Benign Multicystic Mesothelioma Presenting as a Cause of Chronic Pelvic Pain

Introduction

Chronic pelvic pain affects nearly 15% of women annually in the United States. The etiology of chronic pelvic pain is multifactorial and may include extrauterine causes. Peritoneal cystic lesions of mesothelial origin are quite rare pathologies and are generally considered recurrent lesions. The only therapy is a surgical one, and it permits differential diagnosis to distinguish between cystic mesothelioma and other peritoneal lesions.

Case

A 40-year-old woman (gravida 6, para 2) presented with a 6 month history of intermittent pelvic pain that had recently worsened over the previous 2 weeks, had become constant severe pelvic pain including difficulty with voiding and bowel movements. The patient had been seen in the emergency room 4 days previously, at which time a computed axial tomography (CAT) scan of the abdomen and pelvis showed a 5.2×4.7 cm multiloculated pelvic mass posterior to the bladder and extending along the left pelvic side wall just posterior to the left external iliac vein.

The patient had no significant past medical history. Her past surgical history included a total abdominal hysterectomy 3 years prior for endometriosis, multiple breast lump excisions, and wisdom tooth extraction.

She had no significant family history and smoked a pack of cigarettes a day.

Findings from her respiratory, cardiovascular, and abdominal examinations were normal. A pelvic examination revealed a 6 cm firm tender mobile left adnexal mass. She was scheduled for a laparoscopic unilateral salpingo-oophorectomy.

She underwent a diagnostic laparoscopy, which showed normal tubes and ovaries but a 4 cm×4 cm pelvic mass adherent to the left pelvic side wall, small bowel, and appendix, and obliterating the posterior cul-de-sac. She had a normal gallbladder, liver margin, and peritoneal surfaces. An intraoperative consultation was obtained with a colorectal surgeon who converted the laparoscopy to a laparotomy, excision of the pelvic mass, appendectomy, and enterolysis. Pathology confirmed a benign multicystic mesothelioma (BMM), a normal appendix, and peritoneal fluid negative for malignancy.

Discussion

BMM is an uncommon lesion of the peritoneum occurring predominantly in women of reproductive age. BMM is also referred to as “multicystic peritoneal mesothelioma,” “cystic mesothelioma of the peritoneum,” “multilocular cyst of the peritoneum,” “multicystic mesothelioma,” and “multilocular peritoneal inclusion cyst,” and is an uncommon lesion of the peritoneum characterized by the formation of multiple, thin-walled, multilocular cysts that frequently produce large, intra-abdominal masses, and which often recurs after surgical resection. The lesion occurs most frequently in women with a history of previous abdominal surgery, endometriosis, or pelvic inflammatory disease, although there are cases involving men and preadolescent children, as well as rare extra-abdominal cases, which are well documented. ¹ Debate continues as to whether the disease process in BMM is primarily reactive or neoplastic in nature, but the fact that the great majority of patients are women of reproductive age suggests a key role for female sex hormones in the disorder's pathogenesis, although there have reported cases in postmenopausal women.^1,2

BMM was first described by Mennemeyer and Smith in 1979, ³ with the largest case series of 17 patients being that of Sawh et al. in 2003. BMM, a localized tumor arising from the epithelial and mesenchymal elements of mesothelial cells, does not metastasize, but, however, has a strong predilection for the surface of the pelvic viscera. When the tumor is found in the peritoneal cavity, lesions are found intimately attached to the serosal surfaces of the intestine or omentum, or in the retroperitoneal space, spleen, and liver. In this case, BMM was adherent to the small intestine, cecum, and appendix, and mimicked a malignant pathology, which led to a laparotomy being performed.

The clinical presentation of BMM is varied from being an asymptomatic, incidental finding during other surgery, a reported case of incarcerated epigastric hernia, lower abdominal pain, abdominal or pelvic mass, or abdominal distension.

BMM is thought to be primarily reactive or neoplastic in nature. The close relationship with inflammation, a history of prior surgery, endometriosis, or uterine leiomyoma suggests that it is probably as a result of a peculiar reaction to chronic irritation stimuli, with mesothelial entrapment, reactive proliferation, and cystic formation, with microscopic examination confirming these findings of inflammation. ²

Another theory of its pathogenesis is related to BMM being neoplastic in nature. This is based on a slow but progressive growth of untreated lesions, a marked tendency to recur after surgical resection, a low incidence of previous abdominal infection, and a high disease-related mortality. ⁴ Malignant transformation of BMM is an unusual occurrence, indicating a neoplastic nature underscoring the necessity of long-term follow-up. ⁵ In no cases had there been exposure to asbestos.

Pathologic differential diagnoses include a wide variety of both benign and malignant lesions that may present either as cystic or multicystic abdominal masses. Benign lesions include cystic lymphangioma, cystic forms of endosalpingiosis, endometriosis, Mullerian cysts involving the retroperitoneum, cystic adenomatoid tumors, and cystic mesonephric duct remnants. Malignant lesions that may mimic BMM are rare cystic variants of malignant mesothelioma, serous tumors involving the peritoneum, and ovarian clear cell carcinomas with microcystic architecture. ¹

In most patients, the diagnosis is made incidentally during examination or laparotomy for other reasons. Radiologic tests including ultrasound, computed tomography (CT), and magnetic resonance imaging can demonstrate the lesion.

Surgery is the only effective treatment for BMM. Complete removal of the cystic lesion is the mainstay of treatment and the only hope for avoiding local recurrence. Aggressive surgical approaches including cytoreductive surgery and peritonectomy are recommended. ⁶ BMM is amenable to laparoscopic approach, however, in cases in which the lesion is adherent other abdominal viscous, recourse to open surgery may reduce the chance of further injury. Recurrences occur more frequently in women and can be shown by CT-guided cystic aspiration and treated by hormonal therapy with antiestrogens, ⁷ gonadotropin-releasing analogues, ⁸ hyperthermic intraperitoneal chemotherapy, ⁹ and sclerotherapy with tetracycline, ¹⁰ and the degree of success of all these treatment modalities varies.

Conclusions

In conclusion, BMM is a rare lesion of uncertain pathogenesis and malignant potential. When diagnosed, complete excision, cytoreductive surgery, and peritonectomy are recommended to avoid local recurrence. This patient, to date, has not shown any signs of recurrence since her index surgery one year ago.