Possible pathological basis for false diagnoses of lymph nodes by USPIO-enhanced MRI in rabbits.
OBJECTIVE
To determine the cause of misdiagnosis of lymph nodes in ultrasmall superparamagnetic iron oxide (USPIO) enhanced magnetic resonance imaging (MRI) using histological findings in rabbit tumor and inflammatory models.


METHODS
Thirty-six rabbits were randomly divided into inflammatory and tumor groups. MRI of the popliteal fossa was performed before and 24 hours after USPIO administration. Diagnoses of popliteal lymph nodes were evaluated based on dedicated criteria and were compared with histological and electronic microscopic findings.


RESULTS
There were 46 inflammatory and 26 metastatic lymph nodes. Sensitivity, specificity, and positive and negative predictive values of the diagnosis of nodal metastasis were 84.6%, 87.0%, 78.6%, and 90.9%, respectively. There were four false-negatives with subcapsular metastatic foci and six false-positives with predominant cortex and paracortex hyperplasia. Electron microscopy showed that in inflammatory nodes, cytophagic bubbles contain many USPIO particles, while in metastatic nodes they contained predominantly cellular residues.


CONCLUSIONS
Diagnosis of lymph node malignancy is largely determined by the location and number of metastatic tumor cells. A profound understanding of the physiological role of macrophages in nodes with tumor burden will contribute to better diagnoses for clinical application.
Lei
Jing
J
Department of Radiology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College.
Xue
Hua Dan
HD
Li
Zhuo
Z
Li
Shuo
S
Jin
Zheng Yu
ZY
D000818:Animals; D003287:Contrast Media / Q000494:pharmacology*; D003911:Dextrans / Q000494:pharmacology*; D005295:Ferrocyanides / Q000494:pharmacology; D052203:Ferrosoferric Oxide / Q000494:pharmacology*; D007091:Image Processing, Computer-Assisted; D007249:Inflammation; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D008854:Microscopy, Electron / Q000379:methods; D009362:Neoplasm Metastasis / Q000175:diagnosis; D011237:Predictive Value of Tests; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D003287:Contrast Media; D003911:Dextrans; D005295:Ferrocyanides; D058185:Magnetite Nanoparticles; C097921:ferumoxtran-10; C000170:ferric ferrocyanide; D052203:Ferrosoferric Oxide