Metastatic Malignant Mesothelioma Research Articles

Oral metastasis of pleural sarcomatoid mesothelioma, a rare aggressive variant of mesothelioma and a diagnostic challenge

<h3>Introduction</h3> Malignant mesothelioma is a rare neoplasm that most commonly develops after exposure to asbestos and arises from the serosal cells of the pleura or rarely peritoneum. Various histological subtypes have been recog- nized: epithelioid, sarcomatoid, biphasic-epithelioid, and biphasic-sarcomatoid, with the sarcomatoid variant being a less common, but more aggressive variant. Numerous genetic alterations have been identified in the development and progression of malignant mesothelioma, most notably mutations in tumor suppressor genes, <i>neurofibromatosis type 2 (NF2), BRCA1-associated protein-1 (BAP1),</i>and <i>cyclin-dependent kinase inhibitor 2A/alternative reading frame (CDKN2A/ARF)</i>. Mesothelioma metastasis to the oral cavity is infrequent, with only nineteen cases reported in the literature. Soft tissue involvement of the oral cavity has been reported in the tongue, followed by the mandibu- lar gingiva, and alveolar mucosa. Prognosis for malignant mesothelioma is poor as it is typically unresponsive to conventional chemotherapeutic agents. New targeted therapies are currently in ongoing clinical trials. <h3>Case Findings</h3> An 81-year-old male, undergoing treatment for malignant pleural mesothelioma and with a history of asbestos exposure, presented for evaluation of a raised, necrotic mass on the left posterior mandibular buccal and lingual gingiva. Panoramic radiograph revealed extensive bone loss. The histopathology was that of a sarco- matoid neoplasm. Immunohistochemistry demonstrated positive staining for WT1, cyclin D1, and P53, supporting the diagnosis of metastatic malignant mesothelioma, sarcomatoid variant. Other stains that help to define mesothe- lioma such as CK5/6, calretinin, and D2-40 were negative. Despite equivocal immunostaining results, the diagnosis was further supported by comprehensive genomic analysis with identification of mutated <i>NF2</i>and <i>BAP1</i>tumor sup- pressor genes. <h3>Conclusion</h3> The diagnosis of malignant pleural mesothelioma relies on morphology supplemented with immuno- histochemistry. The diagnosis is challenging, especially so for the sarcomatoid variant, with immunohistochemical staining profiles often being inconsistent. The current case demonstrates the utility of comprehensive genomic analysis in firmly establishing the diagnosis.

Treatment of Platinum Nonresponsive Metastatic Malignant Peritoneal Mesothelioma With Combination Chemoimmunotherapy.

Malignant peritoneal mesothelioma is a rare cancer associated with minimal durable disease control with chemotherapy and poor overall survival. The efficacy of combined cytotoxic chemotherapy and immune checkpoint inhibitors (ICIs) in malignant peritoneal mesothelioma has not previously been studied. We describe the clinical course of 2 patients with metastatic peritoneal mesothelioma who both relapsed with platinum nonresponsive disease after initial cytoreductive surgery and chemotherapy. In both cases, addition of pembrolizumab to platinum and pemetrexed treatment resulted in a substantial partial and a near complete disease response. Notably, both patients possessed tumors without validated biomarkers of ICI response, including low tumor mutational burden and negative programmed death ligand-1. The unique genomic landscape of each patient may have enabled increased tumor immunorecognition and ICI efficacy. In addition, chemotherapy priming of the tumor microenvironment may have improved ICI response. This report supports future research to characterize the benefit of combination chemotherapy and ICI in peritoneal mesothelioma.

