Secondary lymphoma of the thyroid in 99mTc-pertechnetate scintigraphy.

We present markedly decreased radioactivity in the right on a 99mTc-pertechnetate thyroid image in a patient with secondary lymphoma of the thyroid. At autopsy, the right lobe of the thyroid was replaced by lymphoma tissue. Markedly decreased radioactivity on the images may be explained by lymphoma cell infiltration or replacement of thyroid tissue with a resultant attenuation effect as well as interference of the trapping mechanism of the thyroid folicular cell. While cold areas in a radionuclide scintigram may present difficulties in interpretation, a high index of secondary lymphoma suspicion should be made by a combination of the scintigraphic findings and history of malignant lymphoma.