HRCT in primary pulmonary lymphoma: can CT imaging phenotypes differentiate histological subtypes between mucosa-associated lymphoid tissue (MALT) lymphoma and non-MALT lymphoma?

Background: Primary pulmonary lymphoma (PPL) mainly comprises mucosa-associated lymphoid tissue (MALT) lymphoma as well as other subtypes of lymphoma. Different phenotypes of PPL demonstrate various high-resolution computed tomography (HRCT) features. We aimed to evaluate the value of HRCT in the diagnosis and differential diagnosis of PPL, especially between MALT lymphoma and non-MALT lymphoma and the correlation between CT and pathological features. Methods: We performed a retrospective analysis on 72 patients with PPL confirmed by pathology between 2007 and 2016. We compared the CT characteristics and correlation with pathological findings between MALT lymphoma and non-MALT lymphoma groups. Results: All 72 patients with PPL were classified into two groups: low-grade MALT lymphoma (MALToma) (56/72) and high-grade non-MALT lymphoma (non-MALToma) (16/72). The latter group consisted of diffuse large B cell lymphoma (8/72), Hodgkin’s lymphoma (3/72), T-cell lymphoma (4/72), and intravascular large B-cell lymphoma (1/72). A total of 168 lesions were analyzed, including 57 cases with multiple lesions and 15 cases with single lesion. The manifestation of four distribution patterns: nodular or mass-like involvement pattern, diffuse interstitial lung disease (DILD) pattern, pneumonia-like consolidative pattern and mixed pattern was not significantly different between MALToma and non-MALToma (all P>0.05). Signs of air bronchogram and CT angiogram occurred significantly more often in individuals with MALToma group than those with non-MALToma (75% vs. 25%, P=0.001; 64.3% vs. 12.5%, P<0.001; respectively). Conversely, the halo sign presented more often in non-MALToma than in MALToma patients (19% vs. 63.6%, P=0.02). In addition, the butterfly sign was only observed in four patients with MALToma. Conclusions: HRCT imaging phenotypes were beneficial in the diagnosis of PPL. Solitary or multifocal nodules/masses and consolidation were the most common imaging patterns. The air bronchogram sign, CT angiogram sign, halo sign, and butterfly sign could be potential to help to differentiate MALToma from non-MALToma.