Symptomatic Cerebral Metastases In Malignant Pleural Mesothelioma: A Rare Case Report

Abstract Casestudy: Malignant mesothelioma is an aggressive tumor with dismal prognosis. Incidence in the United States is approximately 3300 cases/year, and the most common site is the pleura. Although mesothelioma is usually a locally invasive tumor, distant metastases to liver, adrenal glands, kidney and contralateral lung have been described. Brain metastases are observed in less than 3% of metastatic cases and most have been detected incidentally at autopsy. Symptomatic brain metastases are unusual. We describe a case of a 77 year old gentleman with history of occupational asbestos exposure who presented with shortness of breath and dry cough. The radiological investigations revealed left pleural thickening with pleural effusion, which on biopsy proved to be biphasic malignant mesothelioma. Despite multi-modality therapy, the patient showed local disease progression. Following 37 months of initial diagnosis, he developed progressive left-sided weakness. Brain MRI revealed a 1.7 cm enhancing mass involving right posterior frontal lobe, with extensive edema in the surrounding tissue. On biopsy, mass was composed of nests and sheets of round-to-spindled cells with scant eosinophilic cytoplasm, separated by fibrous septa. Brisk mitotic activity and necrosis were present. There was a sharp border with adjacent brain parenchyma. The tumor was positive for WT-1, calretinin, and cytokeratins and negative for Ber-Ep4 and glial fibrillary acid protein by immunohistochemistry. The histological appearance of the tumor was similar to that of the pleural biopsy. Thus a diagnosis of metastatic malignant mesothelioma was made. This solitary metastasis was treated with resection and post-operative stereotactic radiation. The 3-month follow-up brain MRI revealed nodular enhancement within the cavity with multiple supra- and infra-tentorial enhancing lesions, and leptomeningeal enhancement, most consistent with progressing metastatic disease. With the advancements in treatment options that has improved survival in malignant mesothelioma patients, the pathologist and neurosurgeon should be aware of the diagnostic possibility intra-operatively which may alter the management.

S2812 A Rare Case of Small Bowel Obstruction Mimicking Crohn’s Disease

INTRODUCTION: Mesothelioma is an uncommon, but feared malignancy. Its peritoneal variant is an even rarer entity and is classified based on 3 histologic subtypes: sarcomatoid, epithelioid, and biphasic. The sarcomatoid variant carries the worst prognosis. CASE DESCRIPTION/METHODS: A 26-year old female presented with a 6-month history of recurrent abdominal pain, nausea, loose stools, and unintended weight loss. Her past medical history was significant for squamous cell carcinoma (SCC) of the tongue which was treated with surgical resection including lymph node dissection with plans for adjuvant chemotherapy/radiation after evaluation of her gastrointestinal symptoms. She underwent extensive workup that included labs, stool studies, EGD, colonoscopy, and MR enterography; resulting in a presumed diagnosis of Crohn's disease based on endoscopic, but not histologic, evidence of ileitis. She was referred to our inflammatory bowel disease center, and a plan to repeat colonoscopy and ileoscopy with biopsies was made after seeing our GI and surgical subspecialists. Before outpatient workup could be completed, the patient presented emergently with nausea, reduced flatus, and reduced stooling. CT showed distal small bowel obstruction due to abnormal thickening of 5–10 cm of the terminal ileum with mucosal enhancement and extensive wall edema and inflammation of the adjacent mesenteric fat. Inpatient colonoscopy with ileoscopy revealed mild erythema and edema of the terminal ileum and sigmoid colon. A non-traversable, smooth appearing stricture was encountered 5 cm proximal to the ileocecal valve. The endoscopic appearance was not consistent with Crohn's disease. Ileal biopsies revealed prominent lymphangiectasia and associated erosion of overlying mucosa, and sigmoid colon biopsies were normal. Due to worsening symptoms, a diagnostic laparoscopy was performed, revealing an extraluminal, 6–7 cm that compressed the terminal ileum and was adherent to the sigmoid colon. She underwent an ileocecal resection with primary anastomosis. Final pathology revealed metastatic malignant mesothelioma of the sarcomatoid variant. She recovered well from surgery and is undergoing oncologic care. DISCUSSION: Our case demonstrates a unique presentation of a rare, clinically challenging entity that mimicked a typical presentation of Crohn’s disease.Figure 1.: CT Abdomen/Pelvis.Figure 2.: Terminal Ileal Biopsy with dilated lymphatic spaces and overlying eroded mucosa- 4x.Figure 3.: Terminal Ileal Biopsy with dilated lymphatic spaces and overlying eroded mucosa- 10x.

