Incidental fallopian tube mesothelioma diagnosed at time of elective bilateral salpingectomy for sterilisation: A case report

Written informed consent was obtained from the patient for publication of this case report. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

The authors declare that there are no conflicts of interest.

Mesothelioma is a rare primary tumour of the female genital tract, most commonly with a benign natural history though potential for benign recurrence locally ( Horn and Leqis, 1951 ). This tumour was favoured to represent mesothelioma due to combined presence of calretinin, CK 5/6, D2 40, WT 1 and PAX 8, as PAX8 has been previously observed by mesothelioma experts in intra-peritoneal lesions ( Kawai et al., 2016 , Laury et al., 2010 ). Ovarian papillary serous and clear-cell tumour are documented to show stronger PAX8 activity though the absence of BerEP4, mCEA, oestrogen receptor, progestogen receptor and desmin make these tumours less likely in this case. Mesotheliomas of the female genital tract are currently described as a tumour of uncertain malignant potential primarily due to only a small number of reported cases and limited knowledge of its' biological behaviour ( Malpica et al., 2012 , Rivera, 2008 ). The differential diagnosis includes mesothelial hyperplasia, malignant mesothelioma, and serous tumour of low malignant potential ( Malpica et al., 2012 ). In this case, no specific risk factor could be identified, as the patient had no confirmed history of asbestos or other pollutant exposure, no previous history of radiation, no endometriosis and the tumour demonstrated retention of normal BAP1 activity. In this literature review no cases of malignant mesothelioma were found originating from a fallopian tube primary. In a case series of 26 patients with well-differentiated papillary mesothelioma there was one report of recurrence ( Malpica et al., 2012 ) (primary site omental mesothelioma at time of resection of ovarian cystadenofibroma). The patient was asymptomatic and the recurrence was discovered incidentally during a later colectomy for colonic adenocarcinoma. However, several cases of mesothelioma at other peritoneal sites and uterine mesotheliomas have demonstrated malignant potential. These are largely symptomatic lesions which involve multiple sites, are associated with ascites, and have high-grade nuclei ( Goldblum and Hart, 1995b ). As such, until further evidence can be determined into the natural history of fallopian tube mesotheliomas specifically, a conservative approach may be safest with recommendation to proceed to total hysterectomy and bilateral oophorectomy and consideration of pelvic washings ( Goldblum and Hart, 1995b ). This report aims to contribute to the study of rare neoplasms of the female genital tract so that a more accurate incidence and natural history may be determined.

The patient was referred to a tertiary Gynaeoncology department for review. Their advice in conjunction with the reporting pathologists was to proceed to total hysterectomy and bilateral oophorectomy, which the patient underwent under the Gynaeoncology team with no complications. Histopathology from this returned normal uterus with two fibroids confirmed and normal ovaries with nil evidence of mesothelioma. The patient recovered well post-operatively and was referred to the respiratory service for review regarding likelihood of further mesothelioma.

