Rare Intensely Fluorine-18-fluorodeoxyglucose Avid Large Retropharyngeal Goiter in a Patient with Invasive Breast Carcinoma.

Diffuse increased fluorine-18-fluorodeoxyglucose ((18)F-FDG) avidity on positron emission tomography (PET) scans has been demonstrated in patients with chronic thyroiditis, likely secondary to increased inflammatory cell glucose uptake. A complex association has been demonstrated between breast cancer and thyroid disease, although the mechanism remains elusive. Development of chronic thyroiditis and/or goiter in breast cancer patients has been suggested to convey a more favorable prognosis. Goiter extension is almost exclusively into retrosternal space, with only a handful of cases reported with superior extension into retropharyngeal space. We present a rare case of a diffusely enlarged goiter extending superior and posterior into the retropharyngeal space with an associated intense (18)F-FDG avidity standardized uptake value maximum (SUVmax) of 16.1 in a patient with invasive ductal breast cancer. To our knowledge, this represents the first published case of diffusely (18)F-FDG avid goiter with retropharyngeal extension.