Metastatic breast carcinoma; Axillary lymphadenopathy; This literature-non-study case was reported in a literature article and describes the occurrence of BREAST CANCER METASTATIC (Metastatic breast carcinoma) in a 60-year-old female patient who received mRNA-1273 (Spikevax) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.       No Medical History information was reported.    On an unknown date, the patient received dose of mRNA-1273 (Spikevax) (unknown route) 1 dosage form. On an unknown date, the patient experienced BREAST CANCER METASTATIC (Metastatic breast carcinoma) (seriousness criterion medically significant) and LYMPHADENOPATHY (Axillary lymphadenopathy). At the time of the report, BREAST CANCER METASTATIC (Metastatic breast carcinoma) and LYMPHADENOPATHY (Axillary lymphadenopathy) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Biopsy: diagnosed with metastatic breast carcinoma. On an unknown date, Pathology test: diagnosed with carcinoma and adenocarcinoma.     The action taken with mRNA-1273 (Spikevax) (Unknown) was unknown.   For mRNA-1273 (Spikevax) (Unknown), the reporter did not provide any causality assessments.   No concomitant and treatment medications were reported.  Patient presented with left axillary lymphadenopathy (enlarged lymph node) and concurrent suspicious breast findings (irregular mass in the breast) 9 weeks following COVID-19 vaccination.  Company comment:This literature-non-study case concerns a 60-year-old, female patient with no information about medical history provided, who experienced the unexpected serious (medically significant) event of breast cancer metastatic and non serious event of Axillary lymphadenopathy. The events occurred approximately 9 weeks after a dose of mRNA-1273. No information about dose number or vaccination schedule was provided. As reported, patient presented with left axillary lymphadenopathy (enlarged lymph node) and concurrent suspicious breast findings (irregular mass in the breast) 9 weeks following COVID-19 vaccination and was ultimately diagnosed with biopsy proven metastatic breast carcinoma. Causality for the event of metastatic breast cancer was assessed as not related considering the nature of the event and advanced stage(metastasis) found 9 weeks following vaccination. Event of axillary lymphadenopathy is confounded by concurrent breast carcinoma. The benefit-risk relationship of mRNA-1273 is not affected by this report.   This case was linked to US-MODERNATX, INC.-MOD-2022-661135.; Sender's Comments: This literature-non-study case concerns a 60-year-old, female patient with no information about medical history provided, who experienced the unexpected serious (medically significant) event of breast cancer metastatic and non serious event of Axillary lymphadenopathy. The events occurred approximately 9 weeks after a dose of mRNA-1273. No information about dose number or vaccination schedule was provided. As reported, patient presented with left axillary lymphadenopathy (enlarged lymph node) and concurrent suspicious breast findings (irregular mass in the breast) 9 weeks following COVID-19 vaccination and was ultimately diagnosed with biopsy proven metastatic breast carcinoma. Causality for the event of metastatic breast cancer was assessed as not related considering the nature of the event and advanced stage(metastasis) found 9 weeks following vaccination. Event of axillary lymphadenopathy is confounded by concurrent breast carcinoma. The benefit-risk relationship of mRNA-1273 is not affected by this report. US-MODERNATX, INC.-MOD-2022-661135:50-YO Female