Lymphohistiocytoid Mesothelioma An Often Misdiagnosed Variant of Sarcomatoid Malignant Mesothelioma

Transcription

1 Anatomic Pathology / LYMPHOHISTIOCYTOID MESOTHELIOMA Lymphohistiocytoid Mesothelioma An Often Misdiagnosed Variant of Sarcomatoid Malignant Mesothelioma Hasan S. Khalidi, MD, 1 L. Jeffrey Medeiros, MD, 2 and Hector Battifora, MD 3 Key Words: Lymphohistiocytoid mesothelioma; Sarcomatoid mesothelioma; Malignant lymphoma; Immunohistochemistry Abstract Three cases of lymphohistiocytoid mesothelioma, a rare variant of pleural sarcomatoid malignant mesothelioma, are described. Histologically, the neoplasms were characterized by a diffuse discohesive proliferation of atypical histiocytoid cells intermixed with a marked lymphocytic and lesser plasmacytic infiltrate. One case initially was misdiagnosed as a ganglioneuroma, a second case was misinterpreted as malignant lymphoma, and a third case was sent in consultation with the differential diagnosis of inflammatory pseudotumor vs mesothelioma. Immunohistochemical studies showed strong and generalized expression of cytokeratins and vimentin by the neoplastic histiocytoid cells in all 3 cases. Two cases were positive for calretinin, one of which also was positive for HBME-1, thrombomodulin, and LeuM1. None of the cases stained with the epithelial glycoprotein markers carcinoembryonic antigen, B72.3, and Ber-EP4, or the blood group antigen, BG-8. The immunophenotype of the lymphoplasmacytic infiltrate revealed predominantly reactive, mature T cells, with fewer polytypic plasma cells, histiocytes, and B cells. In lymphohistiocytoid mesothelioma, as in the usual examples of sarcomatoid mesothelioma, the demonstration of cytokeratin expression by the neoplastic cells is the most useful diagnostic finding that allows exclusion of other neoplasms with which this entity may be confused. Lymphohistiocytoid mesothelioma (LHM) is an infrequent variant of sarcomatoid mesothelioma, first described by Henderson and colleagues in They described 3 patients with pleural-based neoplasms, 2 of which initially were misinterpreted histologically as non-hodgkin lymphoma. The tumors showed a diffuse proliferation of large, atypical, ovoid to spindle histiocytoid cells admixed with numerous lymphocytes and plasma cells, and 1 case had many eosinophils. The differential diagnosis for these neoplasms, in addition to non- Hodgkin lymphoma, included Hodgkin disease, carcinoma, sarcoma, and a reactive mesothelial process. Ultrastructural and immunohistochemical stains were considered mandatory to establish the correct diagnosis. Because LHM continues to be misdiagnosed, most often as malignant lymphoma, we report 3 additional cases from our consultation files, emphasizing the diagnostic role of immunohistochemical studies. Materials and Methods Three cases of LHM were culled from a series of 612 malignant mesotheliomas in the consultation files of one of us (H.B.). Formalin-fixed paraffin-embedded tumor tissue blocks were available for all cases. Immunohistochemical studies were performed using fixed paraffin-embedded tissue sections with a panel of commercially available antibodies. The sources and dilutions of the primary antibodies and the pretreatment methods used are given in Table 1. Heat-induced epitope retrieval was performed where indicated using previously published methods. 2 Appropriate positive controls were run concurrently for all antibodies tested. All immunostains American Society of Clinical Pathologists Am J Clin Pathol 2000;113:

