Intense 18-fluorodeoxyglucose uptake by the thymus on PET scan does not necessarily herald recurrence of thyroid carcinoma.
This is the first report of intense fluorodeoxyglucose positron emission tomography (FDG-PET) uptake secondary to thymic hyperplasia during follow-up for thyroid carcinoma. A 36-yr-old woman underwent thyroidectomy for a papillary carcinoma measuring 4 cm in diameter. After two doses of radioiodine, thyroglobulin (Tg) remained detectable following recombinant human TSH (rhTSH) stimulation. A whole body scan (WBS) was negative. On computed tomography (CT) scan, a slightly lobulated thymus was visualized. PET scan showed intense thymic uptake. Following resection, anatomo-pathological analysis showed homogenous hyperplastic thymic gland without neoplastic cells. Two months later, under levothyroxin (L-T4) substitution, Tg was no longer detectable and PET scanning did not show any 18-FDG uptake. This observation suggests that thymic FDG uptake does not necessarily herald recurrence of thyroid carcinoma and must be interpreted with caution in such a setting. Other conditions associated with abnormal uptake by hyperplastic thymus must also be envisaged.
Godart
V
V
Department of Endocrinology, Université Catholique de Louvain, St-Luc University Hospital, Brussels, Belgium.
Weynand
B
B
Coche
E
E
De Nayer
P
P
Daumerie
C
C
D000328:Adult; D002291:Carcinoma, Papillary / Q000097:blood / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007457:Iodine Radioisotopes; D009364:Neoplasm Recurrence, Local / Q000473:pathology*; D019275:Radiopharmaceuticals; D013950:Thymus Gland / Q000000981:diagnostic imaging*; D013954:Thyroglobulin / Q000097:blood; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000494:pharmacology; D013974:Thyroxine / Q000494:pharmacology; D014055:Tomography, Emission-Computed
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine