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Journal of Pathology of Nepal (2021) Vol. 11, 1864 - 1867
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Case Report
Benign multicystic peritoneal mesothelioma: a
case report
Rashmi Sharma1, Shobha Verma2, Devanshi Desai3, Renu Malhotra1,
Ranjana Desai4
Govind Diagnostic Clinic, Jodhpur, India
Dr. Shobha Verma Hospital, Bali, India
3
Jawaharlal Nehru Medical College, Belgaum, India
4
Dr. Sampurnanand Medical College, Jodhpur, India
1
2
Keywords:
Calretinin;
Mesothelioma;
Multicystic;
Peritoneum;
Pelvic inflammatory
disease;
ABSTRACT
Free-floating peritoneal masses found during laparotomy should arouse a suspicion of benign multicystic
peritoneal mesothelioma and they must be removed and subjected to histopathological examination and
immunochemical staining to ascertain their benign nature. The objective of the study was to report a
rare case of benign multicystic peritoneal mesotheliomas. We report an incidental finding of multiple
free-floating peritoneal masses in a pregnant primigravida woman with a normal antenatal course who
underwent a cesarean section in a rural hospital setting in India for fetal distress. The masses were removed
from the peritoneal cavity during the surgery and subjected to histopathological examination and found
to be benign multicystic peritoneal mesotheliomas. Immunohistochemistry of the cysts revealed that the
mesothelial cells lining the cysts were positive for calretinin and WT1 and negative for CD31.
Correspondence:
Dr. Rashmi Sharma
Govind Diagnostic Clinic, Sardarpura, Jodhpur – 342003, India
ORCID ID: 0000-0002-0783-269X
Email :drrashmisharmamd@gmail.com
Received : May 25th 2020 ; Accepted : September 30th 2020
Citation: Sharma R, Verma S, Desai D, Malhotra M, Desai R. Benign Multicystic Peritoneal
Mesothelioma: A Case Report. J Pathol Nep 2021;12(2):1864-7. DOI: 10.3126/jpn.v11i2.29114
Copyright: This is an open-access article distributed under the terms of the Creative Commons
Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction
in any medium, provided the original author and source are credited.
INTRODUCTION
Benign multicystic peritoneal mesotheliomas (BMPM)are
rare accidental findings in a laparotomy procedure and are
usually seen in young women of their reproductive age.1
They are often associated with prior pelvic surgeries2,
pelvic inflammatory diseases2, endometriosis.3 They may, at
times, complicate pregnancy or may be the cause of acute
abdomen.4 Though considered benign they are prone to
recurrence and estrogen can modulate their growth because
of the presence of estrogen receptors within the cysts.5 Until
now very few cases have been reported in the literature.
When encountered during a routine laparotomy, they present
an unusual perplexing diagnostic challenge to a surgeon
who is unprepared to see lesions other than for which the
DOI : 10.3126/jpn.v11i2.29114
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Sharma R et al.
Figure 1:(a) Gross appearance of one of the tumor masses. It is white in color with a smooth surface and paper-thin walls. (b) The cut section of a cyst
shows that the walls are very thin and the cyst was filled with watery fluid.
primary surgery was indicated. We report this case because
of its rarity and the accidental nature of finding them during
a routine cesarean section in an asymptomatic patient and
the need to recognize it as an obfuscating but benign lesion
encountered during routine laparotomy.
and WT1 (fig.2c) and negative for CD31 (fig.2d). Therefore
the diagnosis of benign multicystic mesothelioma was
confirmed and upheld.
CASE REPORT
Benign cystic mesothelioma, also called multicystic
mesothelioma, is a rare tumor that usually occurs in
women of reproductive age group. Since they are usually
asymptomatic, they are difficult to diagnose preoperatively.6
In our case the patient was a primigravida, married for
one and half years, and had no complaints of the disease,
which may, sometimes, clinically present as acute/ chronic
abdominal pain.1,3,7
A 26-years healthy primigravida was subjected to a
cesarean section at term because of a reduction in a
fetal heartbeat. There was no prior history of surgery,
endometriosis, or inflammatory disease in this patient. She
had been asymptomatic during the entire antenatal period
and had normal antenatal ultrasound findings. At the time
of cesarean section, multiple free-floating masses of size
7 x 4 x 2 and 5 x 4 x 2 cm were seen in the peritoneum
which were readily picked up, preserved, and sent for
histopathological examination as they were a source of
perplexity and concern to the operating surgeon. A healthy
female child was delivered. After the closure of the uterus
and abdomen, the patient made an uneventful recovery.
