Endocrine Abstracts

Background: Papillary thyroid microcarcinoma (PTMC) is a papillary thyroid cancer (PTC) type with a maximum diameter of ≤ 10 mm. Generally, PTMCs have good prognosis and low mortality risk. However, there are cases of PTMCs showing more biologically aggressive characteristics, such as lymph node (LN) involvement and distant metastasis.

Objectives: Reveal the factors affecting the prognosis and aggressiveness of PTMCs.

Methods: Retrospectively a total of 255 patients over the age of 18 operated on thyroid, at Ondokuz Mayıs University Faculty of Medicine between June 2008 and December 2021, whose pathology results reported as PTMC (maximum tumor diameter of ≤ 10 mm), undergoing regular follow-ups for at least 36 months were studied. Age, gender, performed surgical procedure, pathology results, recurrence, distant and lymph node (LN) metastasis, mortality, and follow-up period, tumour histological type, microscopic variant, tumor diameter, bilaterality, focality, tumor localization, presence of capsule of the tumor, capsule invasion in the tumor, parenchymal, lymphatic, perineural, and vascular invasion, necrosis, mitosis, calcification, surgical borders were studied.

Results: The mean tumour size was 5 mm (0.1-10 mm), and multifocality was seen in 137 (53.7%) patients. Capsule invasion was observed in 23 (9%) patients. Vascular invasion was present in 5 (2%) patients, the lymphatic invasion was present in 14 (5.5%) patients, and extrathyroidal invasion was present in 2 (0.8%) patients. Metastatic cervical LN were present in 24 (9.4%) patients. Comparing patients with and without LN metastasis in terms of pathology results, it was observed that lymphatic invasion and calcification presented by the tall cell variant were significantly higher in patients with LN metastasis. In addition, tumor size was larger in those with LN metastasis. Tumor size (P=0.004; OR=1.380; 95% CI=1.106-1.722) and gender (P=0.013; OR:4.233; 95% CI=1.355-13.226) were found to be the main predictive factors affecting LN metastasis, as a result of the regression analysis. It was observed that LN metastasis were more common in males than females and seen more frequently as the tumour size increased.

Conclusion: Male gender and large tumour size (cut-off 6.75 mm) were found to be the factors associated with LN metastasis. It is recommended that these factors should be considered in the treatment decision, especially in LN-negative patients, regarding prophylactic central compartment neck dissection. In case of the distant metastasis without regional LN metastasis, further studies on molecular markers are needed.