Perineal scar endometriosis ten years after Miles’ procedure for rectal cancer: Case report and review of the literature

1. Introduction Perineal scar endometriosis is a rare condition affecting young females at the episiotomy site following a previous vaginal delivery. Other scar sites, like Pfannesteil incision or trocar site incision, are frequently reported to be “usual”. Rarely, some general surgery procedures, being open or laparoscopic, can cause abdominal scar endometriosis. Frequently, the general surgeon is referred with these patients, though the surgical management of the disease does not pose challenges to the modern surgeon in terms of surgical technique but the disease itself can be sometimes misdiagnosed with other surgical conditions. We present a case of extrapelvic endometriosis arising within a perineal scar following a neoadjuvant pelvic radiotherapy and an abdominoperineal resection for a low rectal cancer. 2. Presentation of case A 35-year-old female presented at the Surgical Oncology Unit, Department of Oncology, “Garibaldi-Nesima” Hospital, complying of two subcutaneous nodules within her perineal scar. Ten years before, at a different institution, the patient underwent a neoadjuvant radiation treatment for a ypT2 G3 N0 M0 low rectal cancer. Since the tumor extended beyond the anal canal despite the previous neoadjuvant radiation therapy the patient received, she underwent an abdominoperineal resection at our institution. Further surgical and oncologic follow-up of the primary disease was unremarkable with the exception of two subcutaneous palpable nodules within the patient's perineal scar. These painless lesions were approximately 1 cm and 2 cm in diameter respectively, located the first near the posterior incisura of the vagina and the second within the otherwise well healed perineal scar. Surrounding skin was of normal appearance nor signs of local inflammation or discharge were present. Consistent with these findings, the nodules were deemed to be some retained suture material, so the asymptomatic patient was treated conservatively. The patient was constantly followed-up, as it is pertinent with the disease, and 5 years after the abdominoperineal resection she got pregnant. The pregnancy was regularly completed and the patient delivered a healthy girl via a previously planned caesarean section. After the post-partum period, when menses started occurring as usual, the patient returned to the Surgical Oncology Unit clinic because of a doubling in size of the known perineal nodules, this time being them tender and firm. Again, no signs of inflammatory changes were present. Indeed, the patient was extensively worked-up for recurrence of disease and every study turned out to be unremarkable. Due to the mild symptoms reported by the patient, once again we decided to treat her conservatively. Nine years after the Miles' operation, the patient got pregnant for the second time. During the second trimester the patient spontaneously aborted. One year later she presented to the Surgical Oncology Unit with a further enlargement of the two nodules having them become more painful and disabling. The patient underwent a soft tissue US and a pelvic CT scan to exclude a surgical site recurrence. The yield of these studies was unreliable (Fig. 1). At this stage the two pertinent working diagnoses consistent with history and physical of the patient were either local recurrent rectal cancer or scar endometriosis. Since our intent was to completely resect the mass in order to achieve a final pathologic diagnosis, the patient underwent a wide surgical excision of the perineal scar nodules en-bloc with the distal third of the posterior wall of the vagina. Furthermore, at surgery was noted a suspect 3 cm mass involving the tip of the coccyx, so an en-bloc, margin-free resection was achieved. The wound edges of the gap were loosely approximated. A series of dressings prepared by a wound-specialist nurse proved to be safe and effective in the healing process (Fig. 2). Recovery was uneventful. Final pathology report confirmed the endometrioid nature of the nodules, with coccyx involvement. At 10 months follow up the patient is doing well and is symptom-free. 3. Discussion Endometriosis is defined as an ectopic implantation of uterine mucosal tissue outside the uterine cavity. The disease affects nearly 10-15% of young fertile women, usually between 25 and 35 years of age. It is mostly an endopelvic disease and commonly occurs in the ovaries, cervix, uterine ligaments and pelvic peritoneum. Extrapelvic endometriosis is a relatively uncommon disease, accounting for approximately 12% of all cases. The pattern of involvement in extrapelvic endometriosis is rather different, since almost every organ has been described in the literature as a site of disease. The most common extrapelvic site of endometriosis is surgical scar area. Scar endometriosis can develop within and adjacent to surgical site of previous abdominal procedures, not surprisingly, the vast majority being gynaecological operations. The most common reported cases of scar endometriosis are related to caesarean section deliveries and hysterotomy for abortion. In a 1999 review by Honore, the incidence of scar endometriosis was noted to be 3.5% after the incision of the gravid uterus. The reported incidence after C-section ranges from 0.03% to 0.45%, being about 1% for mid-trimester abortion. Although the aetiology and pathogenesis of incisional endometriosis after both open and laparoscopic gynaecologic procedures are clear, they are much more less obvious after non-gynaecologic surgery. Indeed, scar endometriosis may rarely be seen after a number of general surgery procedures like appendectomy, inguinal herniorraphy, laparoscopic cholecystectomy and even laparoscopic gastric by-pass. There is a feeling the list will become wider and wider. Apparently, the route of surgery does not seem to alter the display of the disease since the number of reports of previous laparoscopic surgery is increasing in the late literature. At the authors' knowledge, no report of perineal scar endometriosis following abdominoperineal resection for rectal cancer has been published so far. Several theories