The clinical and pathological characteristics of 30 patients with synchronous medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma have been described in a recently published study in Frontiers.

MTC and PTC have different histological origins and markedly different clinical features and prognoses, the former being associated with increased calcitonin prognosis and a higher rate of mortality, the researchers noted.

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PTC is, with a difference, the most common type of thyroid carcinoma, accounting for more than 90% of cases. Its simultaneous occurrence with other thyroid carcinomas, such as MTC, is rare and accounts for less than 1% of cases.

“We retrospectively studied the clinical profiles and pathological features of 30 combined PTC and MTC diagnosed over a 14-year period,” the authors wrote.

Synchronous tumors were classified into 4 different subtypes, namely type 1 referring to closely intermingled tumors. Type 2 is represented by tumors that invade each other, appearing like a single mass, type 3 is a form in which tumors are separated from each other by normal thyroid tissue in the same lobe; and type 4, with different tumors in different lobes.

Data were extracted from the database of the China-Japan Union Hospital in Jilin, China, which performs over 4000 thyroid surgeries a year. Among more than 2800 thyroid tumors operated on during a 14 year period, 30 were diagnosed as synchronous MTC and PTC, representing an incidence below 0.1%.

Type 3 tumors were the most common in the studied sample, accounting for 14 cases, followed by type 4 in 10 cases and type 1 and 2 in 4 and 2 cases, respectively. Lymph node metastases occurred in 1 case, whilst infiltration of extrathyroidal tissue occurred in 10. MTC was the dominant tumor in 15 cases and PTC in 14.

The mean duration of symptoms among the 30 patients was between 11 and 18 months, with thyroid swelling being the most prevalent, followed by dysphagia. Thyroid function tests were between normal limits in all patients.

Of the 21 tumors examined through fine needle aspiration before surgery, 2 were initially classified as MTC, 1 as MTC, and 18 as either PTC of unspecified thyroid carcinoma.

In the follow-up period, 2 patients died due to liver metastases, and local recurrences occurred in 4 patients. In all 4 patients, calcitonin levels were higher than usual, and in 3 cases, carcinoembryonic antigen levels were over normal limits.

“This is probably the most numerous case series reported in the literature. Unique clinical and pathological aspects and outcomes are presented,” the authors wrote.


Zhang D, Yang M, Zhang X, et al. Thirty synchronous medullary and papillary thyroid carcinomas. Front Endocrinol. Published online March 31, 2023. doi:10.3389/fendo.2023.1153248