Endocrine Abstracts

JOINT3237

Background: Medullary thyroid carcinoma (MTC) is a neuroendocrine tumour originating from parafollicular C cells, with both sporadic and hereditary forms. Early detection is crucial due to its metastatic potential. Serum calcitonin is a key biomarker for MTC, often identifying cases before clinical symptoms arise. Given its autosomal dominant inheritance in hereditary cases, genetic screening plays a pivotal role in at-risk individuals.

Case Presentation: A 41-year-old woman seeking pregnancy consultation underwent thyroid ultrasound, revealing a 5×3.3 mm nodule with vague margins, hypoechoic echotexture, microcalcifications, and peripheral vascularization. Thyroid function was normal. Fine-needle aspiration returned a Bethesda V classification, suspicious for MTC. Serum calcitonin was 16 pg/mL. Family history revealed her paternal aunt and cousin had confirmed MTC, and her father had undergone a thyroidectomy two decades prior with unknown histology. A prior ultrasound a year earlier had categorized the nodules as TIRADS 1, but no family history was elicited at that time, delaying suspicion of hereditary MTC. The patient underwent total thyroidectomy. Histopathology was inconclusive, prompting immunohistochemical analysis, which confirmed MTC in the 5×3.3 mm nodule, positive for calcitonin, carcinoembryonic antigen (CEA), and thyroid transcription factor-1 (TTF-1). The final staging was pT1aN0M0R0. Postoperatively, serum calcitonin and CEA levels were undetectable. Genetic testing for RET mutations was recommended, and first-degree relatives were advised to undergo screening.

Discussion: This case underscores the critical importance of serum calcitonin measurement and family history assessment in thyroid nodule evaluation. Small nodules, often considered clinically insignificant, may harbour malignancy. The presence of microcalcifications in even tiny nodules should raise suspicion, warranting further investigation. Routine calcitonin screening facilitates early MTC detection, optimizing patient outcomes. Given hereditary MTC’s autosomal dominant inheritance, timely genetic screening and family member evaluation is essential to prevent delayed diagnosis and improve prognosis.

Conclusion: Small thyroid nodules, particularly those with microcalcifications, should not be overlooked, as they may indicate hereditary MTC. Integrating calcitonin measurement, thorough family history assessment, and genetic testing into routine thyroid evaluations is crucial for early detection and timely intervention, improving patient management and familial risk assessment.