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 reve aled an elevated serum thyroglobulin level of 120 ng/mL. The neck lesion sh owed poor uptake on Tc-99m scan, but enhanced uptake on Tl-201 scan. The pa tient underwent a hemithyroidectomy; the cut surface of the 7 x 3.5 cm lesi on was solid and tanned orange. Postoperatively the serum thyroglobulin lev el decreased to 26 ng/mL. Microscopy of the tumor showed signet ring cells and microfollicles, both of which were positive for mucicarmin and alcian B lue. A small percentage of the follicles were positive for thyroglobulin an d periodic acid-Schiff. Our literature search detected 18 patients with sig net ring cell lesions positive for thyroglobulin, but none had characterist ics similar to ours showing predominance of mucin and poor staining for thy roglobulin.