Invasion of the inner and outer layers of the visceral pleura in pT1 size lung adenocarcinoma measuring ≤3?cm: correlation with malignant aggressiveness and prognosis

Visceral pleural invasion (VPI) is defined as penetration by cancer cells of the elastic layer of the pleura. The purpose of this retrospective study was to compare the effect of invasion of the inner elastic layer of the pleura on survival to that of invasion of the outer elastic layer. One hundred twenty-four pT1 size lung adenocarcinomas were examined for visceral pleural invasion, which was classified into three types: no pleural invasion (NPI), invasion of the inner elastic layer only (IEL), and invasion of both inner and outer elastic layers (OEL). The relationship between the types of VPI and the prognosis was analyzed by univariate and multivariate analyses. Seventy-three (59?%) cancers showed NPI, while 51 cancers showed invasion of the pleura [(IEL) in 26 (21?%), OEL in 25 (20?%)]. The 5-year survival was 81, 60, and 37?% for patients with NPI, IEL, and OEL, respectively. Survival was poorest in patients with OEL (P?<?0.01). Invasion of the outer elastic layer was also significantly associated with lymph node metastasis and frequent lymphatic involvement, micropapillary pattern, higher stromal invasion grade, and presence of small cluster invasion within tumors. Univariate analysis showed a significant relationship between invasion of the outer elastic layer and poor prognosis. However, multivariate analysis identified lymph node metastasis as the most significant predictor of poor prognosis. Analysis of invasion of the inner and outer visceral pleura is important; invasion of the outer elastic layer correlates with poor prognosis in pT1 size lung adenocarcinomas.     

Visceral pleural invasion in lung cancer: recognizing histologic parameters that impact staging and prognosis

Visceral pleural involvement (VPI) is a critical component in the staging of non-small cell lung carcinoma (NSCLC). Tumors < or =3 cm that involve the visceral pleura are classified as T2 lesions, underscoring the prognostic significance of this histologic parameter. Accurate staging of small NSCLCs depends on appropriately assessing the presence or absence of VPI. Elastic stains can be instrumental in detecting disruptions of the visceral pleural elastic layer by tumor, a finding that has prognostic and staging implications similar to tumor that is present on the visceral pleural surface.     

The diagnosis and significance of visceral pleural invasion in lung carcinoma. Histologic predictors and the role of elastic stains

Invasion of the visceral pleura is an important component of lung carcinoma staging, and in some studies is an independent prognostic indicator. Evaluation of invasion by H&E may be indeterminate. Elastic stains can be helpful but are performed rarely. We reviewed all lung carcinoma resections from 1993 for 13 histologic features potentially predictive of pleural invasion. Of 57 resections, 20 were indeterminate by H&E. Verhoeff-Van Gieson (VVG) stain revealed invasion in 8 cases, increasing the pathologic stage in 1. VVG stain was negative in 12 cases, 2 of which had been falsely reported as positive, decreasing the stage in 1. Angiolymphatic invasion and single-cell spread were significant predictors of invasion. Absence of both or the presence of intervening aerated parenchyma predicted lack of involvement in all cases. Elastic stains can provide prognostically important information, changing the pathologic stage in 4% of lung carcinoma resections overall and in 10% of cases indeterminate by H&E for pleural invasion.     

Interobserver agreement on what constitutes visceral pleural invasion by non-small cell lung carcinoma: an internet-based assessment of international current practices

Visceral pleural invasion (VPI) increases the T category of non-small cell lung carcinomas (NSCLCs) that otherwise only meet T1 criteria to T2. The American Joint Committee on Cancer provides no guidelines on what constitutes VPI. Penetration beyond the visceral pleural elastic layer (VPEL) has been proposed as the minimum criterion but is not internationally accepted. The purposes of this study were to elucidate current international practices regarding assessment of VPI and identify histologic features pathologists consider necessary for VPI. We examined responses to an online quiz consisting of 15 NSCLCs adjacent to or involving the visceral pleura. Of 103 participants from 22 countries, 84.5% were in academic practice; 42.7% had a subspecialty interest in pulmonary pathology. Interobserver percentage agreement about whether VPI was present, absent, or indeterminate ranged from 36.9% to 93.2% (mean, 73.0%). The K for participants for all quiz cases was 0.35. There was considerable diagnostic variability in cases with extensive pleural elastosis and when tumor cells were intermingled with the VPEL. It seems that the majority of participants consider penetration of the VPEL necessary and also sufficient to categorize VPI as present. However, the formation of internationally recognized guidelines for assessing VPI by NSCLC is likely to improve diagnostic consensus.     

