Primary anorectal mammary-like adenocarcinoma: a potential diagnostic pitfall with conventional colorectal adenocarcinoma.

Anogenital mammary-like glands (AGMLGs) are present in the anogenital region that bear striking morphologic and protein-expression similarities to mammary glands in the breast. AGMLGs can give rise to both benign and malignant lesions which mimic primary breast lesions. Herein, we report two mammary-type adenocarcinomas arising from AGMLGs, including one in the previously unreported site of the rectum. Recognition of mammary-type adenocarcinoma in the rectal and anogenital regions is crucial as clinical management options may differ compared to conventional colorectal adenocarcinomas.