Multifocality, but not bilaterality, is a predictor of disease recurrence/persistence of papillary thyroid carcinoma

Although papillary thyroid carcinoma (PTC) often presents as multifocal or bilateral tumors, but whether multifocality or bilaterality is associated with disease recurrence/persistence is controversial. We evaluated the association between multifocality and bilaterality of PTC and disease recurrence/persistence. We also analyzed the location and number of tumors in multifocal PTC.

We reviewed the medical records of 2,095 patients who underwent total thyroidectomy for PTC. Tumors were classified as solitary or multifocal PTC according to the number of tumors present. Multifocal PTCs were subdivided into multifocal-unilateral and multifocal-bilateral PTC based on the tumor location. Solitary tumor or multifocal tumors located in one lobe were classified as unilateral PTC, and tumors in both lobes were classified as bilateral PTC. We analyzed the clinicopathologic features and clinical outcomes in each classification. Logistic regression models were used to assess the relation between multifocality or bilaterality and disease recurrence/persistence.

Extrathyroidal invasion, cervical lymph node metastasis, and advanced TNM stage were significantly more frequent in multifocal PTC than in solitary PTC. Extrathyroidal invasion, cervical lymph node metastasis, advanced TNM stage, and distant metastasis were significantly more frequent in bilateral PTC than in unilateral PTC. The clinicopathologic parameters did not differ significantly between patients with multifocal-unilateral and multifocal-bilateral PTC. Multifocality was found to be an independent predictor of disease recurrence/persistence [odds ratio (OR) 1.45, 95 % confidence interval (CI) 1.01-2.10, p = 0.04]. However, there was no association between bilaterality and disease recurrence/persistence (OR 0.98, 95 % CI 0.64-1.48, p = 0.92). In multifocal PTC, the number of tumors (OR 1.75, 95 % CI 1.04-2.97, p = 0.04), but not the location of tumors (OR 0.56, 95 % CI 0.31-1.02, p = 0.06), was significantly associated with disease recurrence/persistence.

Although multifocal and bilateral PTC had aggressive pathologic features, only multifocality was associated with an increased risk of disease recurrence/persistence. This suggests that the number of tumor foci, but not their location, is a significant predictor of clinical outcomes.