The Daily Sign-Out

RBC Transfusion Associated with Increased Susceptibility to Lung Inflammation

Another recent article that I finally had a chance to read and ruminate on: Danielle Qing and colleagues from have published an intriguing article in the December 1, 2014 issue of the American Journal of Critical Care and Respiratory Medicine, "Red Blood Cells Induce Necroptosis of Lung Endothelial Cells and Increase Susceptibility to Lung Inflammation."  The article merits a read if you're interested in either transfusion medicine or lung pathology.

In both in vitro and murine models, RBC transfusion seems to prime lung inflammation through necroptosis (link to recent review article) of lung endothelial cells, followed by danger signal release of disease-associated molecular patterns, or DAMPs.  A novel finding in this study is that necroptosis may be an important mechanism that for cellular damage and organ dysfunction that is clinically observed associated with RBC transfusion. The methodology of using human lung microvascular endothelial cells and human RBCs stored under clinical conditions makes this model of injury more potentially relevant at the clinical level since it likely is a better approximation of what is occurring in vivo.

However, these findings quite jibe with the results of the TRISS trial published in NEJM last October.  One might expect that patients with sepsis who receive more RBC transfusions would have worse clinical outcomes than those who receive none or fewer transfusions.  But in this study similar clinical outcomes (mortality at 90 days and rates of ischemic events and use of life support) were observed in ICU patients with severe sepsis between those who received RBC transfusion at liberal transfusion threshold versus a restrictive threshold, even though the latter group received more transfusions.  It would be great to have a RCT that compared no to any RBC transfusions in this study population, measure necroptosis and DAMPs, and observe clinical outcomes.

Multifocal Micronodular Pneumocyte Hyperplasia Mimicking Miliary TB

Saturday morning interesting case report!

Download Multifocal pneumocyte hyperplasia mimicking miliary TB case report Lee 2014

 

NHLBI Workshop Report: Matrix Biology in Idiopathic Pulmonary Fibrosis

The June 2014 issue of American Journal of Pathology has this state-of-the-art review, based on a recent NHBLI workshop, of the various attributes of the lung extracellular matrix and its role in normal lung and in the development of IPF.

This is an "open access' (FREE) article and you can get CME for it too!

Here's a choice figure that nicely summarizes the biochemical and mechanical interactions between the fibroblast and the ECM:

Chronic Bronchitis and Chronic Obstructive Lung Disease Review

Although commonly thought of synonymous, or, at least, forming a spectrum, chronic bronchitis is distinct from COPD.  This review focuses on the pathophysiology of chronic bronchitis and goblet cell hyperplasia and the association between small airways disease and worse outcomes in patients with COPD.  A state-of-the-art review.

Victor Kim and Gerard J. Criner "Chronic Bronchitis and Chronic Obstructive Pulmonary Disease", American Journal of Respiratory and Critical Care Medicine, Vol. 187, No. 3 (2013), pp. 228-237.

doi: 10.1164/rccm.201210-1843CI

 

Abstract

Chronic bronchitis (CB) is a common but variable phenomenon in chronic obstructive pulmonary disease (COPD). It has numerous clinical consequences, including an accelerated decline in lung function, greater risk of the development of airflow obstruction in smokers, a predisposition to lower respiratory tract infection, higher exacerbation frequency, and worse overall mortality. CB is caused by overproduction and hypersecretion of mucus by goblet cells, which leads to worsening airflow obstruction by luminal obstruction of small airways, epithelial remodeling, and alteration of airway surface tension predisposing to collapse. Despite its clinical sequelae, little is known about the pathophysiology of CB and goblet cell hyperplasia in COPD, and treatment options are limited. In addition, it is becoming increasingly apparent that in the classic COPD spectrum, with emphysema on one end and CB on the other, most patients lie somewhere in the middle. It is known now that many patients with severe emphysema can develop CB, and small airway pathology has been linked to worse clinical outcomes, such as increased mortality and lesser improvement in lung function after lung volume reduction surgery. However, in recent years, a greater understanding of the importance of CB as a phenotype to identify patients with a beneficial response to therapy has been described. Herein we review the epidemiology of CB, the evidence behind its clinical consequences, the current understanding of the pathophysiology of goblet cell hyperplasia in COPD, and current therapies for CB.

