A Case of Medullary Thyroid Carcinoma Combined with Papillary Microcarcinoma and Literature Review

Background: The histologic type of thyroid carcinomas includes follicular, papillary carcinomas, and medullary carcinomas. The reports about the histological, immunohistochemical, and ultrastructural characteristics of each kind of thyroid carcinomas were common, but the simultaneous occurrence of a medullary and papillary carcinoma as 2 distinct tumors has been reported extremely rarely. Objects: To explore the pathogenesis, clinicopathological characteristics, immunohistochemical phenotype, and pathological diagnosis of medullary thyroid carcinoma combined with papillary thyroid microcarcinoma. Methods: The clinicopathological characteristics and immunohistochemical phenotype of a patient with left medullary thyroid carcinoma combined with right papillary thyroid microcarcinoma were retrospectively studied. Then, relevant literature was thus reviewed. Results: General appearance: The size of the left thyroid lobe was 2.5 × 2 × 1 cm, the cut surface was gray and red, and a nodule with a diameter of 1.3 cm could be observed. The cut surface of the nodule was gray and yellow, solid, and hard. The size of the right lobe of the thyroid gland was 0.7 × 0.6 × 0.5 cm, and a gray nodule with a diameter of 0.4 cm was seen on the cut surface. The cut surface of the nodule was gray, solid, and hard. Observation under the microscope: the left nodular tumor cells were round, oval, or plasma cell-like, some areas were arranged in nests, and some areas were arranged in beams. Calcification and sheet-like eosinophilic amyloid deposits could be seen in the stroma. The nodule on the right showed a branched papillary structure, the covering cells on the surface of the nipple were ground glass-like nuclei, and nuclear grooves and pseudo-inclusion bodies in the nucleus could be observed. Immunohistochemistry: left lobe tumor cells Calcitonin, CEA, TTF-1, CD56, CgA, and Syn are all (+), CK19 and TG were both (−); right lobe tumor cells CK19 and TG are both (+), Calcitonin, CD56, CgA, and Syn are all (−). Conclusions: The origin, clinicopathological manifestations, and immunophenotypes of medullary thyroid carcinoma and papillary thyroid carcinoma are different. It is relatively rare for the two to occur at the same time. The diagnosis mainly depends on the microscopic morphology and immunophenotype characteristics.