10P Gender differences in molecular-guided therapy recommendations for metastatic malignant mesothelioma

10P Gender differences in molecular-guided therapy recommendations for metastatic malignant mesothelioma

The value of BRCA-1-associated protein 1 expression and cyclin-dependent kinase inhibitor 2A deletion to distinguish peritoneal malignant mesothelioma from peritoneal location of carcinoma in effusion cytology specimens.

Diffuse malignant peritoneal mesothelioma (DMPM), represents 30% of all malignant mesothelioma, and is characterised by a difficult diagnosis and different presentations. Immunohistochemistry has improved the diagnostic sensitivity and specificity in the differential diagnosis between metastatic adenocarcinoma and malignant mesothelioma, and loss of BRCA-1-associated protein 1 (BAP1) expression is correlated with BAP1 somatic or constitutional genetic defects. Furthermore, cyclin-dependent kinase inhibitor 2A (CDKN2A) is frequently lost in DMPM. In the present study, we assessed the value of integrating BAP1 in the panel of antibodies used for the diagnosis of DMPM in cytological samples. Since p16 fluorescent in situ hybridisation (FISH) assay could constitute an additional useful adjunct, results of BAP1 immunostaining and p16 FISH assays have been compared. Forty-eight DMPM patients and 71 peritoneal carcinomatosis patients were included. BAP1 immunohistochemical and CDKN2A FISH techniques were performed on tissue specimens of DMPM (n=48) and peritoneal carcinomatosis (n=71) then on cell-block of DMPM (n=16), peritoneal carcinomatosis (n=25) and peritoneal benign effusion (n=5). Loss of BAP1 expression was observed in 56.3% of DMPM while none of the peritoneal carcinoma specimens showed BAP1 loss of expression. CDKN2A loss was observed in 34.9% DMPM and 2.1% peritoneal carcinoma. Although BAP1 immunostaining was successful in 100% of cytological DMPM samples, CDKN2A deletion status could be obtained for 75% of DMPM cases. BAP1 immunostaining represents an objective and reproducible diagnostic biomarker for peritoneal mesothelioma in effusion cytology specimens and should be preferred to CDKN2A FISH analysis on these precious samples.

MA23.07 Loss of Expression of BAP1 and/or MTAP Aids in the Diagnosis of Malignant Mesothelioma Metastatic to Lymph Nodes

