Metastatic lymph node calcification in rectal cancer: comparison of CT and high-resolution MRI.

Calcification causes mixed signal intensity in the lymph node (LN) on high-resolution magnetic resonance imaging (MRI), which is a strong indicator of regional LN metastasis in rectal cancer. Calcified metastatic LNs in rectal cancer commonly display scattered fine punctate calcifications to varying degrees on computed tomography (CT). On high-resolution MRI, the calcifications manifest a patchy area of signal loss in corresponding calcified area that is larger than on CT. It is necessary to recognize the appearance of metastatic LN calcifications on high-resolution MRI in rectal cancer because it is the primary imaging method for local staging in rectal cancer. This pictorial essay aims to introduce an important imaging finding that can contribute to the diagnosis of LN metastasis by illustrating features and differences between CT and high-resolution MRI of metastatic LN calcifications in rectal cancer.