A patient with a long-standing intrauterine contraceptive device (IUCD) develops chronic pelvic pain. The device is removed, and a biopsy of the endometrium is performed. The biopsy specimen shows a prominent infiltrate composed of lymphocytes, plasma cells, and histiocytes. Which of the following is the most likely diagnosis?

This is chronic endometritis, evidenced by the chronic inflammatory infiltrate of lymphocytes, plasma cells, and histiocytes. This disorder may be idiopathic but is more often associated with an obvious predisposing factor, such as chronic pelvic inflammatory disease, tuberculosis, retained gestational tissue, or as in this case, an intrauterine contraceptive device. Chronic endometritis can cause abnormal bleeding, pain, and infeility. Acute endometritis is characterized by a prominent neutrophilic infiltrate and usually occurs after delivery or miscarriage. Adenomyosis refers to endometrium abnormally located in myometrium. Endometriosis refers to abnormally located patches of endometrium (except in the myometrium, where it would be called adenomyosis).