Timothy Craig Allen

Guidelines for pathologic diagnosis of Malignant Mesothelioma: 2017 Update of the consensus statement from the International Mesothelioma Interest Group

CONTEXTn- Malignant mesothelioma (MM) is an uncommon tumor that can be difficult to diagnose.nnnOBJECTIVEn- To provide updated, practical guidelines for the pathologic diagnosis of MM.nnnDATA SOURCESn- Pathologists involved in the International Mesothelioma Interest Group and others with an interest and expertise in the field contributed to this update. Reference material included up-to-date, peer-reviewed publications and textbooks.nnnCONCLUSIONSn- There was discussion and consensus opinion regarding guidelines for (1) distinguishing benign from malignant mesothelial proliferations (both epithelioid and spindle cell lesions), (2) cytologic diagnosis of MM, (3) recognition of the key histologic features of pleural and peritoneal MM, (4) use of histochemical and immunohistochemical stains in the diagnosis and differential diagnosis of MM, (5) differentiating epithelioid MM from various carcinomas (lung, breast, ovarian, and colonic adenocarcinomas, and squamous cell and renal cell carcinomas), (6) diagnosis of sarcomatoid MM, (7) use of molecular markers in the diagnosis of MM, (8) electron microscopy in the diagnosis of MM, and (9) some caveats and pitfalls in the diagnosis of MM. Immunohistochemical panels are integral to the diagnosis of MM, but the exact makeup of panels employed is dependent on the differential diagnosis and on the antibodies available in a given laboratory. Depending on the morphology, immunohistochemical panels should contain both positive and negative markers for mesothelial differentiation and for lesions considered in the differential diagnosis. Immunohistochemical markers should have either sensitivity or specificity greater than 80% for the lesions in question. Interpretation of positivity generally should take into account the localization of the stain (eg, nuclear versus cytoplasmic) and the percentage of cells staining (>10% is suggested for cytoplasmic and membranous markers). Selected molecular markers are now being used to distinguish benign from malignant mesothelial proliferations. These guidelines are meant to be a practical diagnostic reference for the pathologist; however, some new pathologic predictors of prognosis and response to therapy are also included.

Programmed Death Ligand-1 Immunohistochemistry— A New Challenge for Pathologists: A Perspective From Members of the Pulmonary Pathology Society

The binding of programmed death ligand-1 and ligand-2 (PD-L1 and PD-L2) to PD-1 blocks T-cell-mediated immune response to tumor. Antibodies that target programmed death receptor-1 (PD-1) will block the ligand-receptor interface, thereby allowing T cells to attack the tumor and increase antitumor immune response. In clinical trials, PD-1 inhibitors have been associated with an approximately 20% overall response rate in unselected patients with non-small cell lung cancer, with sustained tumor response in a subset of patients treated by these immune checkpoint inhibitors. Facing a proliferation of PD-L1 immunohistochemistry clones, staining platforms, and scoring criteria, the pathologist must decide on the feasibility of introducing a newly approved companion diagnostic assay that may require purchase not only of a specific antibody kit but of a particular staining platform. Given the likely reality that clinical practice may, in the near future, demand access to 4 different PD-L1 antibodies coupled with different immunohistochemistry platforms, laboratories will be challenged with deciding among this variety of testing methods, each with its own potential benefits. Another immediate challenge to PD-L1 testing in lung cancer patients is that of access to adequate tumor tissue, given that non-small cell lung cancer samples are often extremely limited in size. With PD-L1 testing it has become clear that the historically used US regulatory approach of one assay-one drug will not be sustainable. One evolving concept is that of complementary diagnostics, a novel regulatory pathway initiated by the US Food and Drug Administration, which is distinct from companion diagnostics in that it may present additional flexibility. Although pathologists need to face the practical reality that oncologists will be asking regularly for the PD-L1 immunohistochemistry status of their patients tumors, we should also keep in mind that there may be room for improvement of biomarkers for immunotherapy response. The field is rich with opportunities for investigation into biomarkers of immunotherapy response, particularly in the form of collaborative, multidisciplinary studies that incorporate oncologists, pathologists, and basic scientists. Pathologists must take the lead in the rational incorporation of these biomarkers into clinical practice.

