A rare omental tumor presenting as pelvic mass – A case report

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Benign multicystic mesothelioma (BMCM) of omentum and peritonium is a rare intra-abdominal lesion of unknown etiology. Incidence is more common in females of child-bearing age group. Rarity of this tumor and non-specific symptoms causes preoperative diagnostic dilemma. Precise diagnosis requires immunohistochemistry study. Despite of high recurrence rate, aggressive surgical excision is the treatment of choice. Our case report of BMCM is a rare as it was detected in a young male patient and there was involvement of omentum only.

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A rare omental tumor presenting as pelvic mass – A case report

  1. 1.                                                                                                                                             A rare omental tumor presenting as pelvic mass - A case report 
  2. 2. Case Report A rare omental tumor presenting as pelvic mass e A case report Diwakar Sahu, Somak Das, Majid R. Wani, Prasanna K. Reddy* Apollo Hospital, Greams Road, Chennai, India a r t i c l e i n f o Article history: Received 24 July 2014 Accepted 29 July 2014 Available online xxx Keywords: Omental tumor Benign multicystic mesothelioma Mesothelioma a b s t r a c t s Benign multicystic mesothelioma (BMCM) of omentum and peritonium is a rare intra- abdominal lesion of unknown etiology. Incidence is more common in females of child- bearing age group. Rarity of this tumor and non-specific symptoms causes preoperative diagnostic dilemma. Precise diagnosis requires immunohistochemistry study. Despite of high recurrence rate, aggressive surgical excision is the treatment of choice. Our case report of BMCM is a rare as it was detected in a young male patient and there was involvement of omentum only. Copyright © 2014, Indraprastha Medical Corporation Ltd. All rights reserved. 1. Introduction Primary omental tumors are very rare as compared to meta- static tumors. Benign multicystic mesothelioma (BMCM) is a rare form of tumor arising from cellular lining of abdominal cavity. The most common site is the peritoneum followed by uterus, ovary, bladder, rectum or retro-peritoneum. Incidence is more common in females of child-bearing age (83%) and in most cases, there will be an associated history of previous abdominal surgery, pelvic inflammatory disease or endome- triosis.1 Unlike pleural mesothelioma, peritoneal type is not related to asbestos exposure.2 Pathogenesis is controversial and two hypotheses have been proposed which are reactive and neoplastic.1,3 Recurrence rate after surgery is reported to be quite high (33e50%).4 BMCM usually presents with symptoms due to pressure effects of massive lesion including abdominal pain, fullness & distension. Definite diagnosis is made with a combination of histopathology and immunohistochemistry.5 2. Case report A 19 year old male patient presented with a history of inter- mittent mild abdominal pain since two years and fullness of lower abdomen for last six months. On examination, an abdominal lump of size 15 Â 12 cm was palpable occupying the hypogastrium and extending into the pelvis. Consistency was firm with smooth surface, ill defined margins and mini- mal side to side mobility. Routine blood investigations showed no obvious abnormality. Serum level of tumor markers including CEA, CA19-9, AFP and CA-125 were within normal limits. Ultrasound abdomen reported a large cystic anechoic lesion with multiple internal septations. CT abdomen revealed a diffuse cystic lesion in pelvis which was reaching * Corresponding author. E-mail address: drpkreddyapollo@gmail.com (P.K. Reddy). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/apme a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1 e3 Please cite this article in press as: Sahu D, et al., A rare omental tumor presenting as pelvic mass e A case report, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.07.017 http://dx.doi.org/10.1016/j.apme.2014.07.017 0976-0016/Copyright © 2014, Indraprastha Medical Corporation Ltd. All rights reserved.
  3. 3. upto umbilical level with thin septations with no significant enhancement after contrast [Fig. 1]. No infiltration into bladder, sigmoid colon & small bowel was reported and impression of lymphangioma of lower half of omentum was made. So, based on CT scan finding, strongly favoring a benign tumor, patient was posted for surgery. During laparotomy, a large 20 Â 16 cm multi-loculated mass involving the lower half of omentum was found [Fig. 2]. It was adherent to anterior abdominal wall, urinary bladder & sigmoid colon and con- sisted of multiple locules or cysts (1e5 cm in diameter) with a thin translucent wall and clear watery content. The tumor was occupying almost whole of the pelvis and there was no infiltration into bladder or colonic wall. Adhesions were released & complete excision of tumor was done [Fig. 3]. His- topathological examination was suggestive of a multicystic lesion, lined by clusters of mesothelial cell, with abundant eosinophilic cytoplasm & hobnail appearance [Fig. 4]. So, diagnosis of a benign multicystic lesion was made with possibility of benign multicystic mesothelioma and omental lymphangioma. Subsequently, immunohistochemistry (IHC) was done for confirmation which showed positive staining for cytokeratin, calretnin, CK7 and WT1. Also, staining was negative for CD31, CD34 and CK20. Ultimately based on IHC, diagnosis of benign multicystic omental mesothelioma was made. Post operative recovery of the patient was uneventful and after six months of surgery, there are no signs of recurrence or any complications. 3. Discussion Mesothelioma arises from the epithelial and mesenchymal component of the mesothelium. Omentum is composed of two layers of mesothieal cells and most of tumors arising from it, including BMCM, are mesenchymal in nature. Benign multicystic mesotheioma involving the peritonium was first described in 1979 by Mennemeyer and Smith.6 As mentioned, Fig. 1 e CT scan showing multicystic lesion involving omentum. Fig. 2 e BMCM of omentum. Fig. 3 e Specimen of BMCM. a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1 e32 Please cite this article in press as: Sahu D, et al., A rare omental tumor presenting as pelvic mass e A case report, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.07.017
