The Diagnosis of Malignant Mesothelioma Andrew Churg, MD Department of Pathology University of British Columbia Vancouver, BC, Canada achurg@mail.ubc.ca Notice of Faculty Disclosure In accordance with ACCME guidelines, any individual in a position to influence and/or control the content of this CME activity has disclosed all relevant financial relationships within the past 12 months with commercial interests that provide products and/or services related to the content of this CME activity. The individual below has disclosed the following financial relationship with commercial interest: Andrew Churg, MD, serves as a consultant to various law firms in asbestos litigation Mesothelioma
Pleural Mesothelioma Metastases to Contralateral Lung Peritoneal Mesothelioma Courtesy Dr. D. Henderson Histologic Patterns of Malignant Mesothelioma* Epithelial Sarcomatous Mixed Epithelial and Sarcomatous Also called Biphasic * Classification in Series 4 Fascicle and WHO 2004
Names Not to Be Used for Different Forms of Epithelial Mesothelioma Epithelioid (Sheet-like) Tubulopapillary Microcystic/Adenomatoid Deciduoid Unnamed patterns Every possible mixture of above However, high grade ( = pleomorphic) perhaps should be named Recent reports suggest pleomorphic has a very poor prognosis, similar to sarcomatous (Ordonez Mod Path 2012; Kadota JTO 2011) Names Not to Be Used for Different Forms of Epithelial Mesothelioma Epithelioid (Sheet-like) Tubulopapillary Microcystic/Adenomatoid Deciduoid Unnamed patterns Every possible mixture of above No reproducibility High grade among pathologists Mixtures of types common (problem with small bx) Thus far only 1 claimed correlation with survival (has not been confirmed (Mod Path 2011) MP2290
Histologic Patterns of Malignant Mesothelioma Epithelial Sarcomatous Mixed Epithelial and Sarcomatous Also called Biphasic Good concordance among pathologists This classification correlates with survival Sarcomatous forms do not respond to radical triple therapy Mesothelioma Ca Colon MP1979 Mesothelioma Carcinoma
Epithelial mesothelioma MP2135 Tubulopapillary pattern (Do NOT mention in report!!!) MP1276 vr53 Deciduoid pattern (Do NOT mention in report!!!)
04-6545 Adenomatoid patterns Do not mention in report 42502 MM Epithelial Mesotheliomas
Immunohistochemical Staining Patterns in Carcinoma and Mesothelioa Antibody Mesothelioma Carcinoma Broad spectrum keratin + + Vimentin + + EMA + (membrane) + (cytoplasmic) CEA - + LeuM1 - + B72.3 - + BEREP4 +/- + MOC31 - + HMFG + (membrane) + (cytoplasmic) Lewis blood group antigens (Bg8) - + Thrombomodulin + + Calretinin + - Cytokeratin 5/6 + - HBME1 + (membrane) + WT-1 + - D2-40/Podoplanin + (membrane) - Mesothelin + - Napsin A - + Sensitivity and Specificity of Various Mesothelioma and Carcinoma Markers: Yaziji et al: Modern Pathology 2006 Mesothelioma: Expected staining CK5/6 Calretinin CEA 99-15067-1
CK5/6 Referred in case: Mesothelioma- Aberrant Staining for CD15 WT-1 Calretinin CD15 MP1931 Referred in case: Aberrant Staining for MOC-31 Calretinin WT-1 D2-40 CK5/6 MOC-31 MP2236 Which Antibodies Should You Use? If unsure whether mesothelioma or carcinoma select 2 mesothelioma markers and 2 carcinoma markers Modify your markers to account for likely primary site If pretty sure you are dealing with one or the other, 3 of one and 1 of the other might be another choice You need to know how these markers behave in your lab! The more markers you use, the more anomalous results you can expect! Remember that most sarcomatous mesotheliomas only stain with pan-keratin
Recommended Antibodies for Separating Mesothelioma from Adenocarcinoma (From Ordonez 2007; Churg 2006) Mesothelioma Markers Calretinin Cytokeratin 5/6 1 WT-1 2 D2-40 2 1 Positive in many squamous carcinomas Carcinoma Markers CEA 3 B72.3 LeuM1 MOC-31 TTF-1 4 p63 (for squamous ca) 3 Positive in <50% of serous carcinomas 4 Stains 75% of lung adenocarcinomas Dealing with Morphologically High Grade Epithelial Tumors? Mesothelioma There are several hundred thousand malignant pleural effusions/yr in the US There are 2500 mesotheliomas (and not all are pleural) The odds are overwhelming that a high grade epithelial tumor that stains only with keratin is a carcinoma and not a mesothelioma The diagnosis of pleomorphic mesothelioma requires exactly correct IHC Pleomorphic Epithelial Mesothelioma Calretinin WT-1 MOC-31
