Endocrine Abstracts

Introduction: Medullary thyroid carcinoma (MTC) arises from thyroid parafollicular C cells and accounts for <5% of thyroid cancers. Nearly 25% occur in the context of multiple endocrine neoplasia type 2 syndrome (MEN2) or familial isolated MTC.

Objectives: Evaluation of clinical characteristics and evolution of patients with MTC.

Methods: Retrospective analysis of clinical records of patients with MTC diagnosed from 2001 to 2023.

Results: 42 cases of MTC were identified. 27 (64%) were female. Mean age at diagnosis was 46.2±2.8 years (10-78). 35.7% of patients presented symptoms, mostly cervical swelling; two had diarrhea. 8 patients (19%) had a germline mutation in the RET proto-oncogene. 40 underwent total thyroidectomy, 6 of them in two surgical stages; 2 performed only lobectomy. 33.3% (n=14) had lymph node dissection - 5 of the central compartment, 9 central+ipsi/bi-lateral. 5 MEN2A patients performed prophylactic thyroidectomy. The median tumor size was 1 mm, 19% (n=8) being microcarcinomas. The most frequent location was the right lobe (42.9%); 33.3% (n=14) were multifocal. The remaining thyroid parenchyma exhibited nodular hyperplasia in 23.8% (n=10), chronic lymphocytic infiltration in 28.6% (n=12) and synchronous papillary microcarcinomas in 14.3% (n=6). Resection was R0 in most patients (90.5%). Nodal involvement was present in 28.6% (8 N1b and 4 N1a), and distant metastases in 7.1% (n=3). AJCC classification was I, II, III, IVA and IVC in 38.1% (n=16), 28.6% (n=12), 11.9% (n=5), 11.9% (n=5) and 7.1%(n=3), respectively. Response to surgery was excellent in 71.4% (n=30), biochemical incomplete in 16.7% (n=7) and persistent structural disease in 11.9% (n=5). Stage I and II had higher probability of excellent response to surgery (93.8% and 100%, respectively) than stage III (40%) and IV (0%). All but one patient with nodal involvement (n=12) showed persistent disease. Among patients exhibiting excellent response, 5 (16.6%) experienced recurrence - 3 were only biochemical, and 2 MEN2A patients developed structural disease. While 59.5% (n=25) were cured, 35.7% (n=15) still have evidence of biochemical or structural disease. Seven patients (16.7%) required adjuvant therapies, 3 of whom are under tyrosine kinase inhibitors (selpercatinib or vandetanib). Deaths due to MTC occurred in 4.8% (2 patients).

Conclusions: Our center’s outcomes showed a substantial rate of excellent response, especially in stages I-II, highlighting the importance of early detection and intervention. While the cure relies essentially on the surgical response, surveillance is necessary for potential recurrence, especially in MEN2 patients. Long-term clinical studies are vital to enhance our understanding of this rare malignancy.