  4. 4. it occurs mainly in women of child-bearing age but cases of BMCM have been reported in children and adults. Pathogen- esis is mainly inflammatory in origin as tumor microscopi- cally reveals inflammatory features and there will be history of endometriosis or PID and abdominal surgery. In view of the progressive growth pattern, large tumor size and tendency to recur after surgery, some authors consider that origin of tumor is neoplastic.1,4 According to inflammatory origin the- ory, chronic irritation causes peritoneal reaction in form of entrapment of mesothelial cells, leading to reactive prolifer- ation and multiple cyst formation.4 Role of female sex hor- mones has been implicated in its pathogenesis as it is more common in females and few case reports show ER & PR expression.7 Grossly, BMCM is characterized by multiple cysts filled with mucinous or clear fluid ranging from several mm to >20 cm in diameter. Few cases of malignant transformation have been reported and it is characterized by destructive growth with infiltration of the entire omentum or adjacent organs, cellular atypia and increased mitotic count.1,4,8 Preoperative diagnosis is often difficult. CT scan is the most useful diagnostic modality and BMCM is characterized by well-defined, low-attenuation mass with non-enhancing septa. Also, it gives information regarding involvement of adjacent organs and cyst's contents, thus helps to determine feasibility of resection.9 Definite diagnosis is made with the combination of histopathology and immunohistochemistry. Histopathology will show multicystic lesion lined by a single layer of cuboidal cells of mesothelial origin along with septa- tions containing fibromuscular stroma and inflammatory cells. Immunohistochemistry will demonstrate positive staining for mesothelial origin markers like calretinin, cyto- keratin, CK7 and WTA.1,5 The differential diagnosis include lymphangioma, pseu- domyxoma peritonei and carcinomatosis peritonei. Lym- phangioma intimately resembles BMCM and usually characterized by a large, thin-walled and muliloculated cystic mass. Content of lymphangioma cyst is predominantly chylous (but may be serous or hemorrhagic). Microscopic ex- amination shows cystic spaces lined by a single layer of flat- tened endothelial cells and stroma contains smooth muscle and aggregates of lymphocytes.10 IHC is positive for CD31þ, CD34þ and factor VIIIþ.1 Recurrence is very low after surgery. Treatment option for BMCM is complete and aggressive surgical excision including cytoreductive surgery with peri- tonectomy. Continuous hyperthermic peritoneal perfusion with cisplatin or doxorubicin and peritonectomy has also been described.1,5,7 There are reports of use of tamoxifen and GnRH analogs (e.g leuprolide) to reduce cyst volume and cyst growth but results are variable.7 Due to relatively high recur- rence rates of BMCM, follow-up imaging is advised, especially after incomplete surgical excision. Prognosis is excellent with very low mortality.4 To conclude, benign multicystic mesothelioma of omen- tum is a very rare benign tumor, which is seldom diagnosed on preoperative imaging. Diagnosis requires histological & immunohistochemistry evaluation. Treatment consist of aggressive complete surgical excision. Conflicts of interest All authors have none to declare. r e f e r e n c e s 1. Safioleas MC, Constantinos K, Michael S, Konstantinos G, Constantinos S, Alkiviadis K. Benign multicystic peritoneal mesothelioma: a case report and review of the literature. World J Gastroenterol. 2006;12:5739e5742. 2. Inman DS, Lambert AW, Wilkins DC. Multicystic peritoneal inclusion cysts: the use of CT guided drainage for symptom control. Ann R Coll Surg Engl. 2000;82:196e197. 3. Weiss SW, Tavassoli FA. Multicystic mesothelioma. An analysis of pathologic findings and biologic behaviour in 37 cases. Am J Surg Pathol. 1988;12:737e746. 4. Dieniecka Monika, Kału_zynski Andrzej. Benign multicystic peritoneal mesothelioma. Pol J Pathol. 2011;2:122e124. 5. Petrou G, Macindoe R, Deane S. Benign cystic mesothelioma in a 60-year-old woman after cholecystectomy. ANZ J Surg. 2001;71:615e618. 6. Mennemeyer R, Smith M. Multicystic, peritoneal mesothelioma: a report with electron microscopy of a case mimicking intra-abdominal cystic hygroma (lymphangioma). Cancer. 1979;44:692e698. 7. Letterie GS, Yon JL. The antiestrogen tamoxifen in the treatment of recurrent benign cystic mesothelioma. Gynecol Oncol. 1998;70:131e133. 8. Giles TD, Henderson JC, Dominguez GH. Diffuse malignant mesothelioma of the peritoneum. South Med J. 1967;60:63e66. 9. Pitta X, Andreadis E, Ekonomou A, et al. Benign multicystic peritoneal mesothelioma: a case report. J Med Case Rep. 2010;4:385. 10. Rao TN, Parvathi T, Suvarchala A. Omental lymphangioma in adults-rare presentation report of a case. Case Rep Surg. 2012;2012:629482. Fig. 4 e HPE showing multicystic lesion lined by mesothelial cell. a p o l l o m e d i c i n e x x x ( 2 0 1 4 ) 1 e3 3 Please cite this article in press as: Sahu D, et al., A rare omental tumor presenting as pelvic mass e A case report, Apollo Medicine (2014), http://dx.doi.org/10.1016/j.apme.2014.07.017
  5. 5. Apollohospitals:http://www.apollohospitals.com/ Twitter:https://twitter.com/HospitalsApollo Youtube:http://www.youtube.com/apollohospitalsindia Facebook:http://www.facebook.com/TheApolloHospitals Slideshare:http://www.slideshare.net/Apollo_Hospitals Linkedin:http://www.linkedin.com/company/apollo-hospitals Blog:Blog:http://www.letstalkhealth.in/

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