Cautions Re Diagnosing Epithelial Mesotheliomas Value of names is for pathologic recognition Morphologic subtypes (apart from pleomorphic) have no clear prognostic significance--differentiation is not a concept easily applied to mesotheliomas Avoid use of well-differentiated in diagnosis of malignant mesotheliomas because it causes confusion with well differentiated papillary mesothelioma a generally benign tumor Don t get hung up on IHC results if the morphology fits and the IHC mostly fits High grade epithelial tumors are more likely carcinoma than mesothelioma here IHC critical for diagnosis Subtypes of Sarcomatous Mesothelioma Sarcomatous NOS (like fibrosarcoma or MFH) With heterologous elements Lymphohistiocytoid (probably a form of epithelial mesothelioma)* Transitional Desmoplastic *Galateau-Salle et al: AJSP 2007 Sarcomatous mesothelioma 11-54385
Sarcomatous mesothelioma Pan-Keratin WT-1 Calretinin IHC in Sarcomatous Mesos 93% Keratin + (Klebe Mod Path 2010) 31% Calretinin + ( ) 30% WT-1 + 84% Podoplanin +?(Padgett AJSP 2008) LS04-1326 Mesothelioma with heterologous differentiation Keratin (V. Roggli)
Lymphohistiocytoid Mesothelioma Keratin MP1115 Cautions re Diagnosing Sarcomatous Mesotheliomas There is more agreement on nomenclature than is true of epithelial forms Sarcomatous forms less often show mixtures Pleomorphism/cytologic atypia common in sarcomatous mesotheliomas Desmoplastic mesotheliomas are frequently misdiagnosed Most sarcomatous mesotheliomas only show pan-keratin staining (save your money and don t get upset when nothing else stains!) Avoid the term fibrous mesothelioma for sarcomatous forms because the same term has been used for benign solitary fibrous tumors Mixed Epithelial and Sarcomatous Mesothelioma MP1335
Differential Diagnosis: Diffuse Pleural/Peritoneal Tumors Metastatic carcinoma or sarcoma (including direct spread) Primary serous papillary carcinoma Angiosarcoma Synovial sarcoma? Chondrosarcoma & osteosarcoma in pleura (may all be mesotheliomas) Squamous cell ca of lung mimicking mesothelioma R2247 R2247 Squamous cell ca Papillary Serous Carcinoma of Peritoneum 02-16762
Epithelioid hemangioendothelioma MP2069 Keratin CD31 Separation of Benign vs Malignant Mesothelial Prolfierations US-Canadian Mesothelioma Reference Panel Data Total circulated cases 1994-1998 217 Percent of cases with disagreement about benign vs maligant 22% Distribution of Proliferating Mesothelial Cells and Malignancy In a Thickened Pleura Benign or malignant Layering (benign) Thick pleura Usually benign Malignant Fat 1
Mesothelioma: full thickness spread in a thick pleura MP1974 MP1974 Mesothelioma: expansile stromal nodule 00-2067
Mesothelioma 00-2067 MM Stromal Invasion and Mesothelioma Stromal invasion is the most useful single criterion for separating benign from malignant mesothelial proliferations Deciding what is invasion and what is entrapment can be difficult? Invasion MP924
Not Invasion: En Face Cut MP924 Entrapment 36704 Pericardium Linear Array Organizing Pericarditis MP2160
CK7 Limit to Penetration vs Invasion MP1696
MP1696 MP1696 Keratin Benign reaction Sharp circumscription Limit to penetration MP1696
Mesothelioma: Keratin MP584 Peritoneal MM Keratin Separating Invasion from Entrapment Be cautious diagnosing invasion in the presence of a major inflammatory reaction Linear arrays tend to be entrapped Sharply circumscribed mesothelial proliferations tend to be entrapped En face cuts are a major problem in small biopsies If in doubt it s better to report the process as atypical mesothelial hyperplasia Warning Data-Free Zone Ahead Courtesy Dr. S. Schnitt
The Concept of Mesothelioma in Situ D Whitaker, DW Henderson, KB Shilkin Sem Diag Pathol 1992; 9: 151-161 Seven cases All had areas of invasive mesothelioma In situ mesothelioma = single layer of surface cells 1?Mesothelioma in Situ? 2 3 4 Reaction to Pneumothorax Presumed MIS + Mesothelioma 1 2 MP1342 MP896
3 Presumed Mesothelioma in Situ + Mesothelioma 4 MP1497 PHR10-1391 1?Mesothelioma in Situ? 2 3 4 Recommendation: The best time to diagnose mesothelioma in situ is never
Criteria for the Diagnosis of Desmoplastic Mesothelioma Bulk of lesion is paucicellular and shows a storiform or patternless pattern plus Stromal invasion or Bland necrosis or Overtly sarcomatous foci or Nodular stromal expansions or Distant metastases Desmoplastic mesothelioma MP2091 Desmoplastic mesothelioma: patternless pattern of Stout + ropey collagen MP2091
