Assessment of in vitro particle dosimetry models at the single cell and particle level by scanning electron microscopy.

BACKGROUND: Particokinetic models are important to predict the effective cellular dose, which is key to understanding the interactions of particles with biological systems. For the reliable establishment of dose-response curves in, e.g., the field of pharmacology and toxicology, mostly the In vitro Sedimentation, Diffusion and Dosimetry (ISDD) and Distorted Grid (DG) models have been employed. Here, we used high resolution scanning electron microscopy to quantify deposited numbers of particles on cellular and intercellular surfaces and compare experimental findings with results predicted by the ISDD and DG models. RESULTS: Exposure of human lung epithelial A549 cells to various concentrations of differently sized silica particles (100, 200 and 500 nm) revealed a remarkably higher dose deposited on intercellular regions compared to cellular surfaces. The ISDD and DG models correctly predicted the areal densities of particles in the intercellular space when a high adsorption ("stickiness") to the surface was emulated. In contrast, the lower dose on cells was accurately inferred by the DG model in the case of "non-sticky" boundary conditions. Finally, the presence of cells seemed to enhance particle deposition, as aerial densities on cell-free substrates were clearly reduced. CONCLUSIONS: Our results further validate the use of particokinetic models but also demonstrate their limitations, specifically, with respect to the spatial distribution of particles on heterogeneous surfaces. Consideration of surface properties with respect to adhesion and desorption should advance modelling approaches to ultimately predict the cellular dose with higher precision.

Salt-wasting bronchorrhea and its mechanisms.

A 56-year old woman, with the diffuse form of bronchioloalveolar cell carcinoma, developed massive bronchorrhea, resulting in severe fluid and electrolyte depletion when her oral intake was compromised. Chemical analysis of the bronchial secretions and the ultrastructural features of the tumor cells support the concept of an active secretory process. The lactic dehydrogenase (LDH) isoenzyme pattern of the fluid is similar to that found in fetal cells. The neoplastic cells may acquire a more primitive LDH pattern.

Bronchiolo-alveolar carcinoma with nodal metastases. An ultrastructural study.

A case of bronchiolo-alveolar carcinoma of the lung was studied by light and electron microscopy. Type II granular pneumocytes were seen in the lymph node metastases of the tumor, a finding not reported previously. We feel that the presence of these cells in metastatic foci indicates their neoplastic nature, and provides evidence that bronchiolo-alveolar carcinoma arises from type II cells.

Pulmonary alveolar cell carcinoma. Fine structural and in vitro study of a case and critical review of this entity.

Alveolar cell carcinoma is an unusual pulmonary neoplasm composed of cells with the ultrastructural features of granular pneumocytes. In the past this lesion has been grouped with peripheral well-differentiated mucin-secreting adenocarcinomas under the heading of bronchiolo-alveolar cell carcinoma. Because the existence of alveolar cell carcinoma as a distinct entity has been disputed, we examined a case ultrastructurally and confirmed that the neoplastic cells exhibit granular pneumocyte differentiation (lamellar bodies and abundant surface microvilli). In addition, we have growth this tumor in organ culture for up to 5 months and have documented the persistence of granular pneumocyte differentiation during this period. The accumulated evidence from human and animal studies that the granular pneumocyte may undergo neoplastic transformation is briefly reviewed. We conclude that alveolar cell carcinoma is a distinct entity; however, the elucidation of its natural history must await series that separate this lesion from other pulmonary carcinomas.

Observations on bronchiolo-alveolar carcinomas with special emphasis on localized lesions. A clinicopathological, ultrastructural, and immunohistochemical study of 11 cases.

Pathological and clinical features in early localized mucinous and nonmucinous bronchiolo-alveolar carcinomas (BAC) have not been adequately compared. In an attempt to characterize such lesions, we studied the clinicopathological, ultrastructural, and immunohistochemical features of three mucinous and eight nonmucinous BAC (four Clara cell, four Type II pneumocyte) along with one sheep pulmonary carcinoma (SPC). Tumor border, associated fibroplasia, tumor cell incohesion, lymphocytic infiltrate, T-lymphocytes, Langerhans cells (LC), and Leu-M1 and OC 125 immunoreactivity were evaluated. Localized tumors of both types had a similarly favorable prognosis, even when the tumor size was greater than 3 cm or showed more complex histology. Type II pneumocyte carcinomas with tumor cell disassociation and desquamation or a pseudomesotheliomatous phenotype did poorly. Clara cell and type II carcinomas elicited an LC and T-lymphocyte immune response. LC and T-lymphocytes were absent in mucinous BAC and SPC. All of the three mucinous and three of the seven nonmucinous BAC were Leu-M1 negative, indicating that Leu-M1 may not distinguish between BAC and mesothelioma, especially in a small biopsy specimen. Tumors with absent or slight Leu-M1 immunoreactivity had a favorable outcome irrespective of cell type and presence or absence of LC. Inasmuch as OC 125 was negative in all cases of BAC, OC 125 may be a useful adjunct in the immunodiagnosis of mesothelioma. Our investigation supports the view that two different groups of tumors are assembled under the single nosologic entity of BAC: one, mucinous, which grows along an unaltered pulmonary alveolar framework and elicits a B-lymphocytic response, and the other, nonmucinous, which induces desmoplasia and elicits an LC and T-lymphocytic response. Only mucinous BAC represent a biologic entity distinct from conventional pulmonary adenocarcinomas.

