Hashimoto's thyroiditis revisited: The association with thyroid cancer remains obscure

Hashimoto's thyroiditis (HT) is an autoimmune disease of the thyroid associated with goiter and hypothyroidism. Although there exists a clear association between HT and lymphomas of the thyroid, the association between HT and thyroid cancer remains unclear. To evaluate this further, we retrospectively reviewed the pathology reports for all thyroidectomy specimens as well as the records of patients admitted to the University of Michigan Medical Center, Ann Arbor, Michigan, U.S.A., over a 10‐yearperiod (1975–1985) with the diagnosis of HT or chronic lymphocytic thyroiditis (CLT). Eight hundred and nine pathologic diagnoses were recorded for 816 thyroidectomy specimens from 793 patients. Furthermore, 180 of 228 patient chart records were available for review. Only 128 patients satisfied our criteria for the diagnosis of HT. HT or CLT were diagnosed in 147 (18.2%) of 809 thyroid specimens. HT occurred concurrently with thyroid cancer in 24% of all cases of HT, whereas, HT occurred concurrently with benign thyroid disease in 71% of all cases of HT in all thyroid specimens. Furthermore, HT was associated with 43 (22%) of 195 cases of thyroid cancer. There were 111 (87%) women and 17 (13%) men of 128 patients whose charts were reviewed. The mean age was 49±14 years. Ninety‐eight (77%) of the patients presented with goiters and 57 (45%) presented with dominant thyroid masses, 38 (67%) of which were solitary nodules. One patient (0.8%) presented with a recurrent laryngeal nerve palsy (RLNP) and 12 (9%) presented with tracheal compression. Only 29 (38.2%) of 76 patients measured had positive antithyroglobulin (ATG) titers, whereas 65 (87%) of 75 patients measured had positive antimicrosomal (AM) titers. Seventy (55%) patients were evaluated with either a technetium or 131 I thyroid scan. There was a heterogeneous pattern to the scan in 75% of these patients. Niney‐one (71%) patients were initially treated with thyroid suppression. However, 27 (21%) required thyroidectomy for initial management. Ultimately, 60% required thyroidectomy and 37% required none. The major indication for surgical intervention was the presence of a dominant mass in 40 (52%) of 77 patients. Only 17 (13%) patients were found to have thyroid cancer concomitant with HT and 3(2%) had lymphoma with HT. The incidence of minimal (occult) cancer in a study of 100 consecutive autopsies at this institution was 13%. We believe that these data suggest that the association of HT with thyroid cancer is relative, at best. It will be necessary to prospectively follow both a large group of patients with HT and a control group of patients without HT for the incidence of thyroid cancer in each before this issue can be appropriately addressed.