 

Hypersensitivity Pneumonitis: recent updates

There have been two recent papers reviewing hypersensitivity pneumonitis (HP) that I had to summarize for myself and am sharing with you. While idiopathic pulmonary fibrosis/usual interstitial pneumonitis (IPF/UIP) may be the prototype for interstitial lung disease, I think that hypersensitivity pneumonitis is more frequently encountered or strongly considered in the differential diagnosis as a non-neoplastic lung biopsy specimen in “the daily sign-out,” at least in community-based general surgical pathology practice, and especially since the majority of IPF cases are now diagnosed by high-resolution CT scans without biopsy. Thus, being a practical sort, I suggest that a solid appreciation for the clinical, radiographic and pathological features of HP would help resolve many cases you might encounter in practice.

The paper by Selman, Pardo and King in the August 15, 2012 Am J Respir Crit Care Med (abstract) is more clinically oriented, while the paper by Herbst and Myers in the August 2012 Arch Pathol Lab Med (abstract) focuses on the role of surgical biopsy in the diagnosis of HP. I refer (defer?) to the Dail and Hammar Pulmonary Pathology textbook for the definitive description of the pathological findings in HP. (I also suggest that curling that textbook--volume 1--with 10 reps for each arm will give you beastly biceps in a few weeks’ time (hey--Kindle version anytime soon?).

One of the interesting aspects of the AJRCCM paper is the discussion on pathogenesis. The authors review the “2-hit” hypothesis: that there is a pre-existing genetic susceptibility and/or environmental factors, followed by exposure to one of the many antigens associated with HP. The antigens can be roughly divided into 3 groups: 1) thermophilic actinomycetes (Saccharopolyspora rectivirgula) as well as a variety of other fungi (Aspergillus, Penicillium spp); 2) a complex mixture of high- and low-molecular weight proteins from avian serum, feces, and feathers; 3) water-borne non-tuberculous mycobacteria. Importantly, no genetic factors have been consistently associated with HP. But certain polymorphisms have been identified that are associated with increased risk, including HLA-DR and -DQ polymorphisms, polymorphisms in the genes coding for TAP transport peptides MHC molecules for presentation to cytotoxic T cells, and polymorphisms in β type 8 (PSMB8)--an immunoproteasome catalytic subunit that participates in degradation of ubiquinated proteins to generate peptides for antigen presentation by class I MHC molecules. Finally, the authors discuss the role of cigarette smoking in HP. It is somewhat curious but known clinically that HP is less frequent in smokers compared to non-smokers. It is hypothesized that nicotine blunts the response to antigen exposure by its effects on decreasing macrophage activation, decreasing lymphocyte proliferation, and impairing T-cell function. However, when HP does occur in smokers, they tend to develop a chronic clinical course characterized by more recurrent episodes of disease and have a poorer survival rate compared with HP in non-smokers.

Classically (“”), HP is divided into acute, subacute, and chronic forms. However, there are no accepted clinical criteria that distinguish the various forms. Moreover, there is little information regarding the latency period between antigen exposure and disease onset. Indeed, it is uncertain that these divisions truly represent different stages of the disease.

Recently, cluster analysis studies suggest a two-cluster model for HP that correlates with observed clinical profile and the type of antigen exposure. Cluster 1 corresponds to the clinically “acute” form of HP. It is associated with an influenza-like syndrome occurring a few hours after a substantial exposure, more recurrent systemic symptoms, and a normal chest xray. Cluster 1 tends to occurs in individuals exposed to thermophilic actinomyces or fungi (≈”farmer’s lung”). Cluster 2 corresponds to the clinically “chronic” form of HP. It is associated with more features of severe, chronic disease (e.g. digital clubbing, hypoxemia, restrictive pattern by PFTs, fibrosis on HRCT scans) as well as slowly progressive chronic respiratory disease. This cluster tends to occur in individuals with bird antigen exposure. As pointed out by Herbst and Myers, this is the form one would be more likely to encounter in a biopsy situation as it mimics IPF/UIP or fibrotic NSIP. Of note, HRCT features that would favor HP over UIP/NSIP include lobular areas with decreased attenuation and air trapping, centrilobular nodules, and lack of lower zone predominance. The cluster analysis by 

Pathology of HP

As one may have surmised already, “acute” HP is just not biopsied very often so it is not very well-characterized. When specimens have been examined in which patients were diagnosed clinically with acute HP, the histologic findings resemble acute fibrinous organizing pneumonia. The “chronic” form of HP is much better studied and characterized as consists of a histologic triad of chronic interstitial inflammation, nonnecrotizing granulomas, and cellular bronchiolitis.  While this triad is seen in around 80% of patients with the clinical diagnosis of HP, it is not specific for HP.