Classification of parietal pleural invasion at adhesion sites with surgical specimens of lung cancer and implications for prognosis

Parietal pleural invasion of non-small cell lung cancer (NSCLC) is a factor for poor prognosis, and a tumor of any size that invades the parietal pleura is classified as T3. However, with microscopic invasion beyond elastic fibers of the visceral pleura but no penetration to the parietal pleura at tight adhesion sites (we term this p1–3), classification as to the T factor is unclear. Among 1,179 consecutive patients with NSCLCs who underwent curative surgery between 1980 and 2002, 20 were in this category. Here, a comparison was made with subgroups of p stages IB, II, and IIIA with regard to histology, pleural invasion, and survival rates. To maximize the power of assessing prognostic potential, we set the significance level at 0.10, one-sided. The p1–3 condition sites of the 20 cases were the parietal pleura for 17 cases and the pericardium, diaphragm, and chest wall for one each of the remainder. The 5-year survival rate for these p1–3 patients was 71.6%. Significant differences were observed between p1–3 and IIIA groups. Although the 5-year survival rates did not significantly differ between p1–3 and T3N0 or unequivocal T3 subgroups, the prognosis of p1–3 patients was rather better than that of T3 and identical to T2. It was demonstrated that p1–3 status is not a factor warranting T3 classification for NSCLCs. Considering the prognosis, pathologic p1–3 tumors should be managed as a T2 disease for the present.     

Are elastic stain and specialty sign out necessary to evaluate pleural invasion in lung cancers?

The seventh edition of American Joint Committee on Cancer (AJCC) staging system assigns lung cancers with visceral pleural invasion in the tumor size of 3 cm or less than 3 cm as T2 and without pleural invasion as T1. However, it may be difficult to distinguish with certainty between PL0 (no pleural invasion) and PL1 (extends through the elastic layer) on routine hematoxylin and eosin (H&E) stain. In this study, 25 cases of peripherally located lung adenocarcinoma were retrieved from the surgical pathology archives at the Asan Medical Center from May through June 2009. One representative H&E-stained slide was selected from each case and circulated to 31 pathology trainees and board-certified pathologists at Asan Medical Center who evaluated presence or absence of pleural invasion on H&E-stained slides. Elastic stain was used to determine the final status of pleural invasion for each case. The concordance rate of all pathologists with elastic stain results was, overall, 60.5%. The concordance rate of 2 lung specialists was 64%, better than the remaining faculty (54.7%). Fellows' and residents' evaluations were slightly more concordant than those of faculty responses (faculty overall, 56.4%; fellows, 62%; residents, 63.6%), but this difference was not statistically significant (P = .228). Our results confirm that pleural invasion status is difficult to discern with certainty on H&E-stained sections alone. Therefore, we recommend the routine use of elastic stain in evaluation of pleural invasion in all peripherally located lung cancers. Furthermore, our study indicates that subspecialty sign out may be preferable in evaluation of pleural invasion status.     

Use of oolong tea extract (OTE) for elastin staining and enhancement in ultrathin sections

To assess the usefulness of oolong tea extract (OTE) staining for connective tissue observation, we examined the visceral pleural mesothelium of rat lung by transmission electron microscope. Four kinds of electron microscopic staining methods (routine, tannic acid, OTE in distilled water, and OTE in 0.1M phosphate buffer) were compared to determine the most suitable method for electron microscopic observation of ultrathin sections. Elastin (elastic laminae) was selectively stained by tannic acid and both water and buffered OTE. Except for elastin, connective tissue and cell ultrastructures were also electron enhanced by tannic acid and both water and buffered OTE staining. However, using water OTE, the electron-dense filaments (10–12nm in diameter) were obscured. In tannic acid staining, the unit membranes of the visceral pleural mesothelial cells were weaker as compared with routine and buffered OTE stains. Thus, the buffered OTE staining method is a highly useful technique for connective tissue observation and electron-enhanced staining in transmission electron microscopic preparations.     

