Signet ring cell adenoma of the thyroid with mucin predominance.

A 22-year-old male presented with a 1-year history of a right anterior neck mass. He did not have gastrointestinal cancer. Laboratory examination revealed an elevated serum thyroglobulin level of 120 ng/mL. The neck lesion showed poor uptake on 99mTc scan, but enhanced uptake on 201T1 scan. The patient underwent a hemithyroidectomy; the cut surface of the 7 x 3.5 cm lesion was solid and tanned orange. Postoperatively the serum thyroglobulin level decreased to 26 ng/mL. Microscopy of the tumor showed signet ring cells and microfollides, both of which were positive for mucicarmin and alcian Blue. A small percentage of the follicles were positive for thyroglobulin and periodic acid-Schiff. Our literature search detected 18 patients with signet ring cell lesions positive for thyroglobulin, but none had characteristics similar to ours showing predominance of mucin and poor staining for thyroglobulin.