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.

BACKGROUND: While primary tumor desmoplasia is a powerful biomarker of node metastases in sporadic medullary thyroid cancer (MTC), information for hereditary MTC is sparse.
METHODS: This proof-of-concept study, comprising 3 consecutive children with multiple endocrine neoplasia 2B, evaluated simultaneously the metastatic behavior of multiple primary thyroid tumors of disparate size and extent of desmoplasia within patients.
RESULTS: Altogether, MTC typically involved the ipsilateral central neck before spreading to the ipsilateral lateral and the contralateral neck. Medullary thyroid cancer in the upper thyroid lobe leaped the ipsilateral central neck to invade the ipsilateral lateral neck. Unlike the desmoplasia-positive 6-mm high-grade and 7-mm low-grade primary thyroid tumors, the desmoplasia-negative 8-, 11-, and 16-mm low-grade primary thyroid tumors did not spread to ipsilateral neck nodes. With extranodal growth, the extent of nodal desmoplasia was greater than with intranodal growth.
CONCLUSIONS: This proof-of-concept study suggests that primary tumor desmoplasia is an equally powerful biomarker of node metastasis in hereditary MTC.