Follicular Thyroid Carcinoma with Unusual Radioiodine-Refractory Breast Metastasis Mimicking Primary Breast Malignancy

The breast is an unusual site for metastasis from malignant tumors, although it may be the first manifestation of extramammary primary malignancy typically arising in lung, skin (melanoma), ovary, or lymph nodes (lymphoma). Breast thyroid carcinoma extremely rare and take years to develop, as differentiated usually indolent slow-growing metastasizes nodes, lungs, bones. Here, we present case a middle-aged woman (after subtotal thyroidectomy multinodular goiter 24 y previously) showing discordant 18F-FDG iodine avidity proven metastatic disease involving bones, spleen, on whole-body 131I scans due tumor heterogeneity.