Malignant lesions of the female genital tract and peritoneum that may be underdiagnosed.

Female genital tract neoplasms that may have a deceptively benign appearance and selected frankly malignant neoplasms that may be misinterpreted as less aggressive lesions are reviewed. In the uterine cervix, the two major neoplasms in this group are the minimal deviation adenocarcinomas of mucinous and endometrioid types. The latter subtype has only recently been described. Endometrioid adenocarcinomas, usually of the uterine corpus, but occasionally of other sites, may have microglandular patterns that can lead to their misdiagnosis, sometimes as microglandular hyperplasia. Pure squamous cell carcinomas of the uterine corpus frequently are composed of very well differentiated epithelium, so that it is possible to misinterpret them as nonneoplastic, and a similar phenomenon may occur in association with the squamous element in some adenocarcinomas with squamous differentiation. Other uterine entities that may be underdiagnosed are malignant lymphoma of the cervix, placental site trophoblastic tumor, myxoid leiomyosarcoma, endometrial stromal sarcoma with glandular differentiation, and mullerian adenosarcoma. Consideration of a variety of architectural and cytological features should facilitate their interpretation. One recently described variant of adenocarcinoma of the fallopian tube that may be confused with the usually clinically benign female adnexal tumors of probable Wolffian origin is microfollicular endometrioid adenocarcinoma. Ovarian tumors subject to misinterpretation that are reviewed herein include metastatic tumors with deceptively benign foci, endometrioid adenocarcinomas that may be misdiagnosed as sex cord tumors, and cystic granulosa cell tumors that may be misinterpreted as follicle cysts. Finally, rare variants of malignant mesothelioma that may be underdiagnosed are reviewed.