A histochemical and ultrastructural study of adenocarcinoma of the lung.

Twenty-five cases of solitary nodular adenocarcinoma of the human lung were studied histochemically and ultrastructurally and their morphological characteristics were compared to the cells observed in the control lungs. Adenocarcinoma cells of the human lung may be classified into following four types: Type A--cells resembling the bronchial goblet cell; Type B--cells resembling the mucous cell of the bronchial gland; Type C--cells resembling the type II alveolar lining cell; and Type D--cells resembling the nonciliated bronchiolar cell. Twenty-one cases belonging to Type D (84%) and two cases to Type B (8%), and one case each to Types A (4%) and C (4%). For the histogenesis of adenocarcinoma of the human lung, nonciliated bronchiolar epithelium may be the most important. A comparison of 10 cases of bronchiolo-alveolar carcinoma with 15 cases of ordinary (acinar and papillary) adenocarcinoma revealed no clear differences either histochemically or ultrastructurally.

Intravascular bronchiolo-alveolar tumor (IVBAT): A low-grade sclerosing epithelioid angiosarcoma of lung.

Intravascular bronchiolo-alveolar tumor (IVBAT) is a rare and highly distinctive pulmonary tumor of disputed cellular nature. Both epithelial and endothelial differentiation of this neoplasm have been suggested. We have studied multiple nodules of IVBATs from three patients by light and electron microscopy and by immunohistochemical methods for Factor VIII-related antigen (FVIII RAG). Our light and ultrastructural studies are in essential agreement with the previous suggestion of the endothelial nature of the neoplasm and our demonstration of the presence of FVIII RAG in many of the tumor cells offers new evidence strongly supportive of their endothelial differentiation. We believe that IVBAT and a group of extrapulmonary tumors described as epithelioid hemangioendothelioma and endovascular papillary angioendothelioma are similar biologically indolent neoplasms of epithelioid and dendritic endothelial cells characterized by stromal sclerosis, intravascular spread, a low incidence of metastases and slow clinical evolution. Thus, we regard IVBAT as a low-grade sclerosing angiosarcoma of the lung.

Morphologic aspects of nuclear bodies in a case of bronchiolar-alveolar carcinoma of the lung.

The ultrastructural features of a bronchiolar-alveolar carcinoma of the lung are described wherein the presence of nuclear bodies in many of the tumor cells were noted. Although these bodies are not viral elements, it is surmised that they may be virus associated and consequently possibly related to the etiology of this tumor. A review of the ultrastructural findings in the pulmonary adenomatosis of sheep is presented, and these are compared with those in human disease. Experimental evidence of an infectious agent responsible for human lung carcinomas is discussed, and possible avenues for future investigation are delineated.

The role of electron microscopy in the diagnosis of unusual peripheral lung tumors.

The ultrastructure of the lung provides a cytomorphologic basis for the identification of unusual pulmonary neoplasms or unusual histologic variants of more common pulmonary lesions. Comparison of tumor cells with bronchioloalveolar lining cells and with pleural components has aided in the diagnosis of a spindle cell variant of a peripheral neuroendocrine cell tumor (carcinoid) and a tumor composed of cells resembling bronchioloalveolar epithelium (sclerosing hemangioma of lung).

Aerogenous spread of primary lung adenocarcinoma induces ultrastructural remodeling of the alveolar capillary endothelium.