2 Khalidi et al / LYMPHOHISTIOCYTOID MESOTHELIOMA Table 1 Antibodies, Sources, Dilutions, and Pretreatment Methods Antigen Antibody (Clone) Type Dilution Treatment Source Keratin AE1, AE3, CAM 5.2, C, M 1:2 Steam HIER Ventana, Tucson, AZ 35bH11 CEA CEJ065 M 1:100 Steam HIER Immunon, Pittsburgh, PA CD15 MMA M 1:20 Steam HIER Becton Dickinson, San Jose, CA B72.3 B72.3 M 1:30 Steam HIER Signet, Dedham, MA Ber-EP4 Ber-EP4 M 1:200 Protease K Dako, Carpinteria, CA BG-8 F3 M 1:75 Steam HIER Signet HBME-1 HBME-1 M 1:10,000 Steam HIER Dako Thrombomodulin 1009 M 1:25 Dako Calretinin P 1:25 Steam HIER Zymed, San Francisco CA Vimentin V9 M 1:100 Steam HIER Dako CD3 P 1:100 Steam HIER Dako CD5 4C7 M 1:10 MW + citrate Novocastra, Newcastle upon Tyne, England CD20 L26 M 1:100 Steam HIER Dako CD30 Ber-H2 M 1:15 Steam HIER Dako CD43 Leu-22 M 1:20 Steam HIER Dako CD45/45RB PD7/26 and 2B11 C, M 1:200 Steam HIER Dako TdT M 1:10 Steam HIE R Supertechs, Bethesda, MD CD68 KP1 M 1:1,000 Steam HIER Dako Kappa P 1:3,000 MW + citrate Dako Lambda P 1:3,000 MW + citrate Dako p53 DO7 M 1:150 Steam HIER Novocastra C, cocktail; CEA, carcinoembryonic antigen; HIER, heat-induced epitope retrieval; M, monoclonal; MW + citrate, microwave HIER with a 0.01-mol/L concentration of citric acid for 22 minutes; P, polyclonal; Protease K, Protease K enzyme for 5 minutes at 37 C; TdT, terminal deoxynucleotidyl transferase. were performed using an automated immunostainer (Ventana/BioTek 1000, Tucson, AZ). Results Case Reports The clinical information, radiologic findings, and referral diagnosis for the 3 patients are summarized in Table 2. The patients ages were 60, 74, and 67 years. Clinical symptoms included chest pain, productive cough, and fatigue. Chest radiograph and computed tomography findings, available for cases 2 and 3, showed pleural-based nodules, pleural thickening, and effusion. By history, unspecified radiologic studies for case 1 also showed a pleural-based mass involving the mediastinum and chest wall. In none of the patients could a history of asbestos exposure be established. The patients were alive after 6 years (case 1), 10 months (case 2), and 3 months (case 3) after initial diagnosis. In each case, the correct diagnosis was difficult to establish. In case 1, the neoplasm originally was diagnosed as a ganglioneuroma, and the neoplasm initially responded to radiotherapy. In case 2, the referring pathologist s differential diagnosis included reactive mesothelial hyperplasia and malignant mesothelioma. In case 3, the neoplasm initially was diagnosed as non-hodgkin lymphoma. Microscopic Features The 3 neoplasms had similar histologic findings. The tumors consisted of relatively well-circumscribed pleuralbased nodules composed of a diffuse proliferation of large discohesive cells with a histiocytoid appearance, although atypical spindle cells also were noted Image 1 and Image 2. The neoplastic cells were ovoid with vesicular nuclear chromatin, round prominent nucleoli, and a variable amount of pale acidophilic cytoplasm. Case 1, initially diagnosed as ganglioneuroma, contained plump tumor cells with some cytologic features reminiscent of ganglion cells Image 3. A focus of solid epithelial type malignant mesothelioma was present in case 2. Rare cells resembling mononuclear Reed-Sternberg cells also were found. Mitotic activity was mild to moderate. Focal necrosis was seen in 1 case. A dense infiltrate of small lymphocytes, plasmacytoid lymphocytes, and mature plasma cells was admixed with the spindle cells in each case. In 1 neoplasm, the plasma cell 650 Am J Clin Pathol 2000;113: American Society of Clinical Pathologists