The chronic interstitial infiltrate consists of a patchy and variably intense lymphoplasmacytic interstitial infiltrate that is frequently most intense around small bronchi and bronchioles. A salient point by Herbst and Myers (that I have noticed myself as well) is that this infiltrate may be accompanied by alveolar macrophages in adjacent alveoli with occasional aggregates of foamy macrophages suggesting lipid pneumonia. They also note that large numbers of foamy macrophages are frequently seen in pigeon-breeder’s disease. Importantly, necrosis and vasculitis are not seen. Nonnecrotizing granulomas may be found around respiratory bronchi or bronchioles as well as in the interstitium or in alveoli (so basically anywhere). These are “poorly-formed” (cf. sarcoidal granulomas) and composed of epithelioid histiocytes and Langhans’ giant cells. One helpful tip is the use of cathepsin K by IHC to help identify microgranulomas, particularly in “subacute” cases, but I think it would probably be helpful when granulomas don’t pop out at you. Another notable point is that the giant cells frequently contain cholesterol clefts, Schaumann bodies, and/or birefringent oxalate crystals. The cellular bronchiolitis is somewhat self-explanatory btu is primarily lymphocytic and extends into adjacent alveolar interstitium.

Herbst and Myers also point out some other significant “soft” findings that can be valuable in the diagnosis of HP. Small foci of organizing pneumonia pattern are found in up to 60% of patients diagnosed with HP. Small airways involvement may be found (more frequently in farmer’s lung than pigeon breeder’s disease) and adds an obstructive component. Mast cells are a constant finding and are frequently found in areas of interstitial fibrosis. And last but not least--interstitial fibrosis. Significant intersitial fibrosis is frequently found in patients who are biopsied months to years after the onset of symptoms as well as in those who have repetitive or persistent exposure to the putative antigen. Histologically, the fibrosis may have a UIP-like pattern identical to IPF.

As a personal note, I have found that the diagnosis of HP is typically made by carefully correlating the biopsy findings with the patient’s clinical history and radiographic findings in collaboration with the pulmonologist and radiologist. The paper by Selman, Pardo and King highlights important clinical findings of which we should be aware in consideration of the histological findings and the paper by Herbst and Myers emphasizes those histological features that might lead one to consider HP perhaps with less than adequate or preliminary clinical information. Both papers are timely and highly recommended but I hope I’ve been able to summarize them adequately for you.

Evidence for lung regeneration in an adult: case report

The conventional view is that lung growth and development ends around age 7 but a fascinating article in last week's NEJM (N Engl J Med 2012; 367:244-247July 19, 2012) suggests that lung growth can occur in adults.

Abstract

 A 33-year-old woman underwent a right-sided pneumonectomy in 1995 for treatment of a lung adenocarcinoma. As expected, there was an abrupt decrease in her vital capacity, but unexpectedly, it increased during the subsequent 15 years. Serial computed tomographic (CT) scans showed progressive enlargement of the remaining left lung and an increase in tissue density. Magnetic resonance imaging (MRI) with the use of hyperpolarized helium-3 gas showed overall acinar-airway dimensions that were consistent with an increase in the alveolar number rather than the enlargement of existing alveoli, but the alveoli in the growing lung were shallower than in normal lungs. This study provides evidence that new lung growth can occur in an adult human. 

Over the 15 year follow-up following right pneumonectomy, spirometry showed a 50% increase in FEV₁ and 35% increase in FVC (versus a predicted age-related decrease in both parameters). In addition, serial surveillance CT scans over the same period showed a gradual increase in tissue volume in the left lung, nearly doubling after surgery. I know it sounds like I'm gushing but the 3-dimensional CT reconstructions of the remaining left lung are just COOL!

