Thirty synchronous medullary and papillary thyroid carcinomas

Synopsis for table of contents: An exceptional number of synchronous MTC/PTC in the same thyroid gland is presented. This may be the most numerous case series reported in the literature. Synchronous PTC/MTC in the same thyroid gland were classified into 4 subtypes and the clinical and pathological aspects as well as the results are presented.

Background and objectives: The synchronous occurrence of multiple neoplastic processes in the thyroid gland is unusual. We investigated the clinicopathological features of 30 medullary thyroid carcinomas (MTC) in association with papillary (PTC).

Method: Retrospective analysis of operated patients for thyroid tumors. Synchronous PTC/MTC in the same thyroid gland were classified into 4 subtypes: (type I) True mixed MTC/PTC, MTC and PTC closely intermingled. (Type II) Collision MTC/PTC, i.e. tumors that meet at the same site, invade each other and appear as a single mass in the thyroid gland, i.e. MTC and PTC merge. (Type III) Synchronous anatomically separate tumors in the same thyroid lobe, i.e. separated from each other by non-tumorous thyroid parenchyma. (Type IV) Synchronous tumors occurring in separate anatomical lobes or in the isthmus. Clinical and pathological data were reviewed. Location: Department of thyroid surgery, China-Japan Union Hospital, Jilin University. Time frame: 14 years (June 2008-November 2022).

Results: Thirty patients were identified with an overall prevalence of 28621 (0.1%). 17 (56.7%) were male, 13 (43.3%) female, mean age 51.3 ± 11.0 years, mean BMI 23.6 ± 3.6kg/m2. Mean duration of symptoms was 11.2 ± 18.4 months. Mean calcitonin level was 133.7 ± 196.4 pg/ml. Fine needle aspiration (FNA) was offered in 21 cases: 9 (42.9%) were suspected carcinoma, 9 (42.9%) PTC, 1 (4.8%) MTC, 2 (9.4%) MTC/PTC. Pathology revealed type I 4 (13.3%), type II 2 (6.7%), type III 14 (46.7%), type IV 10 (33.3%). The mean diameter of MTC was 1.6 ± 2.0cm, 18 (60%) were micro-MTC. The mean diameter of PTC was 0.9 ± 1.9 cm, 26 (86.7%) were micro-PTC. In 16 (53.3%) micro-PTC/-MTC occurred in synchronous sequence. Four patients had a recurrence: 2 had to be re-operated due to MTC recurrence, 2 died due to distant metastases (bone, liver).

Conclusion: We report an exceptional number of MTC/PTC in the same thyroid gland. This may be the most numerous case series reported in the literature. The clinical and pathological aspects as well as the results are presented.