Correct!
3. The thoracic MR shows that the lesion does not enhance significantly
The thoracic MR shows the same subcarinal mass seen at CT, but adds additional information regarding the subcarinal lesion’s tissue components. The subcarinal lesion does show increased signal intensity on the T1-weighted images, which is common with fat (note the hyperintense signal of subcutaneous fat on these images); however, the lesion continues to show hyperintense signal on MR sequencing employing fat saturation, indicating that the internal hyperintensity of the lesion is not due to fat. Fat saturation refers to MR techniques designed to eliminate signal from fat. When a lesion shows high signal on T1-weighted imaging, suggesting the possibility of intralesional fat, if that signal disappears when using fat-saturation techniques, then one can be relatively certain that the hyperintensity of the lesion on T1-weighted imaging is not due to the presence of intralesional fat; rather, the increased signal could be due to other causes of hyperattenuation on T1-weighted imaging, particularly hemorrhage or proteinaceous fluid. The increased signal on the triple inversion recovery images (which is a sequence designed to show increased signal within fluid- note the hyperintensity of the cerebrospinal fluid posteriorly) suggests the possibility of a cyst, but some solid lesions can display this behavior as well, so the lesion cannot be characterized as a cyst on this sequence alone. However, the images obtained before and after intravenous contrast administration, which show no evidence of enhancement, combined with the fluid signal on the triple inversion recovery sequences, are consistent with a cystic mediastinal lesion in the subcarinal space. The thoracic MR study shows no other sites of abnormality.
Which of the following represents the next most appropriate step for the evaluation of this patient? (Click on the correct answer to proceed to the sixth of seven panels)