3 Anatomic Pathology / ORIGINAL ARTICLE Table 2 Clinical Data Case No./ Sex/Age (y) Clinical Findings Radiologic Findings Referral Diagnosis 1/M/60 First examined in 1991 because Not available Ganglioneuroma of a mass involving chest wall and posterior mediastinum; treated with local radiotherapy; recurrence of mass in 1996; asbestos history, negative 2/F/74 10-mo history of progressive left CXR, left paraspinous lesions with pleural Reactive mesothelial rib pain; asbestos history, unknown effusion and thickening; CT, pleural-based hyperplasia vs mass posterior to aorta mesothelioma 3/M/67 5-wk history of pain in right shoulder CXR, multiloculated right pleural mass; CT, Malignant lymphoma and lateral chest and intermittent cough; asbestos history, negative CT, computerized tomography scan; CXR, chest radiograph. extensive pleural thickening and nodularity in the right hemithorax, especially in apex, with extension to paravertebral area; bilateral pleural plaques and calcifications present, typical of asbestosis Image 1 (Case 3) Lymphohistiocytoid mesothelioma. Numerous small reactive lymphocytes with occasional eosinophils and plasma cells are admixed with ovoid and spindle-shaped neoplastic cells in this field. This case was sent in consultation with the differential diagnosis of inflammatory pseudotumor vs mesothelioma (H&E, 200). Image 2 (Case 2) Lymphohistiocytoid mesothelioma. In this case, numerous small reactive lymphocytes were present as nodules (right center) and diffusely scattered throughout the neoplasm. Occasional eosinophils also were scattered throughout the neoplasm. This case, sent in consultation, initially was misclassified as malignant lymphoma (H&E, 100). infiltrate was marked. Occasional eosinophils were scattered throughout all 3 tumors. A variable degree of perivascular fibrosis also was noted. Occasionally, aggregates of reactive epithelial mesothelial cells were present at the edge of the specimens. Immunohistochemical Findings The immunohistochemical results are given in Table 3 and summarized briefly here. The neoplastic cells in every case were diffusely positive for cytokeratin, with strong cytoplasmic staining and perinuclear accentuation Image 4. Vimentin was strongly positive in 2 tumors (cases 2 and 3). Two neoplasms (cases 1 and 3) were positive for calretinin, with a nuclear and cytoplasmic pattern of staining Image 5. Case 1 also was positive for thrombomodulin, HBME-1 Image 6, and CD15. The antip53 antibody was positive in 10% and 70% of the neoplastic cells in cases 1 and 3, respectively. There was no p53 American Society of Clinical Pathologists Am J Clin Pathol 2000;113:

4 Khalidi et al / LYMPHOHISTIOCYTOID MESOTHELIOMA Image 3 (Case 1) Lymphohistiocytoid mesothelioma. The ovoid neoplastic cells with abundant cytoplasm in this field represented a minority of all cells in this tumor. The majority of cells were small reactive lymphocytes. This case was misinterpreted originally as ganglioneuroma 5 years before the correct diagnosis was established (H&E, 200). Image 4 (Case 1) The neoplastic cells were strongly positive for cytokeratin (immunoperoxidase with hematoxylin counterstain, 200). Table 3 Immunohistochemical Results of Neoplastic Cells for 3 Cases Case No No. of Reactive Cases Cytokeratin Calretinin + * + * 2 Vimentin p53 + (10%) + (70%) 2 CD HBME Thrombomodulin + 1 Carcinoembryonic antigen 0 Ber-EP4 0 B BG-8 0 Leukocyte markers (CD3, CD5, 0 CD20, CD30, CD43, CD45/45RB, CD68, TdT, immunoglobulin kappa, and immunoglobulin lambda) +, positive;, negative. * Nuclear and cytoplasmic staining. Focal staining Membranous staining. immunostaining of case 2. All neoplasms were negative for carcinoembryonic antigen, B72.3, Ber-EP4, and BG-8. The neoplastic cells also were negative for the leukocyte-associated markers CD3, CD5, CD20, CD43, CD45/45RB, CD68, terminal deoxynucleotidyl transferase (TdT), and immunoglobulin light chains. Most of the reactive lymphocytes, all CD45/45RB+, were mature T cells positive for CD3 Image 7, CD5, and CD43 and negative for TdT. Scattered CD20+ B cells also were present. The plasma cells expressed polytypic immunoglobulin kappa and lambda light chains. Discussion LHM is a rare variant of sarcomatoid malignant mesothelioma. Only 3 cases have been reported in the literature, in a single study from Australia. 1 These 3 cases represented 0.8% 652 Am J Clin Pathol 2000;113: American Society of Clinical Pathologists

