In 1952, Willson and Peale described LPD for the first time[6]. LPD characterized with multiple nodules in various sizes in peritoneal cavity, such as uterus, fallopian tubes, intestine, mesentery, omentum and retroperitoneum[6]. The incidence of LPD was unkown due to its rarity. There have been no more than 200 cases reported in the literature up to date.
LPD was difficult to diagnose before surgery. Although it was a benign disease with excellent prognosis, LPD could behave quasi-malignant behavior, such as recur tendency and spread widely in pelvic and abdominal cavity. LPD should be differentiated from peritoneal metastasis of malignancies. Standard histopathological analysis as well as immunochemistry was in need to diagnose LPD accurately. Microscopically, the knots are composed of smooth muscle arranged like leiomyomas, and the cells usually show a lack of atypia and higher mitotic variety[9]. In this study, the patient was suspected to have malignant tumors in pelvic and peritoneal cavity initially and was eventually diagnosed with LPD by histopathology. LPD must be distinguished from malignancies to avoid unnecessary aggressive treatment schedules.
LPD predominantly occurs in females of reproductive age, however, the pathogenesis of LPD is poorly understood. High levels of estrogen and progesterone, such as oral contraceptives, pregnancy, ovarian stimulation, estrogen-producing ovarian tumors and uterine leiomyoma, have been described in most reported cases[5, 9, 12-15]. In this case with pregnancy, high levels of estrogen and progesterone stimulation also played an essential role in the development of LPD. Besides, the tumor cells were strongly positive for ER and PR in immunochemistry analysis, supporting the hypothesis that high levels of estrogen and progesterone playing an important role in the pathogenesis of LPD.
Immunohistochemical analysis of this case showed that SMA and Desmin were strongly positive, suggesting that LPD has similar molecular cytogenetic characteristics with uterine leiomyoma. However, LPD differentiates distinctly from uterine leiomyoma in phenotype. Uterine leiomyoma is obviously benign, whereas LPD has the quasi-malignant behavior. NGS might provide the potential molecular explanation that would explain this difference in phenotype. Compared with common population, CNs of CDK4, MYC, NBN, DAXX were all amplified for at least 4 times in this LPD. Immunochemistry of the four genes among uterine leiomyoma, LPD and uterine leiomyosarcoma was implied. LPD and uterine leiomyosarcoma both were moderately and strongly positive for the four genes mentioned above, whereas uterine leiomyoma was slightly positive or negative. CNs mutations might play an important role in the pathogenesis mechanism of LPD and identify LPD in phenotype from uterine leiomyoma. Further study is in urgent need to delineate the molecular mechanisms underlying the LPD phenotype. In addition, some literatures have confirmed that LPD will be followed by malignant transformation[16-18]. Based on the above results, we should pay attention to the potential malignancy of LPD during the treatment and follow-up of LPD.
Most importantly, we will discuss the feasibility and safety of pregnancy in patients with LPD. We searched PubMed database with key words of “leiomyomatosis peritonealis disseminata”, “peritoneal leiomyomatosis”, “leiomyomatosis”, “disseminated fibrosing deciduosis”, “LPD”, “pregnancy” and “pregnant”. Sixteen cases of LPD during pregnancy with detailed clinical and follow-up information published from 1973 to 2012 were included for analysis[9, 13, 19-31], and the details were available in Table 3. The patient's age was between 22-40 years old, and the history of pregnancy and childbirth seems to have no obvious correlation with the occurrence of LPD. There were three patients with a history of hysteromyoma resection, which may be one of the causes of LPD[20, 21, 29]. Ten cases of LPD patients without obvious clinical symptoms were delivered at full term[13, 19, 20, 23-27, 30, 31], therefore, for the patients without obvious symptoms, close follow-up could be conducted without surgical treatment, but the patients should be fully informed of possible complications and malignant changes in the tumor. LPD was accidentally diagnosed in ten patients during cesarean section due to obstetric reasons, such as fetal distress, abnormal labor process, and vulvar hematoma, and these complications were not directly related to LPD[13, 19, 20, 23, 25-28, 30, 31]. Abdominal pain is the most important complication of LPD during pregnancy, which may be related to the rapid growth and compression of the lesions[9, 22, 29]. The huge volume of LPD lesions could lead to abnormally increased pressure in the amniotic cavity, so PROM was relatively common[9, 19, 24], and in our case, the maximum diameter of the tumor reached 20cm. LPD that occurred during pregnancy does not appear to have a significant adverse effect on newborns, except for complications related to preterm delivery[22, 24].
In previous reports, LPD lesions could naturally shrink or disappear after delivery, and the tumor did not relapse during the reported follow-up period[19, 28, 31], therefore, for patients without fertility requirements, radical surgery was unnecessary. However, there was limited literature on how patients with subsequent fertility requirements should be treated. The patient reported by Deering was diagnosed with LPD before pregnancy, and the lesion rapidly increased in a short period of time after receiving IVF - ET, suggesting that assisted reproductive technology may induce the occurrence and progress of LPD[29]. Lim OW reported a case of a pregnant patient with LPD who underwent only nodules biopsy at the first cesarean section, and the patient developed PROM at 35weeks and recurrence of the LPD at the second pregnancy[24]. In our report, we suffered great difficulty and risk of complete removal of all visible lesions during the first cesarean delivery, and no lesions in pelvic and abdominal cavity in the second cesarean section were found, suggesting that complete resection of the lesion may be beneficial for the subsequent pregnancy. However, more patients are needed to confirm this conclusion.
Finally, we will discuss the significant risk of LPD patients receiving assisted reproductive technology. In the case reported by Tanaka YO, the patient previously underwent laparoscopic myomectomy, followed by IVF-ET, and had a cesarean section due to twin pregnancy. LPD biopsy was performed during cesarean section.However, the patient's lesions continued to increase, and finally received total hysterectomy and lesions resection 8 months after delivery, and no disease progression was found after 18 months of follow-up[21]. In the case reported by Deering S, the patient had a history of LPD and confirmed the existence of the disease before receiving IVF-ET. After receiving IVF-ET, the lesions in the pelvic and abdominal cavity increased rapidly, and severe hydronephrosis occurred due to tumors compression. The pregnancy was terminated at 10 weeks of pregnancy because of the intolerance of the patient and more potential risks. The patient was treated with methotrexate and leuprolide, but the tumor did not shrink significantly, finally, the patient underwent total hysterectomy and bilateral appendectomy, and radical resection of the lesions. In the subsequent follow-up, no recurrence of the disease was found[29]. The above two medical records reminded us that IVF-ET was a high-risk factor for LPD and could cause serious consequences. Assisted reproductive technology should be used with caution in this group of people.
In conclusion, LPD is an unusual intermediate between benign and malignant uterine smooth muscle tumors. We recommend that all visible lesions should be removed as completely as possible during surgery, which may be a very effective treatment plan in addition to radical surgery, and re-pregnancy may be feasible. Besides, assisted reproductive technology should be used with caution in LPD patients.