Stromal Elements for Tumor Diagnosis: A Brief Review of Diagnostic Electron Microscopic Features

Tumor diagnosis mainly depends on the appearance of the tumor cells in recapitulating the appearance of primordial cells from which they arise. However, certain tumors may present with specific stromal changes that may assist/enhance the diagnosis. In this presentation, diagnostic stromal features have been reviewed. The cytoplasm is enclosed by a unit membrane, which serves as a barrier to, as well as an interface with, surrounding structures. Epithelial cells usually show characteristic basal–apical orientation. In mesenchymal tissue, different types of interface can be found in different types of mesenchymal tissue. External lamina can be defined as an anatomic structure, which encloses anatomic functional units. In epithelial tissue, cells in a functional unit are enclosed within a well-defined external lamina (EL). In malignant epithelial tumors, EL can become increasingly indistinct as tumors become less differentiated, and one has to look for it diligently. Within the external lamina, epithelial cells are closely packed with closely apposed cell membranes and cell attachment junctions. In contrast to epithelial tissue, mesenchymal tissue is usually characterized by the stromal elements they produce. Individual cells are embedded in the stroma, and individual mesenchymal cells represent the functional unit. Vascular endothelial cells are an exception since their relationship to stroma resembles to that of epithelial cells. Thus, tumors deriving from mesenchymal cells known to have external lamina such as muscle cells and Schwann cells tend to show total enclosure of cells by external lamina. In malignant muscle tumors, external lamina production can be focally present and found only by diligent search. In Schwann cell tumors, the presence of EL is prominent in low-grade tumors and more irregular and variable in malignant tumors. In the latter, stromal aggregation of scrolls of external lamina can be characteristic. Similar features are seen in ossifying fibromyxoid tumors. Fibronexus junctions (composed of extracellular fibronectin fillements linking intracellular 5-nm filaments) is claimed to be typical of myofbroblasts. Finding them in spindle cell tumors justifies a diagnosis of myofibroblastomas. There have been several stromal changes diagnostic for certain tumors found only by electron microscopy. Fibrous long-spaced collagen (known as Luse bodies) is diagnostic for peripheral nerve sheath tumors, but they can rarely be found in other tumors. Luse bodies usually appear as focally as crystallized aggregates apart from the regular collagenous interstitial stroma. They should be distinguished from other nonspecific long-spaced collagen changes. The changes are diffusely stromal in contrast to Luse bodies. Spiny collagen and amianthoid fibers are interesting collagen fibrils and their diagnostic value is questionable. Skeinoid fibers (SF) are short-spaced collagen of 41- to 45-nm banding so-named because of their peculiar appearance by electron microscopy simulating skeins of yarn. They were originally described in neurogenic tumors and small intestinal stromal tumors with features of gastrointestinal autonomic nerve tumors (GANT). Although there have been a few sporadic case reports of the presence of skeinoid fibers in nonneurogenic tumors, the frequent presence of SF in spindle cell tumors signifies their neurogenic nature in this authors’ experience. An exception to this is that SF can be a constant element of rare ciliary body tumors known as ciliary mesectodermal leiomyomas, in which tumor cells show some resemblance to smooth muscle as well as Schwann cells. In addition to SF, several other types of peculiar crystallized collagen were observed in GANT tumors, particularly those with multiple tumor syndromes such as neurofibromatosis and Carney's triad. They simulate the appearance of railroad tracks or centrosomes. The reason for this is not known. The authors speculate that such collagen crystallization may be caused by genetic alterations involving collagenosis. Further studies will be necessary to clarify their pathogenesis. Another peculiar stromal change is electron-dense stromal filamentous aggregates with extra-long banding of > 250-nm periodicity previously described in Ewing sarcomas. This stromal change simulating a tiger skin pattern is also seen in primitive neuroectodermal tumors and malignant melanomas. In view of continually new discoveries of stromal changes that can be used for the differential diagnosis of tumors, the importance of close evaluation of stromal elements of tumors, and diligent application of electron microscopy in tumor diagnosis cannot be overemphasized.     

Inmumogold Localization of Actin and Cytokeratin Filaments in Myoepithelium

Myoepithelial cells of salivary gland are uniquely specialized cells; their function is unclear, but the considerable complement of muscle-specific actin suggests contractility is one function. By routine transmission electron microscopy myofilament visualization is variable. Some myoepithelial cells appear to have limited and only focal aggregates of myofilaments, while others seem to have readily appreciated myofilaments within a longitudinally oriented cytoplasmic zone at the basal portion of the cell. However, immunogold electron microscopy using the anti-muscle-specific actin antibody, HHF35, while indicating a basal distribution for the muscle-isoform of actin in a platelike fashion in certain myoepithelial cells, also reveals that others associated with both intercalated ducts and acini have a more generalized distribution of myofilaments throughout the cytoplasm. Actin was also noted within tonofilaments and double immunogold labeling using both the HHF35 and AE1/AE3 (anticytokeratins) antibodies confirmed the variable interrelationship of these two filaments. Within any one myoepithelial cell, actin and cytokeratins might colocalize in some areas of the cytoplasm containing filaments, but not in adjacent zones. These results suggest that intermediate filaments and myofilaments are complexly organized in myoepithelial cells, and that quantitative and qualitative differences exist in the expression and distribution of intermediate filaments and myofilaments. These cells are likely structurally, if not functionally, heterogeneous of Human Parotid Salivary Gland     

