Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor arising from parafollicular C cells of the thyroid, accounting for 1–2% of thyroid malignancies. Total thyroidectomy is the cornerstone of treatment; however, disease recurrence or persistence is not uncommon, particularly when biochemical markers remain elevated despite prior surgical intervention. This case highlights the diagnostic and management complexities of MTC recurrence in the context of prolonged loss to follow-up and limited access to advanced diagnostics.

A 56-year-old female with a known history of medullary thyroid carcinoma diagnosed in 2013, previously treated with total thyroidectomy, presented after being lost to follow-up for several years. Recent evaluation revealed persistently elevated serum calcitonin (5,831 pg/mL) and CEA (422.6 ng/mL). Fine-needle aspiration biopsy of a left cervical lymph node confirmed metastatic carcinoma. Cross-sectional imaging demonstrated enlarged cervical lymph nodes and a stable enhancing nodule in the left thyroid bed, suggestive of locoregional recurrence. There was no radiologic evidence of distant metastases. PET imaging was advised but remains pending due to financial constraints. Multidisciplinary discussions have been initiated regarding the timing and extent of potential surgical re-intervention.

This case illustrates the utility of biochemical surveillance (calcitonin and CEA) as sensitive markers for detecting MTC recurrence, even in the absence of clear radiographic progression. It also highlights the importance of long-term follow-up, particularly in patients with known high-risk histology. The delayed return to care and limited access to PET imaging complicate management decisions, emphasizing the need for adaptable surveillance strategies and multidisciplinary coordination. Persistent disease without definitive distant spread raises questions about the optimal timing for reoperation and the role of systemic therapy.

Persistent elevation of calcitonin and CEA in MTC should prompt thorough investigation for residual or recurrent disease. In resource-constrained settings, clinicians must rely on available imaging, clinical judgment, and coordinated care to guide management. This case underscores the critical role of continuous follow-up and the challenges encountered when surveillance is interrupted.