Thyroid C-cell hyperplasia shown by combined In-111 pentetreotide, Tc-99m pertechnetate, and Tc-99m MIBI scintigraphy

A patient with a previous diagnosis of colorectal adenocarcinoma presented with increased chromogranin A. In-111 pentetreotide whole body scan revealed an area of intense homogeneous uptake in the right thyroid lobe. A "cold" area, corresponding to the nodule was detected by Tc-99m pertechnetate thyroid scintigraphy (PTS). Two US-guided FNA biopsies indicated that the lesion was benign, whereas it appeared to have a malignant potential in functional imaging studies. Tc-99m Sestamibi thyroid scintigraphy was indicative of cellularity increasing the likelihood of malignancy. Calcitonin-specific stain on the removed nodule revealed some strongly-stained parafollicular elements. Final diagnosis was neoplastic C-cell hyperplasia, which is thought to precede sporadic medullary thyroid carcinoma.