The gross examination of the material received consisted
of multiple cystic structures collectively measured 9 x 7 x
2 cm. The external surface of the cysts was smooth (fig.1a)
The cyst walls were papery thin and on cutting the cysts,
they extruded clear fluid mixed with whitish gelatinous
material (fig. 1b). Microscopic examination with routine
hematoxylin and eosin stain revealed multiple thin-walled
cysts lined by mesothelial cells and containing eosinophilic
fluid (fig.2a). There were mild inflammatory cells in
the stroma between the cysts with foci of mesothelial
cell hyperplasia. Hence, the diagnosis of benign cystic
mesothelioma/multicystic mesothelioma was made.
However, also considering lymphangioma and malignant
mesothelioma as differentials, the tumor was subjected to
immunohistochemistry which revealed that the mesothelial
cells lining the cysts were positive for calretinin (fig. 2b)
DOI : 10.3126/jpn.v11i2.29114
DISCUSSION
This tumor was first described by Menemeyer and Smith.8
Though considered benign these tumors are prone to
recurrence.5 They arise from epithelial and mesenchymal
elements of the mesothelioma cells and do not metastasize.
They appear as multicystic lesions from the surface of the
pelvic viscera, the serosal surface of the intestine, omentum,
retroperitoneal space, spleen, and liver. Solitary masses can
be seen arising from the basal pleura.9 They are usually
large, maybe multifocal or unilocular. They can also be seen
as free-floating cysts10 as in our case. Microscopically, the
cysts are thin-walled and may contain eosinophilic fluid.
The mesothelial cells lining the cyst may vary from flattened
to endothelial-like to cuboidal. Inflammatory cells are often
present within the stroma between cysts, along with focal
mesothelial hyperplasia.11
The pathogenesis of the tumor has been widely debated
regarding its inflammatory or neoplastic origin. Some
attribute it to inflammatory processes because of its coexistence with pelvic surgeries, endometriosis, and recurrent
pelvic infections.3 But currently its neoplastic origin is
favored because the incidence of its association with
previous surgeries is low, and there is no preponderance of
Benign multicystic peritoneal mesothelioma
1866
Figure 2:(A) (Top Left) Multiple thin-walled cysts lined by mesothelial cells and containing eosinophilic fluid. There were mild inflammatory cells in
the stroma between cysts with foci of mesothelial cell hyperplasia ( HE stain, X50). (B) Immunohistochemistry of tissue shows that the mesothelial
cells lining the cysts are positive for Calretinin. (D) Immunohistochemistry showing mesothelial cells of the cysts are positive for WT 1. (D)
Immunohistochemistryshowing mesothelial cells of the cysts are negative for CD 31.
BMPM with abdominal infections.
A large case series undertaken to elucidate the role of
hormone receptors in the genesis of this tumor has found
that two cases were positive with estrogen receptors which
indicates its neoplastic origin.5 Estrogen receptor positivity
also impacts the growth and recurrence risk of this tumor
which is high; approximately 40 to 50 %. The present
case also hints towards a neoplastic origin. Our patient
was pregnant and it is well known that both estrogen and
progesterone levels are elevated during pregnancy and
estrogen can trigger the neoplastic process.5
It has also been suggested that estrogen receptor-positive
multicystic peritoneal mesotheliomas respond to tamoxifen
therapy which makes it mandatory to test this tumor for
the presence of estrogen receptors.5 In the present case,
however, the estrogen receptor study was not done. It’s also
pertinent to note here that the presence of this tumor in male
patients precludes the use of tamoxifen.
