Endocrine Abstracts

Introduction: Medullary thyroid cancer (MTC) is a rare tumour. Mostly sporadic, 25% are associated with multiple endocrine neoplasia (MEN2A/B) or isolated familial MTC. Surgery is the only curative option: its response is defined as complete (no evidence of biochemical or structural disease), incomplete (only structural response) and persistence of structural disease. We aimed to analyse the clinical and pathological factors associated with the prognosis of MTC.

Materials and Methods: Retrospective analysis of clinical and pathology records from MTC cases in a tertiary centre from 2001-2023. Surgical response was assessed through cervical ultrasound and calcitonin 6 months postoperatively. Histopathological reports included tumour size, uni-/multifocality, margin distance, C-cell hyperplasia, coagulative necrosis, and linfovascular invasion. The remaining parenchyma was assessed for nodular hyperplasia or chronic lymphocytic infiltration.

Results: From 42 patients, 64% (n=27) were female. Mean age at diagnosis was 46.2±2.8 years. Mean follow-up duration was 12±1.1 years. 35.7% presented symptoms at diagnosis (mostly cervical swelling); two had diarrhoea (both with distant metastases). 19% (n=8) had a RET germline mutation, 5 of whom performed a prophylactic thyroidectomy. Surgery resulted in excellent response in 71.4% (n=30), biochemical incomplete response in 16.7% (n=7) and persistent structural disease in 11.9% (n=5). Among patients with excellent response, 16.6% (n=5) experienced recurrence, 3 were only biochemical. Male patients were more likely to have persistence of structural disease after surgery (35.7%), P=0.003. Multifocal MTC showed less complete response rates (46.2% vs 82.1% in unifocal MTC), P=0.029. Only 30% of patients with linfovascular invasion in the histopathology report exhibited a complete response to surgery (P=0.003). All patients with nodular hyperplasia showed complete response post-surgery, compared to those with chronic lymphocytic infiltration (75%) or thyroid parenchyma without these alterations (55.6%), P=0.041. Coagulative necrosis was present in 2 patients and was associated with persistence of structural disease (P=0.012). Tumours that touched the thyroid margin showed a poorer response to surgery (P=0.021). Higher recurrence was associated with RET germline mutation (P=0.04) and with T staging at diagnosis (P=0.009). Thirty-nine patients are alive: 61.5% (n=24) cured; 38.5% (n=15) with disease persistence. N staging at diagnosis associated strongly with disease persistence (P<0.001). 3 patients died, 2 due to MTC.

Conclusion: An incomplete response to surgery, whether biochemical or structural, was associated with male gender, multifocal MCT, linfovascular invasion and coagulative necrosis. Adjacent nodular hyperplasia associated with better response to surgery. Higher recurrence was associated with RET germline mutation and with T staging at diagnosis.