Inmumogold Localization of Actin and Cytokeratin Filaments in Myoepithelium

Myoepithelial cells of salivary gland are uniquely specialized cells; their function is unclear, but the considerable complement of muscle-specific actin suggests contractility is one function. By routine transmission electron microscopy myofilament visualization is variable. Some myoepithelial cells appear to have limited and only focal aggregates of myofilaments, while others seem to have readily appreciated myofilaments within a longitudinally oriented cytoplasmic zone at the basal portion of the cell. However, immunogold electron microscopy using the anti-muscle-specific actin antibody, HHF35, while indicating a basal distribution for the muscle-isoform of actin in a platelike fashion in certain myoepithelial cells, also reveals that others associated with both intercalated ducts and acini have a more generalized distribution of myofilaments throughout the cytoplasm. Actin was also noted within tonofilaments and double immunogold labeling using both the HHF35 and AE1/AE3 (anticytokeratins) antibodies confirmed the variable interrelationship of these two filaments. Within any one myoepithelial cell, actin and cytokeratins might colocalize in some areas of the cytoplasm containing filaments, but not in adjacent zones. These results suggest that intermediate filaments and myofilaments are complexly organized in myoepithelial cells, and that quantitative and qualitative differences exist in the expression and distribution of intermediate filaments and myofilaments. These cells are likely structurally, if not functionally, heterogeneous of Human Parotid Salivary Gland     

Meningioma of Lung: First Report with Light and Electron Microscopic Findings

This is the first report of a primary meningioma of the lung. The lesion was present at least 4 years prior to its operative removal. The 59-year-old patient is still healthy 2-1/2 years after operation. All examinations, including computed tomography, failed to detect another primary tumor. Light and electron microscopic findings are identical to those in endotheliomatous meningioma. The relations to the so-called minute pulmonary chemodectomas and the probable histogenesis are discussed.     

Gastric Duplication Cyst: Electron Microscopic and Immunohistochemical Study

The lining of a gastric duplication cyst was examined ultrastructurally and immunohistochemically. The cyst lining displayed the range of differentiation seen in normal fundic mucosa.     

Meningioma of Lung: First Report with Light and Electron Microscopic Findings

This is the first report of a primary meningioma of the lung. The lesion was present at least 4 years prior to its operative removal. The 59-year-old patient is still healthy 2–1/2 years after operation. All examinations, including computed tomography, failed to detect another primary tumor. Light and electron microscopic findings are identical to those in endotheliomatous meningioma. The relations to the so-called minute pulmonary chemodectomas and the probable histogenesis are discussed.     

Gastric Duplication Cyst: Electron Microscopic and Immunohistochemical Study

The lining of a gastric duplication cyst was examined ultrastructurally and immunohistochemically. The cyst lining displayed the range of differentiation seen in normal fundic mucosa.     

Electron Microscopic and Immunoelectron Microscopic Demonstration of Pancreatic Polypeptide Cells in Glucagonoma: Colocalization of Pancreatic Peptide and Glucagon in Single Secretory Granules

We describe a case of pancreatic tumor in a 65-year-old woman with typical glucagonoma syndrome. Plasma glucagon (GL) and pancreatic polypeptide (PP) were markedly elevated up to 1404 and 1 200 pg/ml, respectively. Histologic examination of the metastatic tumors in liver and lymph nodes showed endocrine-type tumors composed of GL-positive cells some of which coexpressed PP immunoreactivity. Electron microscopy revealed the tumor cells with single-type secretory granules similar to normal A cell granules. Double immunogold staining demonstrated both GL and PP immuno-reactivities in the same secretory granules. Biologic and diagnostic significance of coexpression of PP and GL in a single secretory granules of pancreatic endocrine tumors is discussed briefly.     

Nasal Blastoma: A Light and Electron Microscopic Study

The first light and electron microscopic study of a nasal blastoma is reported. Analogous to a pulmonary blastoma, the tumor is composed of well-differentiated squamous and glandular epithelial elements surrounded by a spindle cell stroma. The spindle stromal cell is a myofibroblast. Eighteen months after complete surgical removal of the tumor and radiation therapy, the patient is clinically free of disease.     