Acute lung injury: A clinical and molecular review

CONTEXTnAcute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are a continuum of lung changes arising from a wide variety of lung injuries, frequently resulting in significant morbidity and frequently in death. Research regarding the molecular pathophysiology of ALI/ARDS is ongoing, with the aim toward developing prognostic molecular biomarkers and molecular-based therapy.nnnOBJECTIVEnTo review the clinical, radiologic, and pathologic features of ALI/ARDS; and the molecular pathophysiology of ALI/ARDS, with consideration of possible predictive/prognostic molecular biomarkers and possible molecular-based therapies.nnnDATA SOURCESnExamination of the English-language medical literature regarding ALI and ARDS.nnnCONCLUSIONSnARDS is primarily a clinicoradiologic diagnosis; however, lung biopsy plays an important diagnostic role in certain cases. A significant amount of progress has been made in the elucidation of ARDS pathophysiology and in predicting patient response, however, currently there is no viable predictive molecular biomarkers for predicting the severity of ARDS, or molecular-based ARDS therapies. The proinflammatory cytokines TNF-α (tumor necrosis factor α), interleukin (IL)-1β, IL-6, IL-8, and IL-18 are among the most promising as biomarkers for predicting morbidity and mortality.

Interleukin 8 and acute lung injury.

Acute lung injury is a complex clinical syndrome involving acute inflammation, microvascular damage, and increased pulmonary vascular and epithelial permeability, frequently resulting in acute respiratory failure culminating in often-fatal acute respiratory distress syndrome. Interleukin 8 (IL-8), a potent neutrophil attractant and activator, plays a significant role in acute lung injury via the formation of anti-IL-8 autoantibody:IL-8 complexes and those complexes interaction with FcγRIIa receptors, leading to the development of acute lung injury by, among other possible mechanisms, effecting neutrophil apoptosis. These complexes may also interact with lung endothelial cells in patients with acute respiratory distress syndrome. Continuing research of the role of neutrophils, IL-8, anti-IL-8 autoantibody:IL-8 complexes, and FcγRIIa receptors may ultimately provide molecular therapies that could lower acute respiratory distress syndrome mortality, as well as reduce or even prevent the development of acute lung injury altogether.

Well-differentiated papillary mesothelioma with invasive foci

Well-differentiated papillary mesotheliomas (WDPMs) are usually encountered as incidental findings in the peritoneal cavity in women. Most WDPMs are benign, and the histologic features that indicate a more aggressive course are controversial. We report 20 cases of WDPM, which contained invasive foci. Thirteen cases arose in the peritoneal cavity, 1 in a hernia sac, 3 in the pleural cavity, and 3 in hydroceles. The female:male ratio was 16:4, and age range was 7 to 74 years. Tumor was multifocal in 15 cases. Some tumors showed back-to-back papillae, a pattern mimicking invasion but discernible on pan-keratin stain as compressive crowding. True invasive patterns ranged from simple bland-appearing glands invading the stalks of the papillae to solid foci of invasive tumor of higher cytologic grade than the original WDPM. All 5 tested cases were negative for p16 deletion by fluorescence in situ hybridization, but 2/3 had abnormal karyotypes. Recurrences were seen in 8 patients, and in 4 multiple recurrences were documented. Of 16 patients with follow-up, 14 are alive from periods of 6 months to 6 years (average 3.5 y), and 2 have known recurrent disease. One patient died of disseminated tumor at 8 years but without histologic confirmation of the nature of the tumor. We conclude that WDPM with invasive foci in the papillae appear to be prone to multifocality and recurrence, but that they rarely give rise to life-threatening disease. We suggest that these lesions be called WDPM with invasive foci to alert clinicians to the possibility of recurrence.

Liquid biopsy in lung cancer: A perspective from members of the pulmonary pathology society

Liquid biopsy has received extensive media coverage and has been called the holy grail of cancer detection. Attempts at circulating tumor cell and genetic material capture have been progressing for several years, and recent financially and technically feasible improvements of cell capture devices, plasma isolation techniques, and highly sensitive polymerase chain reaction- and sequencing-based methods have advanced the possibility of liquid biopsy of solid tumors. Although practical use of circulating RNA-based testing has been hindered by the need to fractionate blood to enrich for RNAs, the detection of circulating tumor cells has profited from advances in cell capture technology. In fact, the US Food and Drug Administration has approved one circulating tumor cell selection platform, the CellSearch System. Although the use of liquid biopsy in a patient population with a genomically defined solid tumor may potentially be clinically useful, it currently does not supersede conventional pretreatment tissue diagnosis of lung cancer. Liquid biopsy has not been validated for lung cancer diagnosis, and its lower sensitivity could lead to significant diagnostic delay if liquid biopsy were to be used in lieu of tissue biopsy. Ultimately, notwithstanding the enthusiasm encompassing liquid biopsy, its clinical utility remains unproven.

