Is Hashimoto’s thyroiditis a risk factor for medullary thyroid carcinoma? Our experience and a literature review

Abstract

The etiology of medullary thyroid carcinoma remains unknown. The aim of this study was to determine whether there is a significant association between medullary thyroid carcinoma and Hashimoto's thyroiditis in the histopathologic material of thyroidectomized patients. Retrospective cross-sectional study. In this study, we reviewed the medical records of all patients who underwent total thyroidectomy for different thyroid-related complaints between January 2000 and January 2012 at Jordan University Hospital-Amman, Jordan. To highlight relevant previously published studies addressing this topic, a literature search was conducted for English language studies reporting "medullary thyroid carcinoma" or "C-cell hyperplasia" in patients with Hashimoto's thyroiditis. Of the 863 patients with a mean age of 47.2 ± 12.3 years who underwent total thyroidectomy during the study period, 78 (9.04 %) were diagnosed with Hashimoto's thyroiditis, and 15 (1.74 %) had medullary thyroid carcinoma, 3 (20 %) of whom had coexistent Hashimoto's thyroiditis. A total of 683 (79.1 %) patients had benign thyroid disease, 67 (9.8 %) of whom had Hashimoto's thyroiditis. The difference between these rates was not statistically significant (p = 0.19). When examined by gender, 9 females had medullary thyroid carcinoma, 3 (33.3 %) of whom had coexistent Hashimoto's thyroiditis; by contrast, of 560 females with benign thyroid disease, 62 (11.1 %) had Hashimoto's thyroiditis (p = 0.04). Although this study population represents a small and single-institution experience, our results suggest that there might be an association between Hashimoto's thyroiditis and medullary thyroid carcinoma only in female patients who undergo total thyroidectomy.

Association between Hashimoto’s Thyroiditis and Thyroid Cancer in 64,628 Patients

“…Nineteen studies ( n  = 23,848) examined HT among TC (Table 2), and 19 studies ( n  = 41,643) examined TC among HT (Table 3). Of these, 863 patients were included in both analyses (19). …”

“…Among patients with PTC ( n  = 11,155), 18.90% had HT ( n  = 2,108) (16, 19–29, 31–36). The female:male (F:M) ratio was 4.8:1 (7,815:1,623) for PTC patients, and the RR of having HT in PTC patients varied from 0.60 (95% CI 0.29–1.21) to 23.97 (95% CI 6.98–82.29).…”

“…One study ( n  = 863 subjects) examined the association between HT and MTC (19). Among patients with MTC ( n  = 15), 20% had HT ( n  = 3) with a RR of 2.04 (95% CI 0.72–5.75).…”

“…Among patients with HT ( n  = 2,296), 1.26% had FTC ( n  = 29) (19, 38, 43–45, 49, 51, 52). Two studies reported the F:M ratio among patients with FTC to be 2.4:1 (34:14).…”

Thyroid Autoimmunity and Cancer

“…Even though controversial, literature about the linkage between AITDs and TC is wide, while the reports about a potential relationship between AITDs and MTC (or thyroidal C-cells hyperplasia) are nearly anecdotal and -beyond suggestions that can originate from small series or case reports -they do not allow to draw definitive conclusions [30].…”