Abstract
RATIONALE: Synchronous double primary cancer refers to 2 independent primary tumors that occur in the same organ at the same time or within 6 months. We report a case of double primary carcinoma of thyroid gland with different histological subtypes, which is composed of papillary thyroid carcinoma and medullary thyroid carcinoma. Usually, thyroid carcinoma will be confirmed by intraoperative freezing, but it is very easy to miss the diagnosis because of the minimal atypia of medullary carcinoma. This paper introduces a detailed case, aiming to understand the significance of laboratory examination and imaging examination for a clear diagnosis in this case. PATIENT CONCERNS: Here, we report a 61-year-old female patient who was found with multiple thyroid nodules by physical examination a month ago. The results of preoperative laboratory examination and puncture biopsy suggested that medullary thyroid carcinoma was possible, but the results of imaging examination and intraoperative frozen section suggested that papillary thyroid carcinoma was possible. In the last routine paraffin section, it was confirmed that it was a case of double primary thyroid carcinoma. DIAGNOSES: Paraffin sections of surgical specimens were finally diagnosed as synchronous double primary cancers with different histological subtypes of thyroid. INTERVENTIONS: After the operation, the left thyroid gland was fully taken and made, and the final diagnosis was made clear. OUTCOMES: The patient has successfully undergone surgery, and the serum calcitonin levels have returned to normal. LESSONS: This rare situation emphasizes the support of imaging examination and laboratory examination for final diagnosis and the limitation of frozen section.