A tertiary-center experience of patients with simultaneous medullary and papillary thyroid carcinomas

Papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma (MTC) are thyroid carcinomas of different embryological origin. Over the past few decades, several cases have been reported in which PTC and MTC coexist in the same lymph node but separated by normal tissue, this being termed mixed medullary/follicular thyroid carcinoma (MMFTC). Our study aimed to investigate the prevalence of PTC in a cohort of MTC patients in an attempt to define (a) the clinical phenotype of patients with MTC/PTC and (b) any potent association with age, carcinoembryonic antigen (CEA), calcitonin levels, gender or number of operations.

This is a single-center retrospective observational study of an endocrinology outpatient clinic at a tertiary general university hospital. All patients diagnosed with MTC/PTC between November 2017 and March 2021 were recruited. Those with positive RET were excluded. Statistical analysis was performed using SPSS software (SPSS 25. Inc. Chicago, IL).

A total of 30 patients with MTC/PTC, either as separate tumors or as collision tumors combining MTC and PTC, were included in our study. The mean age was 58.43 ± 12.31 years. Slightly over half of the patients were males (53.3%). Univariate analysis showed no association between MTC/PTC, either as separate tumors or as collision tumors, coexistence and age, calcitonin levels, CEA, gender, number of metastases, or number of operations. Multivariate analysis confirmed no significant associations, although the small sample size limited its scope.

In our small case series, no association was demonstrated between simultaneous MTC/PTC and age, CEA, calcitonin levels, gender, or number of operations. This entity likely represents a primary tumor with an incidental pathologic finding of a second malignancy.