To determine whether pulmonary alveolar capillaries manifest ultrastructural remodeling at areas of neoplastic invasion of primary lung adenocarcinomas, we examined 17 well-differentiated adenocarcinomas of lung (2 bronchioloalveolar and 15 papillary adenocarcinomas) by electron microscopy. The expression of vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA) was demonstrated by immunohistochemical stainings. VEGF messenger RNA (mRNA) isoforms were detected by reverse-transcription polymerase chain reaction (RT-PCR) in alveolar walls microdissected from normal and tumor-associated tissues. Cytoplasm of neoplastic cells expressed VEGF protein in all patients. Endothelial cell nuclei of alveolar capillaries showed positive reaction for PCNA. Alveolar capillary lumina were distended like venules, and some intercellular junctions remained open. The cytoplasm of the capillary endothelial cells was enlarged and developed numerous organelles such as Weibel-Palade bodies and vesiculovacuolar organelles, in contrast to marked attenuation in their normal counterpart. Capillary sprouting occurred from proper alveolar capillaries in 2 patients. Cytoplasmic segments became extremely attenuated and developed diaphragm-like fenestrae in 65% of the patients. A relatively higher expression of diffusable isoforms of VEGF mRNA was seen in the tumor-bearing alveolar walls than in normal walls. Expression of KDR (one of the VEGF receptors) mRNA in tumor exceeded that in normal tissues. These results suggest that diffusable isoforms of VEGF mRNA released from the neoplastic cells are deeply involved in the induction of growth activity of alveolar capillary endothelial cells as much as in the characterization of tumor-associated microvessels in primary lung adenocarcinomas.

Analysis of cell type and radiographic presentation as predictors of the clinical course of patients with bronchioalveolar cell carcinoma.

STUDY OBJECTIVES: Bronchioloalveolar carcinoma is a primary lung neoplasm of variable histopathologic, radiologic, and clinical expression. There are three cell types described in bronchioloalveolar carcinoma: Clara cells, mucin-producing cells, and alveolar type II epithelial cells. It is unclear whether these three tumor cell types are associated with a specific radiologic presentation and clinical course. In this study, we investigated whether tumor cell type, identified by transmission electron microscopy, correlated with a specific radiologic pattern, and whether tumor cell type or radiologic presentation correlated with the patient's clinical course and outcome. DESIGN: Transmission electron microscopy was used to restudy tissue blocks from the original surgical histopathologic specimens in 54 patients with primary bronchioloalveolar carcinoma diagnosed over a 10-year period (1980 to 1990). The pretreatment radiographs were reviewed in each case, and the first chest radiograph obtained at the time of the discovery of the tumor in each patient was compared with the results of the ultrastructural study. The medical records of each patient were examined to obtain pertinent radiologic, clinical, and patient outcome information. MEASUREMENT AND RESULTS: There were 32 Clara cell tumors, 10 mucin-producing cell tumors, and 1 alveolar type II epithelial cell tumor in this series. Eleven additional tumors had mixtures of two or more cell types. No statistically significant relationship was detected between tumor cell type and radiologic presentation or patient mortality pattern. There was increased mortality among patients who presented radiologically with segmental, lobar, multifocal, or diffuse disease compared with those patients exhibiting a solitary pulmonary nodule at presentation. CONCLUSION: Radiologic presentation, rather than tumor cell type, provides prognostic information that aids in predicting patient outcome.

Cytodifferentiation of atypical adenomatous hyperplasia and bronchioloalveolar lung carcinoma: immunohistochemical and ultrastructural studies.

We used immunohistochemistry and electron microscopy to evaluate the differentiation of cells comprising atypical adenomatous hyperplasia (AAH; n = 26), early bronchioloalveolar lung carcinoma (BAC; n = 11), and overt BAC (n = 16), which are assumed to constitute a continuous spectrum of developmental steps of BAC. Surfactant apoprotein (SAP), a marker for type 2 alveolar cells, was expressed in cells from all the lesions of AAH, early BAC, and overt BAC. However, the proportion of SAP-positive cells decreased and their distribution became more heterogeneous with advancing lesion grade. Urine protein 1, which is identical to the Clara cell-specific 10 kDa protein, was expressed in 70% of overt BAC, whereas only 20% of early BAC showed weak reactivity and none of AAH lesions showed any reactivity at all. Ultrastructurally, type 2 alveolar cell differentiation was predominant among cells from AAH and early BAC. Our results suggest that precursor cells of BAC differentiate predominantly towards type 2 alveolar cells. Cells comprising overt BAC retain this differentiation phenotype, but to a reduced extent. In contrast, concomitantly with progression, cells with Clara cell differentiation emerge and their proportion increases. Such phenotypic changes may reflect metaplasia occurring in tumour cells during the development of BAC.

Morphology of spontaneous and induced tumors in the bronchiolo-alveolar region of F344 rats.

The morphology of spontaneous and chemically-induced metastasizing carcinomas and adenomas in the bronchiolo-alveolar region of F-344 rats was studied. Histologically, the tumors were tubulo-papillary. Ultra-structurally, they consisted of cells which formed and secreted osmiophilic lamellated inclusion bodies, a marker of alveolar type II cells. Mitotic tumor cells also demonstrated such bodies. No cells of bronchial or bronchiolar origin were found in the tumors. We conclude that in F344 rats, lung tumors located in the bronchioloalveolar region consist of alveolar type II cells exclusively and are, therefore, alveolar cell adenomas and carcinomas, respectively.

Angiogenic nature of the "intravascular bronchioloalveolar tumor" of the lung: an electron microscopic study.