Stage and histology are the strongest prognostic parameters in malignant pleural mesothelioma and aid management of patients. However, the distinction between reactive intranodal mesothelial cells and metastatic malignant mesothelioma (MM) can be challenging. Loss of BRCA1 associated protein-1 (BAP1) and/or methylthioadenosine phosphorylase (MTAP) expression has been identified in a subset of MM but not in reactive mesothelial proliferation. We investigated the value of these markers in the distinction between reactive mesothelial cells and metastatic MM in lymph nodes. Surgical files of Mayo Clinic Rochester (1996-2018) were searched for metastatic MM in lymph nodes. All cases and if available corresponding primary MM were reviewed by a thoracic pathologist (ACR) to confirm the diagnosis. Primary MM and lymph nodes were stained with BAP1 (clone C-4) and MTAP (2G4). Absence of nuclear staining of BAP1 and absence of nuclear and cytoplasmic staining of MTAP in essentially all tumor cells was considered as loss of expression. Forty-four patients (25 males, 56.8%) had a median age of 64 years (range, 24-75) at time of surgery. Tissue was available from nodal metastases in all cases, either paired with the primary MM at time of nodal sampling (N=37) or at a different time (N=4) (time between tissue collections, range, 1day- 4 years, respectively), or without paired primary MM (N=3). Thirty-seven pleural, 6 peritoneal and 1 pericardial MM were of epithelioid (N=39) or biphasic (N=5) subtype. Patients underwent extrapleural pneumonectomy (N=17), pleurectomy (N=7), resection (N=9), debulking (N=2), biopsy (N=8), or autopsy (N=1). In nodal metastases, BAP1 and/or MTAP expression was lost in 29 (of 43, 67.4%) cases; specifically, BAP1 expression was lost in 28 (of 44, 63.6%), MTAP was lost in 14 (of 43, 32.6%), and both were lost in 12 (of 43, 27.9%) cases. Agreement in expression/loss of expression of BAP1 and/or MTAP in primary and metastatic MM occurred in all cases. During a median follow up of patients who underwent extrapleural pneumonectomy or pleurectomy (available in N=23) of 14.8 months (range, 1-119) 17 patients died within a median time of 16 months. BAP1 and MTAP immunostains are helpful in the distinction between metastatic MM and reactive mesothelial cells in lymph nodes when one or both markers lost expression in the mesothelial cells. Expression of both markers does not exclude the possibility of metastatic MM.

Diagnostic value of medical thoracoscopy in malignant pleural effusion

BackgroundMedical thoracoscopy has been shown to be an efficacious procedure in diagnosing unexplained exudative pleural effusions with excellent safety. This study aimed to assess the diagnostic significance of thoracoscopy in the management of patients with malignant pleural effusion (MPE).MethodsConsecutive patients with malignant pleural effusion were retrospectively reviewed, and their demographic, radiographic, thoracoscopic and histological data were collected.ResultsBetween July 2005 and June 2014, 342 of 833 patients undergoing thoracoscopy were finally confirmed to suffer from MPE. The top three frequent causes of MPE were metastatic carcinoma (79.5%), malignant mesothelioma (10.2%), and lymphoma (2.9%). Among metastatic malignancies, the most common cancer was lung cancer (85.2%), followed by breast cancer (4.4%), ovarian cancer (2.2%), pancreatic cancer (1.8%), etc. No serious adverse events associated with thoracoscopy were recorded.ConclusionsMedical thoracoscopy is a valuable and safe tool in diagnosing malignant pleural effusion with minimal complication rates.

Clinical and pathological characteristic of metastatic malignant mesothelioma initially diagnosed by lymph node biopsy

BackgroundIt is a great challenge for pathologists to initially diagnose metastatic malignant mesothelioma (MM) by the lymph node biopsy without any history of primary MM. Because the onset of MM is hidden and the metastatic MM in lymph node is relatively uncommon. Besides, morphologic and immuohistochemistry features of MM are similar to other tumors. MethodsIn order to improve the initial diagnostic accuracy of metastatic MM from LN biopsy and to reduce or avoid the possibility of missed diagnosis or misdiagnosis, we had collected the clinical and pathological data of the metastatic MM cases in our department, and summarized the characteristics of morphological, immunohistochemical and fluorescence in situ hybridization (FISH) results. ResultsSeven patients (4 males and 3 females) with 21–73 year-old had been included in our study. Six cases showed serous cavity effusion, serosal thickening and systemic multiple lymph node enlargement. The “moderate, nice” tumor cells were arranged in variable patterns. Mitosis was hardly to be found and necrosis was absent. Four immunohistochemical staining panels and FISH detection had been used for diagnosis and differential diagnosis of MM. All cases expressed broad-spectrum epithelial markers and at least 2 mesothelial-cell-origin markers. None were positive for specific-tissue-origin markers, and all cases were diagnosed of malignancy according to immunohistochemical markers and detection of pl6 gene deletion. ConclusionIt is necessary for us to keep our awareness of metastatic MM in lymph node. Correct diagnosis of MM metastasis by lymph node biopsy were based on detailed understanding of the clinical manifestation and the image data, careful observation of morphologic characteristics, and properly using immunohistochemical markers or FISH detection if necessary for diagnosis and differential diagnosis.