The yellow nail syndrome. Light and electron microscopic aspects of the pleura

The yellow nail syndrome is a rare cause of recurrent pleural effusions. We studied a case of this entity, placing special emphasis on the microscopic and ultrastructural aspects of the pleural lymphatics. The patient had the classic symptoms of recurrent bilateral pleural effusions, yellow, dystrophic fingernails and toenails, and lower-limb edema. To control the pleural effusions, a left parietal pleurectomy was performed. Histologic study showed both pleura to be thickened with fibrosis and chronic inflammatory infiltration. The lymphatic capillaries in the visceral pleura were dilated. Electron microscopy confirmed the lymphatic nature of these capillaries. We believe that these ectatic lymphatic capillaries suggest a downstream obstruction to the lymph drainage.     

Microscopic anatomy of the visceral fasciae

The term ‘visceral fascia’ is a general term used to describe the fascia lying immediately beneath the mesothelium of the serosa, together with that immediately surrounding the viscera, but there are many types of visceral fasciae. The aim of this paper was to identify the features they have in common and their specialisations. The visceral fascia of the abdomen (corresponding to the connective tissue lying immediately beneath the mesothelium of the parietal peritoneum), thorax (corresponding to the connective tissue lying immediately beneath the mesothelium of the parietal pleura), lung (corresponding to the connective tissue under the mesothelium of the visceral pleura), liver (corresponding to the connective tissue under the mesothelium of the visceral peritoneum), kidney (corresponding to the Gerota fascia), the oesophagus (corresponding to its adventitia) and heart (corresponding to the fibrous layer of the pericardial sac) from eight fresh cadavers were sampled and analysed with histological and immunohistochemical stains to evaluate collagen and elastic components and innervation. Although the visceral fasciae make up a well‐defined layer of connective tissue, the thickness, percentage of elastic fibres and innervation vary among the different viscera. In particular, the fascia of the lung has a mean thickness of 134 μm (± 21), that of heart 792 μm (± 132), oesophagus 105 μm (± 10), liver 131 μm (± 18), Gerota fascia 1009 μm (± 105) and the visceral fascia of the abdomen 987 μm (± 90). The greatest number of elastic fibres (9.79%) was found in the adventitia of the oesophagus. The connective layers lying immediately outside the mesothelium of the pleura and peritoneum also have many elastic fibres (4.98% and 4.52%, respectively), whereas the pericardium and Gerota fascia have few (0.27% and 1.38%). In the pleura, peritoneum and adventitia of the oesophagus, elastic fibres form a well‐defined layer, corresponding to the elastic lamina, while in the other cases they are thinner and scattered in the connective tissue. Collagen fibres also show precise spatial organisation, being arranged in several layers. In each layer, all the fibrous bundles are parallel with each other, but change direction among layers. Loose connective tissue rich in elastic fibres is found between contiguous fibrous layers. Unmyelinated nerve fibres were found in all samples, but myelinated fibres were only found in some fasciae, such as those of the liver and heart, and the visceral fascia of the abdomen. According to these findings, we propose distinguishing the visceral fasciae into two large groups. The first group includes all the fasciae closely related to the individual organ and giving shape to it, supporting the parenchyma; these are thin, elastic and very well innervated. The second group comprises all the fibrous sheets forming the compartments for the organs and also connecting the internal organs to the musculoskeletal system. These fasciae are thick, less elastic and less innervated, but they contain larger and myelinated nerves. We propose to call the first type of fasciae ‘investing fasciae’, and the second type ‘insertional fasciae’.     

Tight junction proteins contribute to barrier properties in human pleura

The permeability of pleural mesothelium helps to control the volume and composition of the liquid lubricating pleural surfaces. Information on pleural barrier function in health and disease, however, is scarce. Tissue specimens of human pleura were mounted in Ussing chambers for measurement of transmesothelial resistance. Expression of tight junction (TJ) proteins was studied by Western blots and immune fluorescence confocal microscopy. Both visceral and parietal pleura showed barrier properties represented by transmesothelial resistance. Occludin, claudin-1, -3, -5, and -7, were detected in visceral pleura. In parietal pleura, the same TJ proteins were detected, except claudin-7. In tissues from patients with pleural inflammation these tightening claudins were decreased and in visceral pleura claudin-2, a paracellular channel former, became apparent. We report that barrier function in human pleura coincides with expression of claudins known to be key determinants of epithelial barrier properties. In inflamed tissue, claudin expression indicates a reduced barrier function.     

