Coexisting CLT in PTC is an independent predictor of tumor aggressiveness for patients aged under 55: a retrospective analysis of 635 patients

BACKGROUND: The study was aimed at investigating the potential role of chronic lymphocytic thyroiditis (CLT) in papillary thyroid cancer (PTC) aggressiveness for patients aged below 55, as well as to figure out factors influencing potential recurrence risk in different age groups. METHODS: A total of 635 adult patients were retrospectively analyzed. 188 patients were diagnosed with coexistent CLT and the remaining 447 were classified as non-CLT. Then the characteristics of CLT-coexisted patients and non-CLT ones were compared respectively when patients were aged ≥ 55 years or below. The association among postoperative clinicopathological features were also analyzed using multivariate regression. In addition, the prognostic value of several variables relating to high-risk recurrence were estimated within different age groups. RESULTS: When divided in two age groups (55 years as the borderline), non-CLT group (aged below 55 years) had a remarkable frequency of small size lesion (D(max) ≤ 1 cm) compared with CLT-coexisted patients (54.6% to 43.0%, p = 0.02). In addition, non-CLT patients tended to have intrathyroidal extension as opposed to those with coexistent CLT (20.2% to 28.2%, p = 0.05). In multivariate analysis, CLT still significantly acted as an independent risk factor of greater lesion size (D(min) > 1 cm) (OR = 1.7, p = 0.02) and mildly promoted gross extrathyroidal extension (ETE) (OR = 1.4, p = 0.06). However, associations didn’t emerge in the characteristics mentioned above with CLT when patients were ≥ 55 years old. The prognostic value of CLT in high-risk recurrence was evident only in patients aged 35–44 years. (OR = 2.4, 95%CI:1.2–5.4, p = 0.02). Greater lesion size independently promoted gross ETE, no matter patients were aged above 55 years or not. Its prognostic value of high-risk recurrence was significant throughout all age groups. CONCLUSION: These findings revealed that CLT coexistence might be the unfavorable factor of PTC aggressiveness in patients aged below 55 years. Its role as well as greater tumor size may potentially predict higher recurrence risk according to results figured out in the prediction model. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12902-022-00945-4.