Metastatic Malignant Mesothelioma Presenting With Cardiogenic Shock

Metastatic tumor progression to the pericardium is generally characterized by pericardial effusion with or without tamponade. It is extremely rare for tumor to metastasize to the pericardium and cause constrictive pericarditis and tamponade physiology. We report a case of metastatic malignant mesothelioma admitted to our facility for acute hypoxic respiratory failure and cardiogenic shock due to extensive pericardial metastasis and trapped heart. This was confirmed during post-mortem evaluation, which showed malignant mesothelioma involving the anterior mediastinum and partially encasing the heart and the root of the aorta in addition to fibrous pericarditis and pericardial adhesion. J Med Cases. 2017;8(2):58-60 doi: https://doi.org/10.14740/jmc2739w

Metastatic malignant pleural mesothelioma masquerading as a case of acute abdomen secondary to small bowel perforation

Metastatic pleural mesothelioma is a rare disease. The present study aimed to report a rare presentation of metastatic malignant mesothelioma (MM). The patient was an elderly man who presented with small bowel (jejunal) perforation secondary to metastatic pleural mesothelioma deposits. This was a rare presentation of a rare disease and the first reported case in the published studies in which MM masqueraded as bowel perforation prior to the primary diagnosis.

Métastases révélatrices de mésothéliomes malins du péritoine : difficultés diagnostiques à propos de deux cas et conduite à tenir

Peritoneal malignant mesothelioma is a rare and extremely aggressive tumor that is sometimes difficult to diagnose. We report two cases of metastatic malignant peritoneal mesothelioma. In one case, malignant metastatic cells were identified in cervical lymph nodes while in the other case, the cells were found in the liver. In both cases, metastases were identified before discovering the primary tumor. This led to the misdiagnosis of carcinoma of unknown origin. Nevertheless, the histological and immuno-histochemical patterns were typical of malignant mesothelioma. Regarding metastasis of unknown origin, a differentiation of epithelioid peritoneal malignant mesothelioma and adenocarcinoma proved to be difficult. Therefore, we discuss the diagnostic usefulness of immuno-histochemical mesothelioma markers.

5. Benign mesothelial inclusions in a mediastinal lymph node in association with previous cardiac surgery: a case report

Mesothelial inclusions in mediastinal lymph nodes are uncommon and are a great mimic of metastatic carcinoma or malignant mesothelioma. Several studies have shown that inclusions are mostly found in lymph nodes draining regions of pleural effusions or pericardial effusions from various causes. Our case report illustrates that the finding of mesothelial inclusions can also be associated with previous cardiac surgery. The mechanism of lymph node seeding by these benign mesothelial cells is thought to be migration of the mesothelial cells via lymphatics as part of post surgical inflammatory processes. It is important to be aware of the possibility of mesothelial inclusions in lymph nodes to avoid overdiagnosis of metastatic carcinoma or malignant mesothelioma.

Clinicopathological characteristics of pulmonary epithelioid hemangioendothelioma: A report of four cases and review of the literature.