Clinicopathology of stromal invasion in lung adenocarcinoma

In the World Health Organization classification, lung adenocarcinoma with mixed subtypes is defined as invasive carcinoma with evidence of vascular, pleural, or stromal invasion. The histological criteria for stromal invasion, however, are not clearly established. A total of 157 peripheral pure bronchioloalveolar carcinoma (BAC) or lung adenocarcinoma with mixed BAC and others were reviewed. All cases had been resected between 1986 and 2000 and measured ≤30 mm in maximum dimension. Destruction of alveolar framework (DAF) was defined as distortion or discontinuity of the alveolar framework by tumor growth. The extra-alveolar area involvement (EAAI) was defined as tumor growth outside the alveolar framework, which includes the following areas: bronchial wall, perivascular connective tissue and/or the vascular wall, interlobular septum and the visceral pleura. Survival of patients with adenocarcinoma without DAF ( n  = 41) was 100%. Even when adenocarcinoma involved DAF and lacked EAAI ( n  = 21), survival was 100%. The 5 year survival rate of groups with two invasion signs ( n  = 34) was 90.1%, and that of groups with three to five invasion signs ( n  = 61) was 66.7%. Tumor growth outside the alveolar framework is the hallmark of stromal invasion.     

Sensory receptors in the visceral pleura: neurochemical coding and live staining in whole mounts

Today, diagnosis and treatment of chest pain related to pathologic changes in the visceral pleura are often difficult. Data in the literature on the sensory innervation of the visceral pleura are sparse. The present study aimed at identifying sensory end-organs in the visceral pleura, and at obtaining more information about neurochemical coding. The immunocytochemcial data are mainly based on whole mounts of the visceral pleura of control and vagally denervated rats. It was shown that innervation of the rat visceral pleura is characterized by nerve bundles that enter in the hilus region and gradually split into slender bundles with a few nerve fibers. Separate nerve fibers regularly give rise to characteristic laminar terminals. Because of their unique association with the elastic fibers of the visceral pleura, we decided to refer to them as "visceral pleura receptors" (VPRs). Cryostat sections of rat lungs confirmed a predominant location on mediastinal and interlobar lung surfaces. VPRs can specifically be visualized by protein gene product 9.5 immunostaining, and were shown to express vesicular glutamate transporters, calbindin D28K, Na+/K+-ATPase, and P2X3 ATP-receptors. The sensory nerve fibers giving rise to VPRs appeared to be myelinated and to have a spinal origin. Because several of the investigated proteins have been reported as markers for sensory terminals in other organs, the present study revealed that VPRs display the neurochemical characteristics of mechanosensory and/or nociceptive terminals. The development of a live staining method, using AM1-43, showed that VPRs can be visualized in living tissue, offering an interesting model for future physiologic studies.     

Na+-glucose cotransporter is also expressed in mesothelium of species with thick visceral pleura

Molecular evidence for Na+-glucose cotransporter (SGLT1) in rabbit pleural mesothelium has been recently provided, confirming earlier functional findings on solute-coupled liquid absorption from rabbit pleural space. In this research we checked whether SGLT1 is also expressed in pleural mesothelium of species with thick visceral pleura, which receives blood from systemic circulation, but drains it into pulmonary veins. To this end immunoblot assays were performed on total protein extract of scraped visceral and parietal mesothelium of lambs and adult sheep, and of a human mesothelial cell line. All of them showed SGLT1 specific bands. Moreover, confocal immunofluorescence images of lamb pleural mesothelium showed that SGLT1 is located in apical membrane. Therefore, a solute-coupled liquid absorption should also occur from pleural space of species with thick visceral pleura. Because of this protein-free liquid entering interstitium between visceral mesothelium and capillaries, inherent Starling forces should be different than hitherto considered, and visceral pleura capillaries could absorb liquid even in these species.     

Anisotropic Nature of Mouse Lung Parenchyma

Lung parenchyma is normally considered to be isotropic, that is, its properties do not depend upon specific preferential directions. The assumption of isotropy is important for both modeling of lung mechanical properties and quantitative histologic measurements. This assumption, however, has not been previously examined at the microscopic level, in part because of the difficulty in large lungs of obtaining sufficient numbers of small samples of tissue while maintaining the spatial orientation. In the mouse, however, this difficulty is minimized. We evaluated the parenchymal isotropy in mouse lungs by quantifying the mean airspace chord lengths (Lm) from high-resolution histology of complete sections surrounded by an intact continuous visceral pleural membrane. We partitioned this lung into 5 isolated regions, defined by the distance from the visceral pleura. To further evaluate the isotropy, we also measured Lm in two orthogonal spatial directions with respect to the section orientation, and varied the sample line spacing from 3 to 280 μm. Results show a striking degree of parenchymal anisotropy in normal mouse lungs. The Lm was significantly greater when grid lines were parallel to the ventral–dorsal axis of the tissue. In addition the Lm was significantly smaller within 300 μm of the visceral pleura. Whether this anisotropy results from intrinsic structural factors or from nonuniform shrinkage during conventional tissue processing is uncertain, but it should be considered when interpreting quantitative morphometric measurements made in the mouse lung.     

