A patient with Peutz-Jeghers syndrome, a sex cord tumor with annular tubules, and an initially unrecognized adenoma malignum of the cervix is described. The patient presented with a mucinous adenocarcinoma in the vaginal apex. Review of the hysterectomy slides demonstrated an adenoma malignum of the cervix. In addition to a microscopic sex cord tumor with annular tubules of the right ovary, the left ovary contained mucinous cystadenomas. Adenoma malignum remains a difficult diagnosis and is frequently made only after hysterectomy for a presumed benign indication; pathology frequently demonstrates a deeply invasive, unusually well-differentiated adenocarcinoma of the cervix. Patients with Peutz-Jeghers syndrome need careful clinical and cytologic follow-up to exclude such lesions.