Mucosa-associated lymphoid tissue lymphoma flare; Ulcerative colitis flare; This literature-non-study case was reported in a literature article and describes the occurrence of EXTRANODAL MARGINAL ZONE B-CELL LYMPHOMA (MALT TYPE) (Mucosa-associated lymphoid tissue lymphoma flare) and COLITIS ULCERATIVE (Ulcerative colitis flare) in a 56-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis.       Concurrent medical conditions included Left-sided ulcerative (chronic) colitis since 1993. Concomitant products included OLSALAZINE, PREDNISONE and MESALAMINE for an unknown indication.    On an unknown date, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced EXTRANODAL MARGINAL ZONE B-CELL LYMPHOMA (MALT TYPE) (Mucosa-associated lymphoid tissue lymphoma flare) (seriousness criterion medically significant) and COLITIS ULCERATIVE (Ulcerative colitis flare) (seriousness criterion medically significant). At the time of the report, EXTRANODAL MARGINAL ZONE B-CELL LYMPHOMA (MALT TYPE) (Mucosa-associated lymphoid tissue lymphoma flare) and COLITIS ULCERATIVE (Ulcerative colitis flare) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Biopsy colon: revealed chronic nonspecific colitis. On an unknown date, Colonoscopy: revealed two 7 mm sessile, non-bleeding rectal polyps, surrounded by congested, erythematous, friable, and ulcerated mucosa in the rectosigmoid colon. On an unknown date, Immunohistochemistry: confirmed extra-nodal marginal zone lymphoma of MALT with prominent plasmacytic differentiation. On an unknown date, Pathology test: showed marked lymphoplasmacytic infiltrate and extranodal marginal zone lymphoma of MALT.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   No concomitant medication was reported.  Patient was asymptomatic, found to have benign appearing rectal polyps during a routine screening colonoscopy. The patient had regular non-bloody bowel movements and normal stool consistency. Ancillary studies, immunohistochemistry, and molecular studies for B-cell gene rearrangement confirmed extra-nodal marginal zone lymphoma of MALT with prominent plasmacytic differentiation.  Company Comment: This is a Literature non-study case concerning a 56-year-old female patient, with underlying left-sided ulcerative colitis, who experienced the unexpected and serious (due to medically significant) events of Extranodal marginal zone B-cell lymphoma (MALT type) and Ulcerative colitis, which occurred on an unknown date after mRNA-1273 vaccine, administered as second dose within COVID-19 vaccination schedule. As reported, patient experienced one flare after the second dose. She was taking oral Olsalazine 500 mg twice daily, low-dose Prednisone, and mesalamine suppositories as needed. The patient was asymptomatic, citing regular non-bloody bowel movements and normal stool consistency. She presented to a screening colonoscopy, which revealed two 7 mm sessile, non-bleeding rectal polyps, surrounded by congested, erythematous, friable, and ulcerated mucosa in the rectosigmoid colon. Cold forceps biopsies were taken. Hematopathology evaluation of the routine colon biopsy samples revealed chronic nonspecific colitis while pathology of the rectal polyps showed marked lymphoplasmacytic infiltrate and extranodal marginal zone lymphoma of MALT. Ancillary studies, immunohistochemistry, and molecular studies for B-cell gene rearrangement confirmed extra nodal marginal zone lymphoma of MALT with prominent plasmacytic differentiation. At the time of the report, outcome was unknown. Underlying ulcerative colitis can present relapses as part of natural history of the disease, confounding the case. The benefit-risk relationship of mRNA-1273 vaccine.; Sender's Comments: Company Comment: This is a Literature non-study case concerning a 56-year-old female patient, with underlying left-sided ulcerative colitis, who experienced the unexpected and serious (due to medically significant) events of Extranodal marginal zone B-cell lymphoma (MALT type) and Ulcerative colitis, which occurred on an unknown date after mRNA-1273 vaccine, administered as second dose within COVID-19 vaccination schedule. As reported, patient experienced one flare after the second dose. She was taking oral Olsalazine 500 mg twice daily, low-dose Prednisone, and mesalamine suppositories as needed. The patient was asymptomatic, citing regular non-bloody bowel movements and normal stool consistency. She presented to a screening colonoscopy, which revealed two 7 mm sessile, non-bleeding rectal polyps, surrounded by congested, erythematous, friable, and ulcerated mucosa in the rectosigmoid colon. Cold forceps biopsies were taken. Hematopathology evaluation of the routine colon biopsy samples revealed chronic nonspecific colitis while pathology of the rectal polyps showed marked lymphoplasmacytic infiltrate and extranodal marginal zone lymphoma of MALT. Ancillary studies, immunohistochemistry, and molecular studies for B-cell gene rearrangement confirmed extra nodal marginal zone lymphoma of MALT with prominent plasmacytic differentiation. At the time of the report, outcome was unknown. Underlying ulcerative colitis can present relapses as part of natural history of the disease, confounding the case. The benefit-risk relationship of mRNA-1273 vaccine.