Abstract
BACKGROUND: Localized extranodal lymphoma is generally associated with a more favorable prognosis, whereas systemic lymphomas with extranodal involvement tend to indicate poorer outcomes. The lungs are a common site of invasion, and pulmonary lymphoma may exhibit a diversity of imaging manifestations, which can lead to diagnostic challenges. Therefore, this study aimed to comprehensively characterize the imaging characteristics of pulmonary lymphoma and its subtypes and evaluate their potential for predicting treatment response. METHODS: Three observers retrospectively reviewed positron emission tomography/computed tomography (PET/CT) images of patients with lymphoma and recorded the characteristics of the pulmonary lesions. Statistical analyses included Spearman correlation coefficient analysis, the Chi-squared test, and the Fisher's exact test. RESULTS: A total of 136 cases (66 males and 70 females; mean age 54.84±16.66 years) were included. All cases of primary pulmonary lymphoma (PPL) were non-Hodgkin lymphoma (NHL), with mucosa-associated lymphoid tissue (MALT) lymphoma accounting for 88.57%. Diffuse large B-cell lymphoma (DLBCL) was the main subtype in secondary pulmonary lymphoma (SPL), accounting for 50.50%. PPLs typically appeared as consolidations (68.57%) with air bronchograms (62.86%). In contrast, SPL lesions frequently manifested as nodules (76.24%) with homogeneous metabolic distribution (77.23%) and increased metabolic activity in the hilar lymph node (77.23%). Statistical distinctions between PPL and SPL were observed related to lesion size, hilar lymph node involvement, presence of consolidation and air bronchogram signs, metabolic patterns, and target-to-background ratios (TBRs) (P<0.05). Baseline nodular or consolidated lesions and fludeoxyglucose (FDG) distribution patterns were correlated with posttherapy Deauville 5-point scale (5-PS) (P<0.05), although causality could not be inferred. Pleural involvement in PPL was correlated with more favorable treatment response (P=0.001), while the baseline target-to-mediastinal blood pool ratio (TBR(blood)) showed a moderate positive correlation with 5-PS at follow-up (Spearman ρ=0.236; P=0.032). CONCLUSIONS: PPLs and SPLs demonstrate distinct albeit nonspecific PET/CT manifestations, representing preliminary yet inconclusive differentiation value. Several features, including FDG distribution patterns and lesion morphology, correlate with treatment response, but their causal relationship remains undetermined. Pleural involvement in PPL is associated with improved treatment response, while elevated baseline TBR(blood) in SPL correlates with poorer metabolic remission, indicating that baseline PET/CT parameters may have predictive utility. Further validation of these findings is required.