Artifacts, anatomical and physiological variants, and unrelated diseases that might cause false-positive whole-body 131-I scans in patients with thyroid cancer

The whole body 131-I scan remains an important component in the postoperati ve treatment of patients with well-differentiated thyroid cancer. Because n ormal thyroid tissue remnants and residual or metastatic foci of well-diffe rentiated thyroid cancer have the unique ability to concentrate, organify, and store 131-I, the whole body scan provides a depiction of those tissues that can be ablated with therapeutic doses of 131-I, Over time, it has beco me obvious that the whole body scan may also reveal foci of 131-I uptake ow ing to a wide variety of other causes. We provide a detailed pathophysiolog ical classification of the artifacts, anatomic and physiological variants, and nonthyroidal diseases that may give rise to false-positive whole body s cans in postoperative patients with thyroid cancer. These include ectopic f oci of normal thyroid tissue; nonthyroidal physiological sites (eg, choroid plexus, salivary glands, gastric mucosa, urinary tract); contamination by physiological sections; ectopic gastric mucosa; other gastrointestinal abno rmalities; urinary tract abnormalities; mammary abnormalities; serous cavit ies and cysts; inflammation and infection; nonthyroidal neoplasms; and curr ently unexplained causes. This article also provides a detailed review of t he widely scattered English language literature in which these phenomena we re originally described. Copyright (C) 2000 by W.B. Saunders Company.