One of the two cases discussed here was that of a thyroid tumor that had metastasized from the kidney; in the other case,
metastasis was from the colon. Case 1 was that of a 51-year-old woman who had received left nephrectomy for renal cell
carcinoma 3 years earlier. A low-density area was found incidentally in the left thyroid lobe on CT scan performed to evaluate
metastasis to the left clavicle. Subsequent ultrasound examination of the thyroid showed two circumscribed nodules with very
low internal echoes in each lobe. Three nodules appeared extremely hypervascular on color Doppler examination, suggesting
metastasis from renal cell carcinomas. Another nodule was avascular, suggesting that this nodule was a cyst. The diagnosis of
metastasis from renal cell carcinoma was confirmed pathologically, and the ultrasound appearances was considered characteristic of this rare condition. Case 2 was that of a 49-year-old man who had undergone sigmoid colectomy for colon cancer and
cannulation of the hepatic artery for treatment of liver metastasis. The metastatic liver tumors contained calcifications. A hard
mass was palpated on the left side of the neck when hoarseness developed 2 years later. Ultrasound showed an echo-poor mass
in the left thyroid lobe. This mass contained extremely small echogenic spots that probably represented small calcifications.
Multiple cervical lymph-node swelling was also present. The small calcifications suggested metastasis from colon cancer,
although primary thyroid cancer, papillary carcinoma in particular, could not be ruled out. The pathologic diagnosis of the
surgical specimen was metastasis from colon cancer. Ultrasonographic apperarance, which demonstrated characteristics of the
primary tumor and metastasis to the involved organ, was useful in the diagnosis of these two cases.