[The pathological characteristics and prognostic analysis of medullary thyroid microcarcinoma]

Objectives: To analyze the clinical characteristics and prognosis of medullary thyroid microcarcinoma (MTMC). Methods: A case series studies. The clinical data of patients with medullary thyroid carcinoma (MTC) diagnosed by postoperative pathology and with complete follow-up data who were initially treated in Tianjin Medical University Cancer Hospital from January 2013 to December 2019 were retrospectively analyzed. There were a total of 170 cases, including 70 males and 100 females, aged (49.7±12.3) years old. Among them, there were 61 patients with MTMC. They were divided into group A (with a maximum tumor idameter of ≤0.5 cm, n=13) and group B (with a maximum tumor diameter >0.5~≤1.0 cm, n=48) based on whether the maximum diameter of the tumor was >0.5 cm. Analysis was conducted on their pathological results and prognosis. Results: Among the MTC, MTMC accounted for 26.4% (61/231) with 26 males and 35 females aged M［Q₁，Q₃］51.0 (41.0, 59.0) years. Among the MTMC patients, 57.4% (35/61) were in stage Ⅰ, 16.4% (10/61) were in stage Ⅲ, and 26.2% (16/61) were in stage Ⅳ. For MTMC with a maximum diameter of≤0.5 cm and a maximum diameter of >0.5-≤1.0 cm, there was no statistically significant difference between the two groups in terms of gender, age, mixed cancer, invasion of glandular lobes, multifocal, central lymph node metastasis, lateral neck lymph node metastasis rate and other pathological characteristics(both P>0.05). In terms of prognosis, the recurrence free survival time of MTMC patients was 83.1 (68.0, 97.0) months. Among them, structural tumor recurrence occurred in 5 patients (8.2%) after surgery, and 1 patient (1.6%) died. The expected 5-year and 10-year survival rates were 93.4% and 89.0%, respectively. There was no statistically significant difference in recurrence free survival time among MTMC patients, MTC patients with a maximum diameter of >1.0-≤2.0 cm, and MTC patients with a maximum diameter of >2.0 cm (all P>0.05). Conclusion: MTMC has strong invasiveness, and although the prognosis of most MTMCs is relatively good, the risk of long-term recurrence and death is still high.