Which papillary thyroid microcarcinoma should be treated as "true cancer" and which as "precancer"?

Papillary thyroid microcarcinoma (PTMC) generally is a cancer with excellent prognosis, but the term "cancer" sounds severe and harsh, which can elicit emotional and physical responses from patients. To eliminate the word "cancer," the term noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was introduced. However, not all PTMCs can be classified as NIFTP. Sometimes, very aggressive PTMC cases might be observed. Some authors suggest that one of the risk factors for poor prognosis is lymph node metastasis. The aim of the study was to evaluate some clinicopathological features of PTMC as the risk factors for lymph node metastasis.

We performed a retrospective chart review and selected 177 patients with PTMC. To analyze the cases with potentially aggressive behavior, we enrolled PTMC patients with lymph node metastases (pN1, central, and/or lateral) and evaluated some of their clinicopathological features.

The logistic regression analysis results demonstrated significantly higher rates of multifocal or bilateral tumor occurrence in the PTMC patients with pN1 than in the patients with pN0 (P < 0.0001 for both). In addition, the occurrence of thyroid tumors with sizes above 0.5 cm was a significant risk factor for lymph node metastasis (P < 0.0001). The results of the ROC analyses showed that the presence of multifocal or bilateral tumors and tumor sizes above 0.5 cm were significant predictors of lymph node metastasis (P < 0.0001 for all).

Multifocal and bilateral PTMC tumors with diameters above 0.5 cm should be treated aggressively as "true cancer" and might benefit from lymph node dissection. Unifocal PTMC tumors with diameters equal to or below 0.5 cm may be treated less aggressively.