Coexistence of Papillary Thyroid Carcinoma in Secondary Hyperparathyroidism

Abstract Background: Coexistence of primary hyperparathyroidism and papillary thyroid carcinoma is common and may be associative with more aggressive papillary thyroid carcinoma for higher rates of extrathyroidal extension and multicentricity. However, it remains unclear whether secondary hyperparathyroidism accounts for more invasive papillary thyroid carcinoma in terms of morbidity, tumor pathological characteristics and prognosis. The aim of this study was to evaluate the rate and tumor characteristics of papillary thyroid carcinoma in patients of SHPT.Methods: A total of 531 patients diagnosed of SHPT and underwent surgery were evaluated retrospectively from January 2013 to December 2018 in the first affiliated hospital of the Zhejiang University. Patients’ demographics, operation records and follow-up information were recorded and analyzed. Among them, 34 patients had PTC concurrent with SHPT (PTC+SHPT) were enrolled. Control subjects were derived through 1:4 matching for age, sex and gender pathological subtype. 136 patients of papillary thyroid carcinoma were selected as control group after matching 1:4 for age, gender and pathological subtype.Results: There were 34 patients coexisting with PTC+SHPT among the 531 surgery patients diagnosed as SHPT (6.4%). Mean tumor diameter of PTC+SHPT group was smaller than that in PTC group(5.57mm vs 9.00mm, p＜0.001). The proportion of papillary thyroid micro-carcinoma in PTC+SHPT group were significantly higher than that in PTC group [29 (85.29%) vs 86 (63.24%), P=0.014]. There were no statistically significant difference among the tumor multicentricity [15 (44.12%) vs 39 (28.68%), P=0.066], tumor bilaterality [9(26.47%) vs29(21.32%), P=0.499]，tumor extrathyroidal extension [2(5.88%) vs19 (13.97%), P=0.255] and lymph node metastasizes rate [12 (35.29%) vs 49 (36.03%), P=1.000]. We found differences between PTC+SHPT group and PTC group patients with respect to contralateral thyroidectomy [10 (29.41%) vs 70(51.47%), P=0.023] and lymph node dissection [22 (64.71%) vs 125(91.91%), P＜0.001].There was no significant difference between PTC+SHPT group and PTC group in prognostic staging [33 (97.06%) vs 122 (89.71%), P=0.309] and recurrence [mean follow-up time 36 months vs 39 months, P=0.33].Conclusions: The prevalence of PTC is high in patients with SHPT. Compared with PTC in the general population, most of PTC with SHPT are occult thyroid carcinoma and present no significant difference in tumor pathological features and prognostic staging. It is necessary for surgeons to make more adequate preoperative prediction and do more careful examination during the surgery in case of missing the coexistence of PTC in SHPT patients.