Multilobulated thymoma with an acute angle: a new predictor of lung invasion.

OBJECTIVE: Imaging features of thymomas such as lobulation, infiltration into lung, and adjacent lung abnormality have been associated with lung invasion but are unreliable. The goal of this study was to develop a more objective and reproducible method for predicting lung invasion by thymomas. SUBJECTS AND METHODS: Fifty-four thymomas resected from 2007 to 2017 were included for analysis. Pre-operative CT scans for these thymomas were reviewed, and multiple features were evaluated, including the interface of each thymoma with the adjacent lung. A multilobulated thymoma with at least one acute angle between lobulations was considered suspicious for lung invasion. Two blinded radiologists then tested this hypothesis by reviewing all 54 CT scans and using this single criterion to predict lung invasion. RESULTS: Twelve thymomas invaded the lung. All lung-invasive thymomas were multilobulated. Twenty-nine thymomas had a multilobulated interface with the lung. Multilobulated thymomas were more likely to invade the lung than thymomas with a single lobulation or no lobulation (p = 0.0008). Using the criterion of multilobulation with at least one acute angle between lobulations to predict lung invasion, the two readers achieved a sensitivity of 67-83%, specificity of 93-98%, positive predictive value of 77-89%, and negative predicted value of 91-95%. Nine lung-invasive thymomas also invaded mediastinal structures or disseminated to the pleura. CONCLUSIONS: A multilobulated thymoma with at least one acute angle between lobulations predicts lung invasion with a high degree of accuracy. When lung invasion is suspected, the findings are indicative of a locally aggressive tumor, and the pleura and mediastinal structures should also be closely inspected for invasion. KEY POINTS: • A multilobulated thymoma with at least one acute angle between lobulations is predictive of lung invasion. • Coronal and sagittal reformations and thin sections are helpful in challenging cases. • Lung invasion indicates a locally aggressive tumor, and the pleura and other mediastinal structures should also be closely inspected for invasion.

Utility of gadolinium for identifying the malignant potential of pancreatic cystic lesions.

PURPOSE: To determine if gadolinium is necessary for the diagnosis of a pancreatic cystic lesion (PCL) as benign or malignant by assessing inter- and intra-observer agreement and diagnostic accuracy for the presence of worrisome features/high-risk stigmata on non-contrast MRI compared to MRI with and without contrast, with cytopathology as a reference standard. METHODS: The institutional database was searched to identify consecutive patients that underwent EUS/FNA or surgical resection of an asymptomatic PCL performed from 01/01/2015 to 01/01/2019. Two abdominal radiologists independently evaluated PCLs on MRI with all sequences except for contrast-enhanced sequences followed by a second reading with data from the entire MRI including pre- and post-contrast sequences. Cyst size, growth, and the presence of worrisome features/high-risk stigmata were assessed for each cyst on both datasets. RESULTS: There were 87 patients with 87 pancreatic cysts; 76(87.4%) were benign and 11 (12.7%) were malignant. The presence of any worrisome features/high-risk stigmata for reader 1 was concordant on both MRIs in 95.4% (83/87; k = 0.874) of cases and for reader 2 was concordant in 96.6% (84/87; k = 0.920) of cases. The diagnostic accuracy of the two datasets when the presence of any worrisome feature/high-risk stigmata was predictive of malignancy was identical for reader 1 (AUC = 0.622 for both; p = 1.0) and similar for reader 2 (AUC 0.569 and 0.589; p = 0.08) for both MRI datasets. CONCLUSION: The addition of gadolinium had no significant impact in the diagnosis of a benign versus malignant PCL, with similar intra-observer agreement and diagnostic accuracy for both readers when using contrast-enhanced and unenhanced MRI datasets.

Incidental liver lesions on baseline breast MRI: Outcomes on subsequent abdominal imaging.

PURPOSE: To examine outcomes of incidental liver lesions on baseline breast magnetic resonance imaging (MRI) that were further evaluated with dedicated abdominal imaging. METHODS: Consecutive breast MRI reports from 2011 to 2016 were retrospectively reviewed to identify incidental liver lesions. Only patients without prior breast MRI, without prior abdominal imaging, and with subsequent abdominal imaging were included. Patient demographics, breast MRI indication, and final liver lesion diagnosis were recorded. RESULTS: Of 131 women (mean age 53.8 years), 94/131 (71.8%) underwent breast MRI for extent of disease evaluation, 25/131 (19.1%) for high-risk screening, 11/131 (8.4%) for implant evaluation, and 1/131 (0.8%) for problem-solving. Of 131 liver lesions (6-80 mm), 117/131 (89.3%) were deemed benign on subsequent abdominal imaging; 10/131 (7.6%) probably benign; and 4/131 lesions (3.1%) were confirmed breast cancer metastases. Metastatic liver lesions identified on breast MRI were more likely for women with a current diagnosis of breast cancer than for women without a current diagnosis of breast cancer: 4.3% vs 0%. Similarly, metastatic liver lesions identified on breast MRI were more likely for those with a higher prognostic stage (2 or 3) vs a lower prognostic stage (0 or 1) or no current breast cancer: 11.1% vs 0%. CONCLUSION: Baseline breast MRIs showing incidental liver lesions showed unsuspected liver metastases only in women with a current diagnosis of clinical stage 2 or 3 breast cancer. This suggests breast MRI indication and clinical staging of current breast cancer, if present, can help plan management and decisions to obtain follow-up of liver lesions.