Endocrine Abstracts

Introduction: It is universally accepted that calcitonin (CT), a hormone secreted by the parafollicular cells of the thyroid, is a specific, sensitive and early marker of Medullary Thyroid Carcinoma (CMT), with higher diagnostic accuracy than fine needle aspiration biopsy(FNAB). However, the routine measurement of serum CT during assessment of nodular thyroid disease (NTD) remains controversial due to rarity of this cancer and possible false positive results.

Aim: To evaluate the frequency of hypercalcitoninemia among patients with NTD,the prevalence of MTC in these cases and the concordance with cytologic results.

Methods: We present a retrospective study including patients with measurement of serum CT during investigation of NTD between january 2010 and june 2019. Data regarding cytologic results, performance of surgery and histological diagnosis were collected. Hypercalcitoninemia was established as a serum CT value >10 pg/ml. These patients were categorized, according the CT levels, in 2 groups: G1- serum CT 10–100 pg/ml; G2- serum CT ≥100 pg/ml. Patients with personal or familial history of MTC or MEN-2 were excluded.

Results: In a total of 1124 patients with serum CT levels measured during the study of NTD, 41 (3.6%) had hypercalcitoninemia [G1: 34 (3.0%); G2: 7 (0.6%)]. The FNAB was performed in 34 (82.9%) cases of high levels of CT [G1: 27 (79.4%); G2: 7 (100%)] and a cytologic result sugestive of MTC was found in 4 (11.8%) [G1: 1(3.7%); G2: 3 (42.9%)]. Among those with hypercalcitoninemia, 15 (36.6%) underwent to surgery [G1: 9 (26.5%); G2: 6 (85.7%)] and in 9 (60.0%) it was confirmed the histological diagnosis of MTC [G1: 3 (33.3%); G2: 6 (100%)]. Among these patients, beyond the 4 cases with FNAB compatible with MTC, 1 was submited to thyroidectomy due a MTC metastasis finding, and the remaining had the following cytological results: follicular neoplasm (n = 1), suspicious of papilar carcinoma (n = 1), suspicious of malignancy (n = 1) and benign result (n = 1). The histological diagnosis distribution of the remaining 6 operated patients was as follows: follicular carcinoma (n = 2), follicular hyperplasia (n = 3) and C cells hyperplasia (n = 1) and all cases belonged to G1.

Conclusion: We documented a prevalence of hypercalcitoninemia in NTD of 3.6%, quite similar to data reported in literature. It has been described a MTC rate range from 0.3 to 1.4% in patients with NTD and from 10 to 40% in hypercalcitoninemia status, which is concordant with our results (0.8% and 22%, respectively). Despite the limited number of individuals, serum CT showed higher diagnostic accuracy to MTC than cytologic study and for values of CT ≥ 100 pg/ml, the positive predictive value was 100%.