Endocrine Abstracts

Introduction: Classically, risk stratification in papillary thyroid carcinoma (PTC) assigned the same magnitude of risk to all patients with regional lymph node involvement (N1 disease). However, specific lymph node characteristics (such as size, number, extension, etc.) will allow individualizing treatment and follow-up. One-Step Nucleic Acid Amplification (OSNA) measures the number of copies of mRNA of cytokeratin 19 (CK19) as a marker of lymph node metastasis. Thus, copy numbers between 250 and 5000 were considered micrometastases (mM1), and more than 5000 copies were designated as macrometastases (MM1).

Objective: To analyze the influence of OSNA lymph node metastasis classification in the histological characteristics of PTC in patients submitted to lymph node dissection (LND).

Material and methods: LND from 40 patients (28 female, mean age 49±15 years old) were evaluated. Lymph node metastases were detected using OSNA. Metastases characteristics include total tumoral load (TTL), TTL per total lymph node weight (TTL/TLNW), and mM1 versus MM1. According to the metastases status tumor related variables were studied.

Results: A total of 513 lymph nodes were found, with a mean (S.D.) of 12.8 (9.5) per patient. Thirty LND were considered positive for metastases (75%). There were no significant differences in tumor histological variables and TTL or TTL/TLMW. According to mM1 versus MM1 status, there were 10 (25%) patients with no lymph node involvement, 11 (27.5%) with only mM1, and 19 (47.5%) with at least one MM1. Only this last group was significantly related with primary tumor size (P=0.04), vascular invasion (P=0.03), extrathyroidal extension (P=0.04) and positive margin (P=0.04).

Conclusion: Lymph node macrometastases detected by OSNA are related with more aggressive PTC. OSNA could be a useful technique to improve lymph node metastases characterization.