This study aimed to investigate the clinicopathological characteristics, differential diagnosis and prognosis of pulmonary epithelioid hemangioendothelioma (PEH). PEH is a rare low-grade malignant vascular tumor. The cause of PEH remains unclear. Patient prognosis is unpredictable, with life expectancy ranging from 1 to 15 years due to the fact that estrogenic receptors behave inconsistently within the tumor and the occurence of the disease in male patients does not support the usual hormonal hypothesis. The clinical manifestations, imaging findings, histopathological characteristics and immunohistochemical phenotypes of four cases of epithelioid hemangioendothelioma occurring in the lung were retrospectively analyzed, and a review of the associated literature was conducted. The age of onset for the four PEH cases was 25–54 years, and the disease manifested as multiple nodules in the lungs or pleura. All of the patients underwent lobectomy or pulmonary wedge resection. The morphology of the tumor cells was epithelioid or spindle-shaped with abundant eosinophilic cytoplasm in which lumina or vacuoles containing erythrocytes were observed. The cells were arranged in nests and cords with degenerated interstitial mucoid. The morphology of the majority of the tumor cells was moderate, including mild atypia and little mitosis or necrosis. Immunohistochemical staining showed positive results for CD31, CD34 and F8. PEH is a rare low- to moderate-level tumor occurring in the lungs with differentiation toward vascular endothelial cells. Clinically, it is difficult to distinguish from a variety of other benign and malignant lung diseases. For diagnosis, a distinction must be made from other diseases such as chronic granulomatous disease, amyloid nodules, hamartoma, primary and metastatic lung cancers, malignant mesothelioma and vascular sarcoma. In the present study, the clinicopathological features of four cases of PEH were investigated and the associated literature was reviewed. The results of this study may improve understanding with regards to the diagnosis and therapeutic options for patients with PEH.

Gingival Metastasis as First Sign of Multiorgan Dissemination of Epithelioid Malignant Mesothelioma

Metastatic malignant mesothelioma to the oral cavity is extremely rare. They are more common in the jaw bones than the soft tissue. Occurrence of the malignant disease typically carries an average survival rate of 9-12 months : Thirteen patients underwent neoadjuvant chemotherapy and radical pleurectomy decortication, followed by radiotherapy from August 2012 to September 2013. Patients were followed up with computed tomography of the chest and the abdomen every 3 months. All patients were followed up until February 2014. In January 2014, 11 patients were still alive with a median survival of 11 months, eight patients developed a recurrence and two patients died at 8 and 9 months after surgery. After 1 year from macroscopic radical pleurectomy decortication, a 68-year-old man suffered from gingival mass turned out to be a metastatic deposit of biphasic malignant mesothelioma as first sign of multiorgan recurrence. The patient underwent chemotherapy and local radiotherapy in the oral cavity. This case points out the relevance of biopsy to all new growing lesions, even in uncommon anatomical sites, whenever a history of mesothelioma is on record.

A phase I/II study of azacitidine in combination with temozolomide in patients with unresectable or metastatic soft tissue sarcoma or malignant mesothelioma.

10560 Background: Soft tissue sarcomas are rare tumors, for which complete surgical resection offers the best chance of survival. However, two thirds of diagnosed tumors are unresectable and/or met...

Diagnostic and prognostic value of soluble syndecan-1 in pleural malignancies.

Background. The distinction between malignant and benign pleural effusions is a diagnostic challenge today and measuring soluble biomarkers could add to the diagnostic accuracy. Syndecan-1 is a proteoglycan involved in various cellular functions and is cleaved from the cell surface in a regulated manner. The shed fragment, which can be recovered in effusion supernatant and in serum, retains its binding capacities, but often with different functions and signalling properties than the cell-bound form. Aim. This study aimed to investigate the diagnostic and prognostic value of soluble syndecan-1 in pleural effusions and sera from patients with pleural malignancies. Study Design. Using two cohorts of patients, we assessed the diagnostic and prognostic value of soluble syndecan-1 in pleural effusions and sera, using enzyme-linked immunosorbent assays. Results. In pleural effusions, syndecan-1 distinguished malignant and benign diseases, with an odds ratio of 8.59 (95% CI 3.67 to 20.09). Furthermore, syndecan-1 in pleural effusions predicted a survival difference for patients with pleural metastatic disease and malignant mesothelioma of 11.2 and 9.2 months, respectively. However, no such effects were seen when syndecan-1 was measured in serum. Conclusion. Soluble syndecan-1 is a promising candidate biomarker for the cytopathological diagnosis and prognostication of malignant pleural effusions.