But what is really orbital about this brief report is the use of a diffusion MRI study with "hyperpolarized helium-3 gas" to derive a quantitative estimate of acinar microstructure--and thus the development of new septae and evidence for lung regeneration. It took when a couple passes through this section to unwrap the radiology technique and how it relates to a microanatomical dimension (I'm somewhat embarassed to admit)--but check this out. The references on this technique are only a couple of years old, so this is some really cutting edge stuff.

Whether this unique case can be generalized would be an interesting study. The patient was very young when she was diagnosed with lung cancer and apparently had a robust daily exercise regimen--certainly not the typical lung cancer patient. But the evidence presented here is a credible challenge to a long-held assumption that adult lungs do not grow.

The new IASLC/ATS/ERS Lung Adencarcinoma Classification is a Stage-Independent Predictor of Survival

 I blogged on this new classification over a year ago when it was first published, but now papers are rolling out showing its utility.  My take on this recent paper below is that it confirms the idea of histologically grading lung ADC according to the predominant different subtypes (lepidic predominant grade 1 "well-differentiated" versus solid predominant being grade 3 "poorly-differentiated".  Moreover, it asserts that it is sufficient to regard only the predominant histologic type with regard to survival--which is a relief from going through the tedious task of estimating percentages of different minor subtypes after complete histologic examination.  Get this article--good for discussion with surgeons, oncologists, tumor conference, etc. 

The Novel Histologic International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society Classification System of Lung Adenocarcinoma Is a Stage-Independent Predictor of Survival.

Possible false positive interpretation of Napsin A staining in evaluating lung non-small cell carcinomas

Dr. Nelson Ordonez (MD Anderson Cancer Center, Houston) published a brief and very helpful article in the March 2012 American Journal of Surgical Pathology (abstract) that addresses a very practical issue of using IHC staining for Napsin A in evaluating primary lung NSCLC for confirmation of adenocarcinoma type.

Napsin A is normally expressed in type II alveolar pneumocytes but may also be localized immunohistochemically in intraalveolar macrophages presumably from phagocytosis.  The expression of both Napsin A and pro-surfactant protein B (ProSP-B) are regulated by thyroid transcription factor-1 (TTF-1), which is one of the common IHC stains initially performed on NSCLC not diagnostic for adenocarcinoma on routine H&E.  Napsin A is localized to lamellar bodies with ProSP-B and is thought to be involved in post-translational processing of ProSP-B.

This paper must be understood in the context of new IASLC lung adenocarcinoma classification and the algorithm recommended to histological type NSCLC.  Napsin A has emerged as a useful adjunct IHC stain, such as, in those cases in which a tumor is negative or equivocal for initial screening markers for both adenocarcinoma (ADC) and squamous cell carcinoma (SQC).  Until recently, Napsin A was found to be highly specific for lung ADC.  But, as Dr. Ordonez points out, several recent publications have found Napsin A positivity in lung squamous cell carcinomas and, thus, cast doubt over the high degree of specificity of Napsin A for lung adenocarcinoma and utility of this marker in this context.

Dr. Ordonez studied Napsin A expression by IHC in 90 primary lung SQC, including whole section and biopsy specimens, and 64 non-pulmonary SQC.  None of the primary lung SQC or the non-pulmonary SQC showed Napsin A positive staining in the malignant cells.

The key observation is the identification of entrapped type 2 pneumocytes and/or intraalveolar macrophages in desmoplastic areas adjacent to the tumor and in small clusters within the tumor--which could be a source of false-positive interpretation in SQC.  Dr. Ordonez found 5 biopsies in which these entrapped cells were difficult to distinguish from malignant cells and CK 5/6 was used in 2 of these cases to rule out the possibility that these were Napsin A-positive malignant squamous cells.

This is a critical distinction and very welcome contribution to the lung cancer pathology literature.  The reader should keep point this in mind, especially when evaluating biopsy material.  The illustrations are excellent in demonstrating these points and should also be kept close at hand.  Congratulations to Dr. Nelson Ordonez for an excellent paper.

