**3. Malignant transformation**

54 Endometriosis - Basic Concepts and Current Research Trends

The etiology and pathogenesis of endometriosis are complex and still incompletely

1. Implantation theory. Theory of implantation was described by Sampson in 1921 (Sampson JA, 1921). Retrograde menstruation (Sampson's theory) occurs possibly as a result of a hypotonic uterotubal junction in women with endometriosis, allowing increased menstrual regurgitation. Endometrial cells shed from the uterus at menstruation spread in a retrograde manner passing along the fallopian tube to the peritoneal cavity. This theory would account for by far the highest incidence of

2. Coelomic metaplasia. Under the influence of certain unspecified stimuli, mesothelial

3. Transplantation of exfoliated endometrium. Lymphatic, vascular and iatrogenic routes may disseminate endometriosis. Transtubal regurgitation is the most common route. 4. Altered immunological recognition of endometrial tissues allowing acceptance of emboli of endometrium in these sites. Probably a combination of the first and last theories is most likely to be responsible for endometriotic lesions in different sites of the

Transplantation theory actually is divided from the first theory (implantation theory). During vaginal delivery, viable endometrial cells become implanted in the perineum, including the site of episiotomy and result in endometriotic lesions. Perineal lesion often occurs during vaginal delivery, but the incidence of PEM is rare. The reasons for rare incidence may include: (1) Bacteria existing in the perineal wound which can cause infection or even necrosis of the local tissues. The infection and necrosis is not appropriate for transplanted endometrial cells to live. (2) After delivery, the level of estrogen decreases,

We reported one case of PEM with no history of surgical manipulation or trauma of her perineal area. Perineal endometriosis without history of delivery can not be explained by transplantation theory. We tried lymphatic dissemination theory on this patient (Zhu et al., 2003). As there are rich lymphatic communications between uterus, cervix, vaginal and perineum, endometrial tissues can be transported by lymphatic routes and result in perineal

Nicola Cinardi et al., reported a special case of perineal scar endometriosis ten years after Miles' procedure for rectal cancer. The patient was a 35-year-old-female who was treated 10 years earlier at the same institution for a low rectal cancer. She presented with two discrete subcutaneous bulges within her perineal wound. Since the patient was asymptomatic and the complete work up for recurrent disease showed no evidence of malignancy, first line therapy was conservative. After two pregnancies and a caesarean section, the patient presented at our observation with enlarged and tender perineal nodules. The patient was treated with a wide excision of the perineal scar en-bloc with the nodules. Final pathology report was consistent with perineal scar endometriosis. In the report, the author suggests that direct implantation of endometrial tissue cannot explain all the cases. There are a variety of cases of primary cutaneous endometriosis without previous abdominal surgery at different sites such as umbilicus, vulva, perineum, groin, and extremities (Healy et al., 1995;

**2. Pathogenesis** 

body.

endometriosis.

understood. So many theories have been developed:

endometriosis occurring in the pelvis.

cells might undergo a metaplastic change to endometrium.

which also makes the growth of transplanted endometrial cells difficult.

There is a growing awareness of risk of possible transformation of endometriosis into an invasive malignancy. This is rare but well documented, and theoretically, it can occur in any gonadal or extragonadal site of endometriosis. Since 1925, more than 200 cases of malignant transformation of endometrioma have been reported in the literature (English). Heaps et al. found that 79% of such cases occurred in the ovary, the reminder occurring in extragonadal sites, usually in rectovaginal septum, pelvic peritoneum, colon, rectum, and vagina. The 5 year survival rate in patients with localized disease treated with surgery and postoperative radiation is about 80% (Heaps et al., 1990). Malignant transformation of extraovarian endometriosis is uncommon and only 60 cases have been reported world widely until 1990; of them, ninety percent are endometroid carcinomas (Johana et al., 2007).

Johana Castillo Bustamante et al. reported a 41 year-old female patient with an episiotomy in her delivery and a myomectomy performed at 31 year-old. She had symptoms for a year like progressive pain and tumour at the perineum and glutei area and cyclic bleeding. The core biopsy reported endometrioid carcinoma of perineum. She was diagnosed of "1. Pelvic tumour: Hematometra or ovarian tumour; 2. Solid tumour of right isquiorrectal area: endometroid carcinoma". When laparotomy was performed, the uterus was absent, a left ovarian endometrioma cyst and a right follicular cyst were detected, and appendix had endometrial tissues. Six months after the surgery the patient had liver metastases and she died 2 months later (Johana et al., 2007).