#InSituPathologists: how the #USCAP2015 meeting went viral on Twitter and founded the social media movement for the United States and Canadian Academy of Pathology

Professional medical conferences over the past five years have seen an enormous increase in the use of Twitter in real-time, also known as “live-tweeting”. At the United States and Canadian Academy of Pathology (USCAP) 2015 annual meeting, 24 attendees (the authors) volunteered to participate in a live-tweet group, the #InSituPathologists. This group, along with other attendees, kept the world updated via Twitter about the happenings at the annual meeting. There were 6,524 #USCAP2015 tweets made by 662 individual Twitter users; these generated 5,869,323 unique impressions (potential tweet-views) over a 13-day time span encompassing the dates of the annual meeting. Herein we document the successful implementation of the first official USCAP annual meeting live-tweet group, including the pros/cons of live-tweeting and other experiences of the original #InSituPathologists group members. No prior peer-reviewed publications to our knowledge have described in depth the use of an organized group to “live-tweet” a pathology meeting. We believe our group to be the first of its kind in the field of pathology.

Immunohistochemistry of Pulmonary Biomarkers: A Perspective From Members of the Pulmonary Pathology Society

The use of immunohistochemistry for the determination of pulmonary carcinoma biomarkers is a well-established and powerful technique. Immunohistochemisty is readily available in pathology laboratories, is relatively easy to perform and assess, can provide clinically meaningful results very quickly, and is relatively inexpensive. Pulmonary predictive biomarkers provide results essential for timely and accurate therapeutic decision making; for patients with metastatic non-small cell lung cancer, predictive immunohistochemistry includes ALK and programmed death ligand-1 (PD-L1) (ROS1, EGFR in Europe) testing. Handling along proper methodologic lines is needed to ensure patients receive the most accurate and representative test outcomes.

Rapid On-Site Evaluation of Endobronchial Ultrasound–Guided Transbronchial Needle Aspirations for the Diagnosis of Lung Cancer: A Perspective From Members of the Pulmonary Pathology Society

CONTEXTn- Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) has emerged as a very useful tool in the field of diagnostic respiratory cytology. Rapid on-site evaluation (ROSE) of EBUS-TBNA not only has the potential to improve diagnostic yield of the procedure but also to triage samples for predictive molecular testing to guide personalized treatments for lung cancer.nnnOBJECTIVEn- To provide an overview of the current status of the literature regarding ROSE of EBUS-TBNA in the diagnosis of lung cancer.nnnDATA SOURCESn- An electronic literature search in PubMed and Google databases was performed using the following key words: cytology, lung cancer, on-site evaluation, rapid on-site evaluation, and ROSE EBUS-TBNA. Only articles published in English were included in this review.nnnCONCLUSIONSn- Rapid on-site evaluation can ensure that the targeted lesion is being sampled and can enable appropriate specimen triage. If available, it should be used with EBUS-TBNA in the diagnosis of lung cancer because it can minimize repeat procedures for additional desired testing (ie, molecular studies). Some studies have shown that ROSE does not adversely affect the number of aspirations, total procedure time of EBUS-TBNA, or the rate of postprocedure complications; it is also helpful in providing a preliminary diagnosis that can reduce the number of additional invasive procedures, such as mediastinoscopy. As EBUS technology continues to evolve, our knowledge of the role of ROSE in EBUS-TBNA for the diagnosis of lung cancer will also continue to grow and evolve.

Metalloproteinase-9 contributes to endothelial dysfunction in atherosclerosis via protease activated receptor-1

The atherosclerotic process begins when vascular endothelial cells undergo pro-inflammatory changes such as aberrant activation to dysfunctional phenotypes and apoptosis, leading to loss of vascular integrity. Our laboratory has demonstrated that exposure of mice to second hand smoke triggers an increase in expression of metalloproteinase-9. Further, metalloproteinase-9 released by second hand smoke—activated leukocytes may propagate pro-atherogenic alterations in endothelial cells. We have shown that levels of metalloproteinase-9 were increased in the plasma from apolipoprotein E deficient (ApoE-/-) mice exposed to second hand smoke relative to non-exposed controls. Moreover, we have collected data from two different, but complementary, treatments of second hand smoke exposed atherosclerotic mice. Animals received either cell specific metalloproteinase-9 directed siRNA to minimize metalloproteinase-9 expression in neutrophils and endothelial cells, or a pharmacological inhibitor of Bruton’s tyrosine kinase which indirectly limits metalloproteinase-9 production in neutrophils. These treatments reduced atherosclerotic changes in mice and improved overall vascular health. We also demonstrated that metalloproteinase-9 could activate endothelial cells and induce their apoptosis via cleavage of protease activated receptor-1. In summary, better understanding of metalloproteinase-9’s pathogenic capabilities as well as novel signaling pathways involved may lead to development of treatments which may provide additional benefits to atherosclerosis patients with a history of second hand smoke exposure.