Endometriosis is defined as the presence of endometrial tissue outside the uterus. The most common sites affected are the ovaries, uterine ligaments, recto- and vesico-vaginal septae, pelvic peritoneum, cervix, labia and vagina. Malignant transformation of endometriosis may occur in up to 1% of women, with the most common site being the ovary (1). The risk of ovarian cancer increases among patients with a long history of ovarian endometrioma (2), and the malignant transformation of endometriosis may be affected by the hormonal changes associated with menopause (3, 4) Endometriosis is present in 10% to 15% of patients with ovarian cancer, with the most common extra-ovarian site of neoplastic transformation being the rectovaginal septum (5). Forty patients with endometriosis-associated intestinal tumors have been reported (6-7), but malignant transformation of endometriosis in the uterine cervix is exceedingly rare.

In this report, we describe a woman with endometrioid adenocarcinoma arising from endometriosis of the uterine cervix. In addition, we review the literature on this condition, and discuss the prognostic factors and the most appropriate therapeutic approaches.

A 48-yr-old woman complaining of severe dysmenorrhea was referred for investigation of a pelvic mass. She was otherwise well, was not taking hormone medication, and had a body mass index of 24.4 kg/m². A cervical smear revealed benign cellular changes. Magnetic resonance imaging showed an image typical of an endometrial cyst of the uterine cervix, with high intensity in T1W1 and T2W1, a smooth surface, and shading. Adenomyosis was observed in the body of the uterus, but there was no evidence of enlarged lymph nodes or ascites (Fig. 1). Her serum concentration of CA125 was 359 U/mL (normal <35 U/mL). At the time of laparotomy, she had an enlarged uterus (12×7×6 cm³), which weighed 231 g, and her uterine cervix was enlarged to the size of an egg, with multiple round masses. Severe adhesion was observed, with endometrial tissue in the posterior wall of the uterus and the peritoneum and total posterior cul-de-sac obliteration. The left ovary was adherent to the posterior surface of the uterus, with a dark brownish cyst typical of an endometrial cyst. Total abdominal hysterectomy and bilateral salpingo-oophorectomy with adhesiolysis were performed, and the specimens were submitted for frozen section analysis. The extra-ovarian lesions were electrically cauterized. Pathologic examination of the frozen sections suggested an adenocarcinoma arising from endometriosis in the cervical wall.

On gross examination, the cervical wall of the uterus contained a relatively well defined, cystic lesion filled with dark brown fluid, measuring 3×2.2×2.2 cm. The dark brown colored inner surface of the cyst showed multi-focal, papillary growing, solid and granular masses, measuring up to 0.8×0.8×0.5 cm (Fig. 2). Microscopically, these masses were composed of well differentiated endometrioid adenocarcinoma, which was directly adjacent to the epithelium of the endometriotic cyst of the cervical wall. Transitional areas between the glandular epithelium of the endometriosis and the endometrioid adenocarcinoma cells were observed. There was no invasion to the cervical stroma and no connection between the overlying mucosal epithelium of the endo-ectocervix and the epithelium of the endometriosis or the adenocarcinoma. A secretory phase endometrium measured 0.8 cm in thickness. There was no evidence of a primary endometrial or endocervical adenocarcinoma in the endocervix or endometrium (Fig. 3). Multiple foci of endometriosis were present within the posterior wall of the uterus and both ovaries. A serous cystadenoma was also present in the right ovary, measuring 4.0 cm in greatest dimension.

The expression of estrogen and progesterone receptors, p53 and c-erb B-2 was analyzed using paraffin immunohistochemistry. The area of endometrioid adenocarcinoma was positive for both estrogen and progesterone receptors. Weak expression of p53 and c-erbB2 (10-20% of nuclear staining) was observed in the carcinomatous area. The patient was diagnosed as having an endometrioid adenocarcinoma arising from endometriosis of the uterine cervix. Following recovery from surgery, she was treated with six courses of chemotherapy, consisting of cyclophosphamide 600 mg/m² and cisplatin 50 mg/m² every 4 weeks.

At the present time, she has been clinically free of disease for 24 months since undergoing surgery.

Endometriosis of the cervix is generally regarded as a rare lesion, but its incidence has been as high as 2.4% in some series (8). Previous trauma to the cervix may contribute to this condition. For example, cervical endometriosis has been observed in 43% of postconization hysterectomy specimens obtained from patients with cervical intraepithelial neoplasia (CIN) recurrence and other conditions (not endometriosis) (9). Therefore, the increasing incidence of invasive cervical procedures may increase the incidence of endometriosis. Cervical smears taken from most patients with cervical endometriosis have shown glandular cellularity (10, 11). In contrast, a cervical smear taken from our patient before exploration showed normal features. There was no invasion to the stroma of the cervix, or to the mucosal layer of the endocervix or exocervix.

