breast cancer; covid 19; VACCINATION FAILURE; her left arm (Vaccinated arm) hurt; This spontaneous case was reported by a patient and describes the occurrence of BREAST CANCER (breast cancer) in a 59-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 041L20A) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.     The patient was healthy. The patient did not receive any other vaccines in the 4 months prior to COVID-19 vaccine.    On 09-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 06-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In 2021, the patient experienced VACCINATION SITE PAIN (her left arm (Vaccinated arm) hurt). On 07-Aug-2021,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced COVID-19 (covid 19) and VACCINATION FAILURE (VACCINATION FAILURE). On 11-Jul-2023, the patient experienced BREAST CANCER (breast cancer) (seriousness criterion medically significant). The patient was treated with Surgery (double mastectomy on 13SEP2023) for Breast cancer. At the time of the report, BREAST CANCER (breast cancer) and COVID-19 (covid 19) had not resolved and VACCINATION SITE PAIN (her left arm (Vaccinated arm) hurt) and VACCINATION FAILURE (VACCINATION FAILURE) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In May 2021, Mammogram: The lymph node was Enlarged.. On 07-Aug-2021, SARS-CoV-2 test: Positive. In December 2021, Ultrasound scan: enlarged lymph nodes on the left side. In 2022, Ultrasound scan: 2 lymph nodes enlarged on the left side. In July 2023, Biopsy: invasive ductal Carcinoma with score 6/9 Left breast Tumor Size Biopsy: 8MM Stage 1 Cancer , Grade 2 in Left Breast..     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   No concomitant medication was reported.  The patient was not on any medications at the time receiving Moderna COVID-19 vaccine. But the patient's Dad and 2 uncles (half brothers) had Colon Cancer. The patient never had an abnormal Mammogram prior to vaccination. It was always normal. The patient was prescribed pain Medications post Mastectomy. The patient did not want to take a chance and removed both breasts (No cancer in right breast). The patient states that in addition to taking the tumor out, the doctors took 2 lymph nodes out of the left breast but those were benign.  Company comment- This spontaneous case concerns a 59-year-old female patient with no medical history reported, who experienced the unexpected and serious (medically significant) event breast cancer approximately 2 years and 6 months after a second dose of mRNA-1273 vaccine was administered. Patient tested positive for COVID-19 test and a non-serious unexpected event of COVID-19 was also reported after a primary series of two doses of mRNA-1273 vaccine administered in an appropriate schedule of vaccination (28 days interval, vaccination failure). Three months after second vaccine was given patient had her annual mammogram. They told her that her lymph node was enlarged. 6 Months later, she followed up with a sonogram which revealed enlarged lymph nodes on the left side. One year later, they found 2 lymph nodes enlarged on the left side. Finally, she was diagnosed with breast cancer (invasive ductal carcinoma with score 6/9 left breast tumor Stage 1 Cancer, Grade 2 in left breast) and had double mastectomy.  She was healthy, she never had an abnormal mammogram prior to vaccination. The event breast cancer was assessed as not related to mRNA-1273 vaccine due to lack of biological plausibility. The benefit risk relationship of mRNA-1273 vaccine is not affected by this report.