Multi- and Unifocal Thyroid Microcarcinoma: Are There Any Differences?

BACKGROUND: Thyroid microcarcinoma (TMC) often occurs as two or more separate foci, therefore a completion of primary surgery might be necessary.

OBJECTIVES: To evaluate and compare the incidence, diagnostic accuracy, clinicopathological characteristics and surgical treatment of unifocal and multifocal thyroid microcarcinoma (UTMC vs. MTMC).

MATERIAL AND METHODS: We retrospectively analyzed 3,218 medical records of patients consecutively admitted and surgically treated in one center due to thyroid pathology.

RESULTS: In the end, we evaluated 246 (7.64%) patients with thyroid malignancy. Ninety-seven of them (39.43%) were diagnosed as TMC: 84 (86.59%) UTMC and 13 (13.41%) MTMC (p < 0.0001). All MTMC were unilateral tumors. The papillary type of cancer was found in 82 (97.62%) patients with UTMC and in 12 (92.31%) with MTMC (p = 0.8661). In the UTMC group, 1 (1.19%) patient had follicular and 1 (1.19%) the medullary type of TMC. 1 (7.69%) individual in the MTMC group had tumors composed of papillary and follicular cancer. The number of younger patients (age < 45) was comparable in both groups (p = 0.825). The trend was observed that ultrasound guided fine needle aspiration biopsy (UG-FNAB) revealed malignant processes before surgery in a greater number of patients with MTMC than UTMC (84.62% vs. 58.33%, p = 0.131). In the MTMC group, the number of larger tumors (> 5 mm) was greater (84.62% vs. 65.48%), however the difference was not statistically significant. Thirteen percent of patients with UTMC presented cervical lymph node involvement, compared to nearly 8% of patients with MTMC (p = 0.298). Disease-related mortality was not observed in either group.

CONCLUSIONS: The prevalence of UTMC was significantly higher than MTMC. The majority of UTMC and MTMC were composed of the papillary type of cancer. MTMC and UTMC were equally frequent in both age groups. The accuracy of UG-FNAB was higher in patients with MTMC. The dimensions of most UTMC and MTMC was above 5 mm. The involvement of the cervical lymph node at the time of diagnosis in both groups is comparable and not infrequent.