These tumors grow slowly and progressively in untreated
lesions and may recur after surgical resection. Rarely,
they may be associated with an adenomatoid tumor
which is again a benign mesothelial tumor of unresolved
etiopathogenesis, whether neoplastic or hyperplastic. Some
authors suggest that BMPM represents borderline lesion
between adenomatoid and malignant mesothelioma.6,7
Differential diagnosis of this tumor is most commonly with
adenocarcinoma, lymphangioma, malignant mesothelioma,
well-differentiated papillary mesothelioma, abdominal
carcinomatosis in endometriosis, cystic ovarian neoplasm,
and pseudomyxoma peritonei. Immunohistochemistry for
benign multicystic mesothelioma is calretinin positive and
also positive for WT-I, CK 7, and CK 5/6 but negative for
CD 31.12,13 Lymphangiomas occur in younger patients and
may contain chylous fluid which is grossly evident in the
cut section of the tumor. Histologically they show lymphoid
aggregates and smooth muscle within their walls and are
CD 31 positive. Cystic teratomas contain adipose tissue and
DOI : 10.3126/jpn.v11i2.29114
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Sharma R et al.
calcifications.11,14
Mesenteric cysts, omental cysts, and pseudocysts are often
confused with benign multicystic mesotheliomas. But they
are usually unilocular with no distinct cyst wall or internal
septa and they are keratin and calretinin negative.
Pseudomyxoma peritoneal (mucinous peritoneal) metastasis
may have coexisting omental laking, soft tissue peritoneal
nodules, scalloping of serosal margins of the liver or spleen.
Loculated ascites has an irregular border and are surrounded
by bowel loops or abdominal/ pelvic organs. Malignant
mesothelioma is desmin negative but P53 positive, EMA
and CEA positive. Peritoneal endometriosis is a condition
that produces peritoneal cysts. These cysts are not freefloating and are fibrotic and hemorrhagic and should not be
confused with cystic mesotheliomas.15
7.
Akbayir O, Gedikbasi A, Akyol A. Benign cystic mesothelioma: a
case series with one case complicated by pregnancy. J ObstetGynaecol
Res, 2011;37:1126-31. Crossref
8.
Gonzalez-Moreno S, Yan H, Alcorn KW et al. Malignant
transformation of Benign cystic mesothelioma of the peritoneum. J
Surgical Oncology 2002; 79;243-51. Crossref
9.
Tentes A -A, Zorbas G, Pallas N. Multicystic Peritoneal mesothelioma.
The American journal of case reports 2012;13:262-4. Crossref
10.
Park JY, Kim KW, Kwon H et al. Peritoneal mesotheliomas:
Clinicopathological features, CT findings and differential diagnosis.
Am J Roent., 2008;191;814-25. Crossref
11.
Somasundaram S, Khajanchi M, Vajas T et al. Benign Multicystic
Peritoneal Mesothelioma: A Rare Tumor of the Abdomen. Case
reports in surgery.2015; Article ID 613148,1-3. Crossref
12.
Cury PM, Butcher DN, Fischer C etal. Value of mesothelium
associated antibodies thrombomodulin, cytokeratin, 5/6 calretinin
and CD 44 H in distinguishing epithelial pleural mesotheliomas from
adenocarcinomas metastatic to pleura. Mod. Pathol 2000;13:107-12.
Crossref
13.
Daglionic, Dei Tos AP, Laurino L, et al. Calretinin a novel
immunohistochemical marker for mesothelioma. AMJ. Surg Pathol
1996;1037-46. Crossref
14.
Chua TC, Yan TD, Morris DL. Surgical biology for the clinician:
peritoneal mesothelioma: current understanding and management.
Canadian Journal of Surgery, 2009;52;59- 64. Website
15.
Clement PB. Pathology of endometriosis. PatholAnnu1990;25:245-95.
Website
CONCLUSIONS
In conclusion, BMPM is an oddity that can present as
an incidental finding of multiple free-floating peritoneal
cysts during routine laparotomy surgery, and should not
be a source of concern and perplexity for the operating
surgeon as they are benign lesions. When such free-floating
peritoneal masses are encountered during laparotomy,
they should arouse a suspicion of BMPM and they must
be removed and subjected to histopathological examination
and immunochemical staining to ascertain their benign
nature.
Conflict of interest: None
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