The presence of the medullary thyroid carcinoma (MTC) subtype might negatively affect the prognosis of patients with thyroid collision tumors (TCTs), according to an article published in Diagnostics

“Regarding the high-risk histopathological features, only mETE due to TCTs’ MTC component proved to be statistically different compared to MTC-only tumors, pointing out that TCTs’ MTC component may be more aggressive than MTC-only tumors,” the authors wrote.

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This comparative, retrospective, observational study included a total of 35 cases of TCTs, of which the majority (n=23) had an MTC and a papillary thyroid carcinoma (PTC) component. The authors compared these cases with another 23 patients who had only MTC tumors and 23 patients with only PTC tumors. All individuals with either pure MTC or PTC had an equal pathological T category of those from the TCTs components. 

As expected, the prominent TCT component showcased lymph node metastasis, lymphovascular invasion, perineural invasion, and microscopic extrathyroidal extension at a higher rate than the other component. Noticeably, the MTC component exhibited lymphovascular invasion more frequently. 

Interestingly, only the MTC component of TCTs was significantly more associated with microscopic extrathyroidal extension when compared to pure MTC tumors. Moreover, the new MTC grading system’s pathological parameters of the MTC component of TCTs did not display any correlation with additional clinical or microscopic features. 

Collision tumors are defined as 2 or more morphologically different tumors that develop synchronously in the same organ but with normal tissue between the tumors. In this study, as well as in other publications, most (52.17%) cases had both components located in the same lobe, suggesting a hypothesis that an initial tumor sets an environment that promotes the development of the second tumor. Although a rare entity, the results of this article provides valuable information for the understanding and treatment of TCTs. 

“Additionally, the increased incidence of tumor LVI in TCTs with an MTC component requires neck dissection with lymphadenectomy in the central and lateral compartment for staging and locoregional tumor control,” the authors explained. 


Negura I, Ianole V, Danciu M, et al. Thyroid collision tumors: the presence of the medullary thyroid carcinoma component negatively influences the prognosis. Diagnostics. Published online January 12, 2023. doi:10.3390/diagnostics13020285