An Uncommon Culprit: Cytomegalovirus Colitis Mimicking Malignancy in an Immunocompetent Patient.

Cytomegalovirus (CMV) can cause ulcerative lesions in the gastrointestinal tract, but it does not typically cause severe infections in immunocompetent patients. CMV colitis presenting as a rectal mass is a very rare manifestation often mimicking malignancy. This is an 89-year-old Caucasian female patient with a circumferential ulcerating mass and a sigmoid polyp that was found to be positive for CMV in the immunohistochemical staining. This is a rare presentation of CMV colitis, especially in an immunocompetent patient. The rarity of this disease presentation exemplifies the importance of a thorough workup for diagnosis.