5 Anatomic Pathology / ORIGINAL ARTICLE Image 5 (Case 1) The neoplastic cells were strongly positive for calretinin (immunoperoxidase with hematoxylin counterstain, 200). Image 6 (Case 1) The neoplastic cells reacted with the HBME-1 antibody, with a membranous and cytoplasmic pattern of staining (immunoperoxidase with hematoxylin counterstain, 200). Image 7 (Case 1) Numerous small reactive lymphocytes admixed within this neoplasm were predominantly T cells, positive for CD3 (shown) and other T-cell antigens (not shown). A few scattered CD20+ B cells (not shown) also were present (H&E, 200). of mesothelioma cases entered in the Australian Mesothelioma Surveillance Program. The 3 cases we report herein represent almost 0.5% of our total series of malignant mesothelioma cases. However, if only sarcomatoid variants are considered (107 cases), the incidence of LHM approaches 3%. The 3 LHM cases we report were pleural-based, occurring in patients older than 55 years. One case (case 1) manifested as a localized mass that recurred after 5 years, indicating indolent clinical behavior. All 3 patients are still alive; however, the clinical behavior of the LHMs in cases 2 and 3 cannot be assessed reliably owing to relatively short clinical follow-up. No history of asbestos exposure could be established clearly in our series. These findings differ somewhat from the 3 Australian cases of LHM reported by Henderson and colleagues. 1 The previously reported LHM cases had typical clinical, radiologic, and macroscopic findings of diffuse malignant mesothelioma, and all patients died within months after an aggressive clinical course. Histologically, LHM is a variant of sarcomatoid malignant mesothelioma, characterized by a diffuse proliferation of large, ovoid histiocyte-like and spindle cells, uniformly intermixed with a prominent lymphocytic or lymphoplasmacytic infiltrate. All 3 Australian cases and 1 of our cases initially were misinterpreted as non-hodgkin lymphoma. The large histiocytoid neoplastic cells may morphologically mimic the cells of large noncleaved cell or anaplastic (Ki-1 positive) large cell lymphoma. Cases of LHM with scattered neoplastic cells in a mixed inflammatory cell background also may resemble Hodgkin disease. In addition, inflammatory pseudotumor and various sarcomas with a prominent inflammatory infiltrate may enter the differential diagnosis with LHM. Immunohistochemical demonstration that the neoplastic cells express cytokeratin will exclude all of these possibilities from the differential diagnosis and, in the proper clinical context, establish the diagnosis of LHM. More problematic is the distinction of LHM from sarcomatoid carcinoma of the lung involving the pleural American Society of Clinical Pathologists Am J Clin Pathol 2000;113:

6 Khalidi et al / LYMPHOHISTIOCYTOID MESOTHELIOMA surface, as cytokeratin expression by the neoplastic cells will occur in both entities. However, in sarcomatoid carcinoma, a dominant intrapulmonary tumor mass should be evident. Rarely, thymoma may involve the pleura and manifest with a clinical and radiologic appearance that can closely mimic mesothelioma. 3-5 The consistent expression of cytokeratin by the epithelial component of thymomas and thymic carcinomas may lead to diagnostic difficulties with LHM in such cases. However, many of the accompanying lymphocytes in most thymomas express immature T- cell markers, such as TdT and CD1a. 6-8 These markers can be particularly helpful in the identification of thymoma at unusual sites. 8 In addition, the neoplastic cells of thymic carcinomas have been reported to immunoreact with CD5. 