Primary Pleural Malignant Mesothelioma with Delayed Metastasis to the Piriform Sinus: Report of a Case

Piriform sinus tumors are uncommon and silent lesions. Their prognosis is poor because these tumors are usually not detected until they have reached an advanced stage. Almost all piriform sinus cancers are primary squamous cell carcinomas; other primary and metastatic tumors of the hypopharynx are exceedingly rare. One of the rare tumors in the laryngopharyngeal area is sarcomatoid carcinoma, which is an unusual type of squamous cell carcinoma. Another uncommon malignant tumor that is histologically similar to sarcomatoid carcinoma is malignant mesothelioma, which is a rare form of lung carcinoma. The macroscopic appearance and histologic characteristics of sarcomatoid carcinoma and malignant mesothelioma are so similar that differentiation is usually achieved by immunohistochemical examination. To the best of our knowledge, no case of primary or metastatic laryngohypopharyngeal malignant mesothelioma has been previously reported in the literature. In this article, we describe a case of isolated malignant mesothelioma of the piriform sinus that resembled a sarcomatoid carcinoma in a 50-year-old man with a history of lung mesothelioma.

Metastasis of Pleural Mesothelioma Presenting as Bleeding Colonic Polyp

We report the case of a 72-year-old woman with metastatic malignant mesothelioma presenting as right colonic polyp. She was diagnosed with malignant pleural mesothelioma 2 years previously and underwent surgery, radiotherapy, and chemotherapy. After 2 years with a negative follow-up, she was admitted to the infectious disease department for malaria and severe anaemia. A computed tomographic scan and a colonoscopy showed a huge bleeding polypoid lesion in the right colon diagnosed as adenocarcinoma. She underwent a right hemicolectomy; a pathologic examination found neoplastic cell population positive to anti-cytokeratin7, anti-calretinin, anti-vimentin, and negative for anti-cytokeratin 20, MOC-31, and thyroid transcription factor 1, providing a diagnosis of metastatic mesothelioma.

Diagnostic usefulness of EMA, IMP3, and GLUT‐1 for the immunocytochemical distinction of malignant cells from reactive mesothelial cells in effusion cytology using cytospin preparations

To differentiate reactive mesothelial cells (RMs) from metastatic carcinoma and malignant mesothelioma (MM) in effusion cytology is crucial for the cytologic diagnosis and the management of the patients. In the present study, the immunocytochemical staining profile of the epithelial membrane antigen (EMA), the insulin-like growth factor-II mRNA-binding protein 3 (IMP3), and the glucose transporter-1 (GLUT-1) was examined to distinguish RMs from malignant cells. A total of 171 pleural (n = 87) and peritoneal (n = 84) effusion specimens, including 50 benign effusions with RMs, 11 MM effusions, and 110 metastatic malignant effusions, were evaluated for immunocytochemistry. EMA, IMP3, monoclonal GLUT-1, and polyclonal GLUT-1 immunoreactivity were observed in 26.0%, 6.0%, 20.0%, and 18.0% of RMs, respectively. In contrast to RMs, the immunoreactivity in MM was 100%, 36.4%, 100%, and 90.9%; adenocarcinoma (AC) was 100%, 80.8%, 81.7%, and 72.1%; squamous-cell carcinoma was 83.3%, 83.3%, 83.3%, and 66.7%. EMA, IMP3, mGLUT-1, and pGLUT-1 expressions were observed in 98.4%, 65.6%, 88.5%, and 75.4% in the pleural effusion with malignant cells, and 100%, 88.3%, 78.3%, and 71.7% in ascites containing malignant cells, respectively. The findings of the present study indicate that the immunocytochemical staining for EMA, IMP3, and GLUT-1 is a useful diagnostic tool for distinguishing effusions containing malignant cells from those that contain benign cells, and in particular, we suggest that the combination of mGLUT-1 and EMA, and IMP3 and EMA are extremely useful in pleural effusion and in ascites, respectively.