An intravascular bronchioloalveolar tumor of lung (IVBAT) was studied with electron microscopy. Based on ultrastructural evidence and information obtained from the literature, we propose the following: (1) IVBAT is a true pulmonary neoplasm with distinctive morphologic features; (2) it consists of cells with endothelial characteristics and is probably derived from multipotential mesenchymal reserve cells; (3) it is not related to the typical bronchioloalveolar tumor of lung; (4) a more appropriate designation for this unusual pulmonary neoplasm is "sclerosing angiogenic tumor."

Ultrastructural comparison of "alveolar" and "solid" areas in bronchioloalveolar carcinoma.

The purpose of this study was to compare the ultrastructural features of bronchioloalveolar carcinomas, contrasting the well-differentiated alveolar component and the poorly-differentiated solid component in the same tumor. We studied 7 cases of non-mucinous bronchioloalveolar carcinomas by electron microscopy. Two of these cases showed lamellar bodies in both the alveolar and solid components and the remaining 5 cases revealed Clara cell granules in both components. We conclude that the neoplastic cells in bronchioloalveolar carcinoma retain their ultrastructural phenotypes after becoming invasive carcinoma with loss of alveolar differentiation.

Metastatic adenocarcinoma of unknown primary site: diagnostic electron microscopy to determine the site of tumor origin.

Poorly differentiated malignant tumors and metastatic adenocarcinomas have been studied by electron microscopy. Rapid ultrastructural analysis allows the accurate diagnosis of the cell of tumor origin to be reported in conjunction with the routine surgical signout of paraffin sections. The identification of specialized intracellular structures is useful for determining the site of origin of metastatic tumors. Particularly useful in this material was the presence of lamellar (surfactant) bodies, typical of alveolar cell carcinoma of the lung, as well as the presence of apical terminal webs, diagnostic of gut epithelial cells.

Ultrastructural findings in metastatic bronchioloalveolar carcinoma.

This study was prompted by the recent revision of the definition of bronchioloalveolar carcinoma (BAC) that defines BAC, light microscopically, as a non-invasive carcinoma. Doubt has been raised whether BACs retain certain specific microscopic features after becoming invasive or metastatic. We studied 7 cases of metastatic, non-mucinous BAC by electron microscopy. Of these cases, 5 showed Clara cell granules and 1 revealed lamellar bodies. The remaining case did not show ultrastructural features of BAC. These findings suggest that most BACs retain some of their ultrastructural features after becoming metastatic neoplasms.

The concept of bronchioloalveolar cell adenocarcinoma: redefinition, a critique of the 1999 WHO classification, and an ultrastructural analysis of 155 cases.

Bronchioloalveolar cell adenocarcinoma (BACA) is bronchioloalveolar because (1) it arises in bronchioles and alveoli and (2) differentiates into bronchiolar and alveolar cells. Every entity possesses unique characteristics that separate it from other entities. The unique characteristic of BACA is its cell type. Lepidic growth is a clue to the cell type and, even though present in the vast majority, is not unique or absolutely essential. Because of the algebraic nature of concepts, the degree of differentiation, the extent of lepidic growth, and the degree of stromal desmoplasia cannot be used as definitional requirements. Likewise, in malignant tumors, absence of stromal invasion cannot be required. An epistemologically valid definition of BACA is proposed and a study of 155 cases defined this way and examined ultrastructurally is presented.

Bronchiolar-alveolar carcinoma in a cow.

Bronchiolar-alveolar carcinoma was observed in the lung of an 8-year-old Holstein cow. Grossly, the lung contained multiple tumour masses, which were solid, yellowish-white in colour, and firm in consistency. These tumours also occurred in the liver, pancreas, uterus and lymph nodes in the thoracic, abdominal and pelvic cavities. Histologically, the masses were composed of abundant fibrous stroma and proliferating atypical cuboidal epithelial cells, occasionally forming glandular structures. Electron microscopy revealed that the neoplastic cells had microvilli and lamellar bodies in the cytoplasm, suggesting that they originated from immature respiratory epithelial cells differentiating towards either Clara cells or type II pneumocytes.

Ultrastructure and origin of adenocarcinomas detected in the lungs of three cows.

Three types of bovine adenocarcinoma were found in the lungs of 3 cows. Case 1 was a well differentiated adenocarcinoma with mucin granules and microvilli with core filaments seen ultrastructurally. In Case 2, the neoplastic tissue showed a sarcoma-like growth with scattered tubular structures. Many cilia were observed in the tubular structures and a few cilia were found in the anaplastic tissues. Case 3 had epithelial and undifferentiated tissues. A few mucin granules and cilia were observed in the tumours in both lung and kidney. The relationships between these neoplastic cells and bronchial epithelial cells are discussed.