Diagnosed with thyroid cancer; This spontaneous case was reported by a consumer and describes the occurrence of THYROID CANCER (Diagnosed with thyroid cancer) in a 36-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 0/O 29A21A and 019B21A) for COVID-19 vaccination.     No Medical History information was reported.   On 03-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 31-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In March 2021, the patient experienced THYROID CANCER (Diagnosed with thyroid cancer) (seriousness criterion medically significant). The patient was treated with Surgery (Removed thyroid and Radiotherapy with radioactive iodine) for Thyroid cancer. At the time of the report, THYROID CANCER (Diagnosed with thyroid cancer) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In March 2021, Biopsy: abnormal (abnormal) Thyroid cancer.     mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) and mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosing remained unchanged.       No concomitant was provided. After the first dose patient  was referred to a endocrinologist who did a biopsy. patient  was diagnosed with thyroid cancer. On 20 April 2021 they removed the thyroid and on 09 Sept 2021 was given radioactive iodine that killed the rest of the thyroid gland . Patient states because they could not remove the entire thyroid.  Patient clarified the diagnosis came after dose 1 and before dose 2.  Company comment: This spontaneous report concerns a 36 year old male patient with no relevant medical history who experienced a serious unexpected event of thyroid cancer. The event occurred one day after vaccination with first dose of mRNA-1273. The patient reports having noticed a red marble sized spot on left side of his neck which increased in size within a week. Upon biopsy of the lesion, the patient was diagnosed with thyroid cancer. Thyroid removal surgery was performed 20 days after the patient was vaccinated with second dose of mRNA-1273. Five months post surgery, the patient was treated with radioactive iodine therapy for removal of the residual thyroid tissue. The outcome of the event was unknown. The benefit-risk relationship of mRNA-1273 is not affected by this report.; Sender's Comments: This spontaneous report concerns a 36 year old male patient with no relevant medical history who experienced a serious unexpected event of thyroid cancer. The event occurred one day after vaccination with first dose of mRNA-1273. The patient reports having noticed a red marble sized spot on left side of his neck which increased in size within a week. Upon biopsy of the lesion, the patient was diagnosed with thyroid cancer. Thyroid removal surgery was performed 20 days after the patient was vaccinated with second dose of mRNA-1273. Five months post surgery, the patient was treated with radioactive iodine therapy for removal of the residual thyroid tissue. The outcome of the event was unknown. The benefit-risk relationship of mRNA-1273 is not affected by this report.