Desmoplastic mesothelioma MP2091 Desmoplastic mesothelioma: downward invasion of fat MP2091 Keratin MP2091
Desmoplastic mesothelioma: invasion of fat 93-8663 Keratin Invasion of fat 93-8663 DMM Sarcomatous Focus MP2187
Bland Necrosis MP 1058 Bland Necrosis 93-8663 Thin desmoplastic mesothelioma: nodular stromal expansion MP2230
Thin desmoplastic mesothelioma: nodular stromal expansion Thin desmoplastic mesothelioma: nodular stromal expansion Features of Organizing Pleuritis * Cellularity greatest immediately under effusion Progressively fibrotic and paucicellular away from effusion ( zonation ) Capillaries perpendicular to surface Cells immediately under effusion can be very atypical, particularly when mesothelial cells are mixed with fibrin Examine areas away from fibrin All active mesothelial proliferations are keratin + Fibrosis can extend into fat (but usually keratin negative)! * Also called fibrosing pleurisy, organizing pleurisy
Organizing pleuritis MP918 OP MP918 OP Organizing pleuritis MP1045
Organizing pleuritis MP1045 Organizing pleuritis (organizing empyema) VS09-33769 Organizing pleuritis (organizing empyema) VS09-33769
Pan-keratin: sharply demarcated line of positivity no keratin positive cells in fat Pan-keratin (hydrocoele): lamellar arrays MP1147
Churg and Galateau-Salle Arch Path 2012 MP1181 OP p53 MP1181
98-14771 EMA 98-14771 Sensitivity and Specificity of Immunohistochemical Marks in Separating Benign and Malignant Mesothelial Proliferations (King et al Histopathology 2006) Authors conclusions: Immunohistochemistry is of limited value The diagnostic importance of histological features seen on plain tissue sections is emphasized
Desmin <10% Desmin >10% EMA <10% EMA >10% p53 <10% p53 >10% Survival at 5 Years by IHC Stain Result (Cutoff 10% Staining) (Churg and Galateau-Salle, Arch Path 2012) Survival at 5 Years Using a 10% Staining Cutoff 90 80 Desmin EMA p53 70 % Surviving 60 50 40 30 20 10 0 16 Conclusions Re IHC for Separating Benign from Malignant Mesothelial Proliferations Pan-keratin is very useful because it tells you where the proliferating cells are located (but all proliferating mesothelial cells are pan-keratin positive) Other markers may work in a statistical sense but aren t suitable for an individual case Combinations of markers might be a potential approach, but require exacting control of IHC
Benign Reaction Mesothelioma Chromosome 9 centromere-- green p16 probe--red 21 M with pleural effusion, pleural thickening. Clinically suspicious for malignancy. Biopsy shows only surface proliferation MP2243
p16 FISH: essentially 100% homozygous deletion (courtesy Dr Harry Hwang) Problems with p16 FISH for Diagnosing Mesothelioma vs Reactive Proliferation Preparation technically time consuming/difficult Interpretation of homozygous deletion in tissue section can be a problem Works well if groups of cells present, but difficult if lines of cells are the only finding Cutoff value needed because in tissue section some fraction of cells tend always appear to have homozygous deletion FISH homozygous deletions often don t correlate with protein staining by IHC NB: 30% of pleural mesotheliomas and 25-50% of peritoneal mesotheliomas do not show homozygous p16 deletion
Suitable Specimens for Diagnosing Mesothelioma Needle biopsy Low yield (literature values about 25%) Rarely useful for desmoplastic mesothelioma Thoracscopic biopsy High yield (literature values about >90%) Open biopsy/pleural stripping High yield May be particularly useful for desmoplastic mesothelioma Cytology Low yield (literature values about 25%) Often hard to tell reactive from malignant mesothelial cells When definitely malignant, often hard to separate carcinoma from mesothelioma (IH results may be strange in cell blocks) Survival in Pleural Mesothelioma by Histologic Type (Flores: J Thoracic Oncol 2007) Epi Mixed Sarc Survival in Pleural Mesothelioma by Treatment (Flores: J Thoracic Oncol 2007) Multimodality Therapy Surgery Alone
Survival in Peritoneal Mesothelioma after Debulking and Hot Intraperitoneal Chemotherapy (Cao: J Oncol 2012) Female N=135 Male N=159 Survival in Peritoneal Mesothelioma after Debulking and Hot Intraperitoneal Chemotherapy (Cao: J Oncol 2012) Female N=135 It s probably a good idea to include a comment in your report indicating that with proper therapy survival in peritoneal mesothelioma is 50% or better and provide a reference Male N=159 Don t confuse epidemiology with diagnosis