Diagnosis of Dual Malignancy by 18F-FDG PET/CT in the Setting of Paraneoplastic Cerebellar Degeneration.

We describe a rare case of paraneoplastic cerebellar degeneration (with detectable antineuronal antibody anti-Yo) in which (18)F-FDG PET/CT aided in the detection of 2 synchronous malignancies (one thyroid cancer and the other breast cancer). Interestingly, the primary breast malignancy was non-(18)F-FDG-avid and was detected through the presence of a metastatic (18)F-FDG-avid axillary lymph node. Surgery for both was undertaken in the same sitting, and there was improvement of the neurologic features soon after the surgical removal of the malignancies.