Mesothelioma is a well-known malignancy arising from mutations in mesothelium, a simple squamous epithelium arising from the embryonic mesoderm ( UpToDate topic, 2016 ). Pleural mesothelioma is most well known and is most commonly linked to an exposure to industrial pollutants, primarily asbestos. There are also documented cases of primary mesothelioma arising in the parietal peritoneum and the genital tract though these are rare, representing only 10–15% of mesothelioma cases in the United States annually ( UpToDate topic, 2016 ). Mesothelioma is a very uncommon primary tumour of the female genital tract, usually with a benign natural history though with the potential for benign recurrence locally ( Schneider et al., 1961 ). On literature review, the first documented case appeared in 1913 ( Horn and Leqis, 1951 ) with most documented cases occurring the in uterus corpus ( Mourali et al., 2010 ). However, cases have infrequently been reported in fallopian tubes with three specific cases found as described in Table 1 ( Malpica et al., 2012 , Paoletti, 1951 ) and an additional 11 cases reported in a literature review of an early publication in 1951 ( Horn and Leqis, 1951 ). In one case series of genital tract mesothelioma, the disease was shown to primarily affect young Caucasian women with a mean age of 30 ( Schneider et al., 1961 ) whilst another case series showed a mean age of 48.6 ( Malpica et al., 2012 ). It is commonly asymptomatic and is often discovered incidentally at time of laparotomy/laparoscopy for other indication as in this case, or at autopsy ( Bofetta, 2007 ) ( Fig. 1 , Fig. 2 , Fig. 3 ). Fig. 1 Non-encapsulated lesion adjacent to fallopian tube. Fig. 1 Fig. 2 Tumour with solid sheets, papillary and tubular areas. Fig. 2 Fig. 3 Tumour with tubular and papillary architecture, with cuboidal uniform appearing cells and scattered concretions consistent with psammoma bodies. Fig. 3 Table 1 Previously documented cases of fallopian tube mesothelioma and outcomes. Table 1 Patient/year Presentation Histopathology Treatment 1 ( Chen et al., 2012 ) 1961 TAH LSO for Lower abdominal pain, dysmenorrhea and dyspareunia Cystic mesothelioma of uterine fundus, left and right adnexa, cul-de-sac, and sigmoid colon; endometriosis of left ovary and peritoneum N.B. Patient presented with widespread disease involving fallopian tube Diagnosed at time of planned TAH BSO. Nil evidence of recurrence at 3 years 2 ( Kawai et al., 2016 ) 1961 Mesothelioma of the Salpinx Nil details available 3 ( Laury et al., 2010 ) 2012 Incidental finding during hysterectomy for leiomyoma Chronic xanthogranuloma-tous salpingiosis Planned hysterectomy. Nil further treatment Non-encapsulated lesion adjacent to fallopian tube. Tumour with solid sheets, papillary and tubular areas. Tumour with tubular and papillary architecture, with cuboidal uniform appearing cells and scattered concretions consistent with psammoma bodies. Previously documented cases of fallopian tube mesothelioma and outcomes. There is a strong relationship between asbestos exposure and the development of mesothelioma at any location. However, the link between asbestos exposure and extra-pleural mesothelioma is less strong than it is for pleural mesothelioma, particularly among women ( Bofetta, 2007 ). Other reported risk factors include radiation therapy at the site, exposure to other mineral fibres including erionite ( UpToDate topic, 2016 ) or a history of endometriosis ( Malpica et al., 2012 ). There have been reports of peritoneal mesotheliomas containing sequences of the papovavirus, simian virus 40 (SV40), however the causal nature of the association has been questioned ( Rivera, 2008 ). It has also been noted that a tumour suppressor gene previously identified in pleural mesothelioma, BRCA-associated protein (BAP) 1, is frequently mutated in extra-pleural mesothelioma ( Rivera, 2008 ). This is a case report of a 42 yo female who underwent elective laparoscopic bilateral salpingectomy for unwanted fertility, which returned an incidental finding of a localised mesothelioma.

Macroscopic examination revealed a white nodule measuring 10 × 6 mm adjacent to the fimbriae of the left fallopian tube. Microscopic examination revealed a discrete, relatively well circumscribed though non-encapsulated lesion composed of cuboidal/polyclonal cells with no evidence of significant cytological atypia. The cells were arranged in sheets with areas of papillary and tubular architecture. The papillary structures had hyalinised stromal cores. Up to 3 mitotic figures per 10 high-power fields were identified. No atypical mitotic figures were seen. Ki67 showed a low proliferative index of < 5%. No atypical mitoses were evident. Scattered psammoma bodies were present. There appeared to be some hyaluronic acid production, which was highlighted with Alcian blue and largely lost with hyaluronidase pre-digestion. The tumour cells expressed calretinin, CK 5/6, D2 40 and WT 1 and were negative for BerEP4, mCEA, oestrogen receptor, progestogen receptor and desmin. The lesional cells retained expression of BAP1 and demonstrated diffuse intermediate to strong expression of PAX 8. This lesion was regarded as benign and of mesothelial origin but was not typical of a well-differentiated papillary mesothelioma of the peritoneum. A provisional diagnosis of mesothelioma was made based on the morphology and the immunoperoxidase results ( Chen et al., 2012 , Goldblum and Hart, 1995a , Sugarbaker et al., 2016 ). Expert opinions from a Respiratory Pathologist and mesothelioma expert were also obtained. The consensus was that this is a mesothelial lesion and as this appeared clinically to be a localised lesion with no other evidence of intraperitoneal disease, a diagnosis of localised mesothelioma was made ( Goldblum and Hart, 1995a ).