9 The reactive lymphoid cells accompanying the neoplastic cells in the 3 LHM cases we report were negative for TdT, and the neoplastic cells were negative for CD5. The neoplastic cells of LHM do not react with epithelial markers that are used to distinguish epithelial mesothelioma from adenocarcinoma. As is the case for sarcomatoid mesothelioma, these immunostains do not contribute substantially to the diagnosis of LHM. Assessment for cytokeratin is the single most important immunohistochemical study The expression of calretinin (cases 1 and 3), thrombomodulin (case 1), and HBME-1 (case 1) by the neoplastic cells in 2 of our cases of LHM indicates that these mesothelial markers can be helpful for bolstering the diagnosis of LHM in some cases. The LHM tumor cells did not stain with the leukocyteassociated markers CD3, CD5, CD20, CD30, CD43, CD45/45RB, CD68, TdT, and immunoglobulin light chains. The inflammatory background consists predominantly of mature reactive T cells, with scattered B cells and polytypic plasma cells. In the presence of strong and generalized staining of the histiocytoid and spindle cells for cytokeratin, however, these leukocyte markers are not considered necessary. However, the immature thymocyte marker, TdT, as mentioned previously, may be helpful to rule out thymoma involving the pleural surface. 7 Despite its rarity, LHM always should be considered in the differential diagnosis of any pleural-based lesion associated with an inflammatory background. In addition, caution must be exercised, particularly in dealing with small biopsy specimens, not to confuse reactive submesothelial spindle cells with neoplastic cells. 10,11 Cytologic atypia, invasiveness, and an irregular growth pattern, as occur in sarcomatoid mesothelioma in general, are useful for distinguishing LHM from mesothelial hyperplasia. Address reprint requests to Dr Medeiros: Dept of Pathology, Box 85, U.T.M.D. Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX References 1. Henderson DW, Attwood HD, Constance TJ, et al. Lymphohistiocytoid mesothelioma: a rare lymphomatoid variant of predominantly sarcomatoid mesothelioma. Ultrastruct Pathol. 1988;12: Gown AM, De Wever N, Battifora H. Microwave-based antigenic unmasking: a revolutionary new technique for routine immunohistochemistry. Appl Immunohistochemistry. 1993;1: Fushimi H, Tanio Y, Kotoh K. Ectopic thymoma mimicking diffuse pleural mesothelioma: a case report. Hum Pathol. 1998;29: Hofmann W, Moller P, Manke HG, et al. Thymoma: a clinicopathologic study of 98 cases with special reference to three unusual cases. Pathol Res Pract. 1985;179: Payne CB, Morningstar WA, Chester EH. Thymoma of the pleura masquerading as diffuse mesothelioma. Am Rev Respir Dis. 1966;94: Chilosi M, Menestrina F, Iannucci A, et al. Immunohistochemical analysis of thymoma. Am J Surg Pathol. 1998;8: Fukayama M, Maeda Y, Funata N, et al. Pulmonary and pleural thymoma: diagnostic application of lymphocyte markers to the thymoma of unusual site. Am J Clin Pathol. 1988;89: Mokhtar N, Hsu S-M, Lad RP, et al. Thymoma: lymphoid and epithelial components mirror the phenotype of normal thymus. Hum Pathol. 1984;15: Dorfman DM, Shahsafaei A, Chan JK. Thymic carcinomas, but not thymomas and carcinomas of other sites, show CD5 immunoreactivity. Am J Surg Pathol. 1997;21: Battifora H. The pleura. In: Sternberg SS, ed. Diagnostic Surgical Pathology. 2nd ed. New York, NY: Raven Press; 1994: Battifora H, McCaughey WTE. Tumors of the Serous Membranes. 3rd ed. Third Series, Fascicle 15. Washington DC: Armed Forces Institute of Pathology; 1995: Riera JR, Astengo-Osuna C, Longmate JA, et al. The immunohistochemical diagnostic panel for epithelial mesothelioma: a reevaluation following heat-induced epitope retrieval. Am J Surg Pathol. 1997;21: From the 1 Department of Pathology, Jordan University of Science and Technology, Irbid, Jordan; the 2 Division of Pathology, University of Texas M.D. Anderson Cancer Center, Houston, TX; and 3 Pacific Coast Reference Laboratory, Cypress, CA. 654 Am J Clin Pathol 2000;113: American Society of Clinical Pathologists