Neoplastic transformation is a rare complication of endometriosis, documented in 0.3-0.8% of patients with ovarian endometriosis (7). Of 147 women with pelvic endometriosis, only one had ovarian cancer arising from the endometriosis (0.7%) (12). The risk of cancer arising from pre-existing endometriosis has been estimated at 0.7% to 1.0% (1). Of neoplasms complicating endometriosis, 75% arise in the ovaries, with the majority (almost 70%) being of endometrioid type.

Malignant ovarian tumors have been documented in women with endometriosis. Endometriosis-associated ovarian cancer (EAOC) usually occurs in younger women, has favorable outcomes, and appears as either a low-grade tumor of endometrioid cell type or as a clear cell tumor. As the pathologic features of "atypical endometriosis" may constitute a precancerous state, women with atypical endometriosis may be at an increased risk of developing EAOC. Malignant changes have also been diagnosed in extragonadal endometriosis. For example, a survey of 45 extragonadal malignancies associated with endometriosis in 1977 found that 16 (36%) were in the rectovaginal area, 5 (11%) in the colorectal area, 4 (9%) each in the bladder and vagina, 3 (7%) in the pelvic ligaments, and 2 (4%) each in the umbilicus, cervix, and fallopian tube (13). A more recent survey of 27 malignancies associated with endometriosis found that 17 (62%) were in the ovary, 3 (11%) in the vagina, 2 (7%) each in the fallopian tube or mesosalpinx, pelvic sidewall, and colon, and 1 (4%) in the parametrium (14); this report, however, did not include cervical malignancies associated with endometriosis. Malignant transformation of extra-ovarian endometriosis is thought to account for approximately 25% of all malignant transformations of endometriosis (1, 15).

Because of the rarity of malignant transformation of endometriosis at extraovarian sites, including the cervix, it is difficult to design an optimal surgical procedure. When feasible, however, primary surgical treatment should consist of complete resection of all disease containing tissue. Gross lesions in the pelvis should be surgically staged (1). Although postoperative treatment has not been clearly defined, 70% of these patients have been reported to receive chemotherapy or radiotherapy after first line surgery (1, 15).

The 5-yr survival rate for patients with estrogen-stimulated endometriosis-associated neoplasms arising at all sites has been reported to be 82% (1). Moreover, patients with endometrioid adenocarcinoma coexisting with endometriosis have a favorable prognosis (16).

To classify a malignancy as arising from endometriosis, strict histopathologic criteria need to be met (17). These include the demonstration of cancer arising in the tissue and not invading it from another source, and the presence of tissue resembling endometrial stroma surrounding the epithelial glands. Microscopic endometriosis contiguous with the malignant tissue should also be demonstrated. Our patient met all these diagnostic criteria.

The risk factors for malignant transformation in endometriosis are poorly defined. Estrogen can stimulate the growth of ectopic endometrial tissue. Thus, if any ovarian tissue remains following a hysterectomy, the disease is likely to recur in as many as 40% of women after 5 yr (6, 18). In addition, an association has been noted between unopposed estrogen therapy and the development of endometrioid or clear cell epithelial ovarian tumors (19, 20). Of 21 women with extraovarian cancers arising in endometriosis, 13 (62%) had received hormone replacement therapy (HRT) (15). In contrast, only 10% of other groups of patients, including those with ovarian cancer arising within the endometriosis, ovarian cancer with adjacent endometriosis and ovarian cancer with incidental endometriosis, had received HRT, with the majority of the latter receiving unopposed estrogen. In addition, tamoxifen therapy has been associated with endometriosis and the exacerbation of endometriotic foci in postmenopausal women (21), and obesity may affect tumor development (22). However, the body mass index of our patient was 24.4 kg/m² and she had no previous history of estrogen or tamoxifen use. Also, our patient was 48 yr old and was premenopausal. Of three women with malignant tumors arising in endometriosis, 2 showed loss of ER and PR expression, suggesting that these tumors lose hormonal responsiveness as a result of malignant transformation (20). In contrast, the tumors in our patient showed consistent ER and PR expression, and she had no history of exposure to unopposed estrogen. These findings suggest that the loss of hormonal responsiveness did not play a part in the malignant transformation of endometriosis in our patient.

The increased association of HRT use with extraovarian cancer arising in endometriosis raises interesting questions that should prompt further investigation. Patients with endometrial cysts of the pelvic organs associated with high levels of serum CA125 should be managed with special care, even premenopausal women with no history of hormone therapy. Further work is required to determine whether the differences translate into a causal relationship. In conclusion, we present an extremely rare case of endometriosis-associated adenocarcinoma of the uterine cervix in a premenopausal woman. The clinical behavior of these tumors is unpredictable and long-term follow-up is essential in all patients. Additional case reports and prospective studies are needed to determine optimal treatment options to improve patient prognosis.