Primary thyroid lymphoma associated with metastatic thyroid tumor: discrimination with US.

We surgically treated a 75-year-old man who suffered from metastatic adenocarcinoma from the colon associated with primary thyroid lymphoma measuring 1 cm maximum in diameter. Radiologic findings were correlated with histopathology of excised specimens. Ultrasonography could discriminate between these two tumors based on the margin characteristics and the lesion echogenicity: the metastatic tumor was shown as an ill-defined hypo to iso echoic mass, while the malignant lymphoma was detected as a well-defined markedly hypoechoic mass. In addition, we could confirm that early-stage primary thyroid lymphoma even as small as 1 cm shows the same radiologic appearance as that of a bulky lymphoma. Copyright 1998 Elsevier Science Ireland Ltd. All rights reserved.