Pulmonary adenocarcinoma simulating malignant mesothelioma.

Adenocarcinoma of the lung with pleural involvement frequently resembles pleural epithelioid mesothelioma clinically as well as macro- and microscopically. Special stains, immunohistochemical studies, and electron microscopic studies are needed to differentiate these 2 tumors. We report a case of pleural involvement by adenocarcinoma, mimicking in the hematoxylin-eosin stain an epithelioid mesothelioma, correctly identified only after immunohistochemical and electron microscopic examinations.     

呼吸过程胸膜腔内压和肺泡壁压强的产生与变化规律

生理学教科书都论及胸膜腔压强、肺泡壁压强和肺内压,但都未阐明清楚。本研究揭示胸膜腔内压、肺泡壁压强和肺泡内压的产生及变化规律。结果表明,胸膜腔内压是肺胸膜所受扩张力或压缩力的压强产生。平静吸气时,胸廓扩张,胸膜腔负压增大。平静呼气时,胸廓缩小,但胸廓、肺仍处于扩张状态,胸膜腔内仍为负压。随着胸廓缩小,负压减小。在用力呼气时肺胸膜、壁胸膜挤压胸膜腔,其内才产生正压。肺泡壁压强是胸膜腔内压、肺组织内的压强与肺泡壁附加压强的代数和。肺泡壁附加压强用球形弹性膜拉普拉斯公式计算。肺泡内压取决于肺泡壁张缩运动快慢和气道阻力大小。     

Prognostic significance of micropapillary pattern in lung adenocarcinoma and expression of apoptosis-related markers: caspase-3, bcl-2, and p53

We evaluated the clinicopathological characteristics and prognostic significance of lung adenocarcinoma with micropapillary pattern (MPP) and analyzed the expression of apoptosis-related markers: caspase-3, bcl-2, and p53. A series of 166 lung adenocarcinoma that had been surgically resected between 2004 and 2009 were reviewed. Histopathologic patterns, presence of tumor necrosis, mitosis, lymphovascular and perineural invasion, the status of pleura, and tumor differentiation were examined. Of the 166 patients; 71 were stage I, 35 stage II, 51 stage III, and nine stage IV. Histologically they were divided into two groups: MPP-positive (n = 55) and MPP-negative (n = 111). The following items were significantly more frequent in the MPP positive group: female gender (p = 0.03), lymph node metastasis (p = 0.031), and pleural invasion (p = 0.045). Age, smoking status, tumor stage, lymphatic invasion, perineural invasion, mitotic count, and survival rates had no statistically significant difference between groups (p > 0.05). In MPP positive tumors, visceral pleural invasion was identified significantly more frequent than in MPP negative tumors, at stage I. Tumors with MPP showed elevated expressions of caspase-3 (94.5%), p53 (60%), and bcl-2 (54.5%). In MPP positive group, the expression of these three markers had no statistically significant impact on survival. In whole population, bcl-2 expression was correlated with a better outcome. We conclude that MPP is associated with poor prognostic factors both in early and late stages in lung adenocarcinoma. Bcl-2 provides prognostic information independent from the MPP.     

Cytologic detection of malignancy in pleural effusion: a review of 5,255 samples from 3,811 patients

A retrospective analysis of 5,255 pleural effusion specimens from 3,811 patients was undertaken to determine the accuracy of cytopathologic correlation with pleural biopsy, the detection rate of malignancy by cytology, and the frequency distribution of malignant effusions according to age group. The cytopathologic correlation was 96.5% accurate, with 0.1% false-positive results and 0.18% false-negative results by cytology. The sensitivity of cytologic detections was 6.7% higher than that of pleural biopsy. Frequency analysis showed that the incidence of carcinoma of the lung, the most common cause of malignant effusion, is not sex based. Adenocarcinoma of the lung was the most frequent type of malignancy found in pleural effusions. It represented 79% of lung carcinomas that metastasized to pleura, accounting for 40% of all malignant pleural effusions. In young adults, lymphoreticular malignancies were the most common cause of malignant effusions.