exist for the development of endometriosis: metaplasia, retrograde menstruation, venous and lymphatic metastatization, and mechanical transposition. The latter mechanism is thought to be responsible for scar endometriosis. The great number of cases of incisional endometriosis occurring after opening of the gravid uterus, as well as the great trophic characteristics that make transplantation of endometrial tissue particularly successful within the surgical wound, are the stronger supporters of the mechanical transposition theory. In case of non-gynaecological abdominal surgery, seeding of pre-existing unknown intra-peritoneal endometriosis into the surgical wound is most probable. However, direct implantation of endometrial tissue cannot explain all 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. From an etiologic perspective, the present case can be explained with postoperative menstrual implantation within the open perineal wound resulting from the procedure. Another mechanism of transplantation would see silent foci of unknown, asymptomatic pelvic endometriosis that could have been present at the time of surgery and have been disseminated within the wound edges. These foci developed into overt disease several years after surgery. Of interest, the patient's pelvis was preoperatively irradiated and this issue deserves more study since we are unaware of the effects of radiation therapy on endometrial ectopic tissue. Noteworthy, the patient got pregnant five years following the abdominoperineal resection meaning that sacral nerves plexus, uterus, adnexa, and the birth canal were all respected during surgery, and neoadjuvant radiotherapy did not negatively affect the patient's fertility. This becomes particularly true when we look at the second pregnancy the patient started. Certainly, the vigorous hormonal changes due to the first pregnancy and, to a lesser degree to the second one, could have been involved in the development of the overt, symptomatic disease as outlined in the case history. Usually, diagnosis of scar endometriosis can easily be made clinically by a careful history and physical examination. Most of the patients present with a tender, palpable subcutaneous swelling near or within the surgical scar. The cyclic nature of the swelling and pain, which worsen at the time of menstruation, and a frequently reported history of gynaecologic or rarely non-gynaecologic abdominal surgery, are nearly pathognomonic. However, a high index of suspicion is required since a number of patients do not meet the classic triad of mass, cyclic pain, and previous incision. Almost half of the patients present with non-cyclic pain, or the latter is so severe and disabling that the patient is evaluated and treated as having an acute abdomen. Furthermore, the interval between the previous surgical procedure and symptoms is highly variable, being as long as 20 years. Differential diagnosis includes, but is not limited to, abscess, suture granuloma, neoplastic tissue, hernia, hematoma, hypertrophic scar tissue, traumatic neuroma, metastatic carcinoma. Specifically, in the present case a differential diagnosis was not easy since the previous surgery was performed for rectal cancer and the endometrioid nodules were within the perineal scar, conditions that prompted us to first think at the neoplastic nature of the mass. For this purpose the patient underwent US and CT of the site that proved to be unreliable in this specific case, even if CT and MRI seem to be useful in differential diagnosis. However, they generally do not provide definitive diagnosis. Preoperative fine-needle aspiration biopsy could have been useful but since the therapeutic algorithm would not change, we decided to obtain a final pathology report of the entire specimen. In fact, a diagnosis of endometriosis is satisfied if endometrial glands, stroma, and hemosiderin pigment are seen. Currently, local excision is the most appropriate treatment, and a wide excision with at least 1-cm free margin is considered treatment of choice in recurrent cases. Care must be exercised not to rupture the mass during surgery to avoid re-implantation or not to leave any remnants. Recurrence of scar endometriosis is a rare event, with few cases reported so far. Results showed that the size and extent of the mass are the only statistical prognostic factors for recurrence. Malignant degeneration of episiotomy scar endometriosis is also described. Large, deep and complex lesions involving full-thickness of the abdominal wall or the pelvic floor require complex resections and usually necessitate tissue transfer and/or synthetic mesh repair. Recently, a report describing serous papillary carcinoma arising in incisional abdominal wall endometriosis was published. This 56-year-old patient underwent a laparotomy for uterine perforation due to dilatation and curettage 20 years ago. After biopsy, neoadjuvant therapy was administered, followed by wide excisional surgery plus reconstruction, thus achieving a complete control of the disease. Similarly, anal-sphincter invading endometriosis has been published, with emphasis on reconstructive techniques and quality of life. Patients affected with scar endometriosis may simultaneously have some other forms of abdominal or pelvic disease, so they should be questioned about related symptoms and should be offered a gynaecologic follow-up. 4. Conclusion This unusual case presents some important associations not previously described (rectal cancer, neoadjuvant radiotherapy, abdominoperineal resection, pregnancy after pelvic irradiation and surgery, perineal scar endometriosis) and at the same time poses some relevant diagnostic challenges (perineal recurrent rectal cancer, perineal scar endometriosis). Conflicts of interest statement The authors have no conflicts of interest to disclose. Funding None. Ethical approval Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request. References - 1. Gunes M, Kayikcioglu F, Ozturkoglu E, Haberal A. Incisional endometriosis after cesarean section, episiotomy and other gynecologic procedures. J Obstet Gynaecol Res 2005;31:(5)471–475 - 2. Martínez-Serna T, Stalter KD, Filipi CJ. 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