%) patients had diffuse, focal, and bilateral pulmonary lymphangitic carcinomatosis, respectively. Thirty of the 35 patients had nodular septal thickening as the chief CT finding of pulmonary lymphangitic carcinomatosis. Subjective assessment showed a visually identifiable increase in uptake in the region of pulmonary lymphangitic carcinomatosis in 30 of the 35 patients (86%). Four of the other five patients had focal pulmonary lymphangitic carcinomatosis, and one patient had diffuse pulmonary lymphangitic carcinomatosis of the right lung. The specificity of PET/CT for pulmonary lymphangitic carcinomatosis was 100%, and the sensitivity was 86%. The mean standardized uptake value in the region of pulmonary lymphangitic carcinomatosis (1.37+/-0.64) was significantly greater than that in normal lung (0.51+/-0.29) (p<0.0001). The standardized uptake ratio of mediastinal blood pool to lymphangitic lung was 1.26+/-0.45, and that of blood pool to normal lung was 3.78+/-1.37.

FDG PET/CT has high specificity in the detection of pulmonary lymphangitic carcinomatosis. Focal pulmonary lymphangitic carcinomatosis close to a primary malignant tumor, however, can be missed at PET.