Biomarkers in COPD

Chronic obstructive lung disease (COPD) is defined functionally as airflow limitation that is not fully reversible.  It is a MAJOR cause of morbidity and mortality in the U.S. and worldwide.  COPD has two distinct major, but often coexisting, forms that represent different manifestations of COPD: emphysema and chronic bronchitis.  Emphysema can be defined morphologically, either by radiography or pathology, while chronic bronchitis is defined clinically based upon the duration of productive cough and exclusion of other causes.  Treatment is focused on preventing progression of disease and the development of acute exacerbations, which are a major cause of hospitalizations, morbidity and mortality.  Common to both major forms is small airways inflammation and an abnormal inflammatory response either in large airways (chronic bronchitis) or in alveoli (emphysema).

COPD is also associated with low-grade systemic inflammation and biomarkers that could predict increased risk for mortality from progressive disease or acute exacerbations might be greatly beneficial in providing more intesive surveillance and treatment of this group.  A team of researchers led by Tufts University School of Medicine screened blood samples from people in the ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints) to see if inflammatory biomarkers could predict disease outcome (abstract).  The study included 1843 patients who were followed for 3 years.  168 of the 1843 patients (9.1%) died.  Serum or plasma levels of fibrinogen, chemokine ligand 18, surfactant protein D, C-reative protein, Clara cell secretory protein-16, interleukin-6, IL-8, and tumor necrosis factor-alpha were measured at recruitment and at subsequent visits.

The addtion of a panel of biomarkers significantly improved predictive power and was able to better predict outcomes compared with current clinical variables, including age, BODE index, and hospitalization history. The addition of IL-6 provided the most improvement of discriminatory power, but this was improved further with the addition of all biomarkers measured.

Aberrant Wnt1 and beta-catenin expression in NSCLC

This month's April 2011 Journal of Thoracic Oncology has an interesting paper by Xu and colleagues (abstract) that examines Wnt1 expression in non-small cell lung cancer (NSCLC) in relation to downstream Wnt signaling molecules, including beta-catenin, and correlates different marker expression with traditional clinicopathological parameters.

This is an immunohistochemical study of a tissue microarray composed of 262 NSCLC resected specimens.    The authors define aberrant beta-catenin expression as: 1) decreased membranous pattern in less than 70% of tumor cells, 2) cytoplasmic pattern of expression, or 3) nuclear pattern of expression.  As expected, the majority of patients are stage 1 or 2 but nearly 36% of the study population are never-smokers--over 50% in the adenocarcinoma histology group (!).  The authors found that Wnt1 overexpression was significantly associated with never-smoker status and ADC histology; aberrant beta-catenin expression was associated with SQC histology.  While each Wnt1 overexpression and aberrant beta-catenin expression were independently associated with decreased OS regardless of TNM stage, patients that demonstrated both had worse OS than other combinations of Wnt1/beta-catenin expression.  Further, Wnt1/beta-catenin expression was also an independent factor adjusted by stage, pleural invasion, lymphatic invasion, ECOG PS or stage, age, gender, histology, and p53 expression.

A few comments about this paper.  One significant caveat to the findings is the over-representation of never smokers (35%) in this Asian study population, especially nearly 54% of never smokers in the ADC group, compared to a more typical American population in a community hospital setting (about 10%).  Overexpression of Wnt1 was significantly associated with never-smoking and as well as ADC histology, but, somewhat paradoxically, Wnt1 overexpression was associated with significantly shorter overall survival.  Unfortunately, the authors do not break this further down into Wnt1 overexpression and OS with respect to histological type--perhaps some SQCs showing Wnt1 overexpression and dismal OS are skewing the data here since one would expect never-smokers with ADC to have a better prognosis in general.  Another is the usual issues with using TMAs to represent complex heterogenous tumors.  The authors do not sufficiently describe from where they target obtaining cores for constructing the TMA--are they targeting the invasive margin, the central tumor, wherever?  what about mixed histology tumors?  These are critical methodological issues--especially when extrapolating the data concerning marker expression.  One admirable feature of this paper is the clear definition, supported by appropriate photomicrographs, of "aberrant" beta-catenin expression.  As I am currently working on projects that are similarly assessing beta-catenin expression in NSCLC, I found this very helpful in assessing this paper's findings.