Tumor desmoplasia outperforms preoperative serum calcitonin as surgical biomarker in sporadic medullary thyroid cancer.

Background: Conceptually, thyroid tumor desmoplasia may be better suited for excluding node metastases in sporadic MTC than preoperative serum calcitonin levels.

Methods: This analysis included 181 patients with unilateral sporadic MTC graded on the 7-grade desmoplasia scale after thyroidectomy and neck dissection.

Results: When thyroid tumor desmoplasia reached 1% and ≥50%, node metastases increased from 0% to 7% (median of 0 metastases) and 83% (median of 7.5 metastases), microscopic lymphatic invasion from 0% to 3% and 35%, extrathyroid extension from 0% to 5% and 22%, and extranodal growth from 0% to 0% and 44%, whereas biochemical cure declined from 100% to 95% and 25%. Thyroid tumor diameters and basal calcitonin overlapped widely among the seven desmoplasia groups, precluding differentiation by thyroid tumor size or serum calcitonin levels.

Conclusions: Thyroid tumor desmoplasia, unlike serum calcitonin levels, discriminates extremely well between node-negative and node-positive sporadic MTC, opening new avenues for precision surgery.