扫描电镜观察肿瘤细胞受攻击过程中的形态变化

本文以扫描电镜观察了Ｂ淋巴细胞白血病瘤系细胞（Ｒａｊｉ细胞）在遭受淋巴因子激活的杀伤细胞（ＬＡＫ细胞）攻击时所表现的超微结构外形改变。结果发现ＬＡＫ细胞不仅可主动接近瘤细胞，并在该处出现胞吐分泌象；瘤细胞的主要改变则在与ＬＡＫ细胞的接触处，渐次形成窦穴，甚至遭受该细胞的穿凿性攻击致胞体受损，终而导致死亡解体。研究中还发现ＬＡＫ细胞也有相应地生理性耗损现象。     

Localization of E-Cadherin adhesion molecules in human gingiva and gingival carcinoma

Immunohistochemical investigations were carried out on the localization and expression of the Ca²⁺-dependent intercellular adhesion molecule E-cadherin in human gingiva and gingival carcinoma. Although E-cadherin did not appear in the parakeratinized layer of either clinically healthy or inflamed gingiva, it did appear strongly in the prickle layer and somewhat more weakly in the basal layer. Immunogold particles reactive to anti-E-cadherin monoclonal antibody in the electron microscopic findings were localized only in the vicinity of the desmosomes of the prickle and basal layers. In the case of gingival carcinoma, although E-cadherin was strongly expressed in the cells surrounding the keratinized region in the cancer nests, the expression decreased towards the marginal portion of the cancer nests. The distribution of E-cadherin in these cells may be dependent on the condition of the cancer cells that are potentially invasive. These findings suggest that cells of the parakeratinized layer of gingiva and cells of the marginal portion of the gingival carcinoma nests may easily detach or invade. In addition, the findings suggest that the gingival carcinoma used in this study tended to be invasive.     

大肠癌移行粘膜扫描电镜观察及其意义的探讨

25例大肠癌移行粘膜的扫描电镜与光镜观察显示有不同形式改变。电镜发现所有病例移行粘膜均有明显异常改变,距癌灶2cm以内异常者占88.0%(22/25)。而光镜下该区无非典型性增生,仅见杯状细胞数量及体积增加,肠腺凹形态有不同程度改变。因此,移行粘膜的扫描电镜改要虽然不能确切反映肠粘膜内部组织学变化性质,但可提供异常三维结构的粘膜范围,为大肠癌癌旁粘膜切除范围的选择提供参考数据。     

Subcellular Localization of YKL-40 in Normal and Malignant Epithelial Cells of the Breast

YKL-40 is a new prognostic biomarker in cancer. The biological function is only poorly understood. This study aimed at determining the subcellular localization of YKL-40, using immunogold labeling, in normal epithelial cells and in malignant tumor cells of the breast by immunoelectron microscopy. YKL-40 protein expression was redistributed in carcinoma versus normal glandular tissue of the breast. A reduced expression of YKL-40 in relation to intermediate filaments and desmosomes was found in tumor cells. Changes in YKL-40 expression suggest that the function of YKL-40 in cells of epithelial origin may be related to cell motility and cell–cell adhesion, features associated with invasion and migration potential of tumor cells.     

Techniques a Simple Method for the Collection of Cells from Cerebrospinal Fluid for Electron Microscopy

A simple membrane filter technique permits the collection of cells from cerebrospinal fluid for electron microscopy. The method is universally applicable for the concentration of small number of cells from free-floating cell suspensions and has several advantages: (1) Only a small fluid sample (1 ml) is needed. (2) Excellent cell preservation is obtainable. (3) High cell recovery rates are achieved. (4) Quantitative classification of cell types is possible.     

Ultrastructural Changes in Smooth Muscle Cells of the Small Intestine in Suckling Rabbits with Experimental Cholera

Ultrastructural study of the small intestine in suckling rabbits with experimental cholera revealed involvement of the inner and outer smooth muscle layers into the pathological process. Smooth muscle cells were characterized by vacuolar and fatty degeneration and focal colliquative necrosis. Apoptosis played little role in gastrointestinal motility disturbances. The presence of considerable amounts of fluid in intestinal loops reflects peristaltic dysfunction due to generalized damage to smooth muscle cells.     

Techniques a Simple Method for the Collection of Cells from Cerebrospinal Fluid for Electron Microscopy

A simple membrane filter technique permits the collection of cells from cerebrospinal fluid for electron microscopy. The method is universally applicable for the concentration of small number of cells from free-floating cell suspensions and has several advantages: (1) Only a small fluid sample (1 ml) is needed. (2) Excellent cell preservation is obtainable. (3) High cell recovery rates are achieved. (4) Quantitative classification of cell types is possible.     

Mucinous Colorectal Adenocarcinoma with Signet-Ring Cells: Immunohistochemical and Ultrastructural Study

A primary mucinous colorectal adenocarcinoma tissue with signet-ring cells, as revealed after histological evaluation, was examined ultrastructurally. The authors also analyzed the immunohistochemical data of the tissue for serotonin, vasoactive intestinal polypeptide (VIP), bombesin, somatostatin, and glucagon, using the peroxidase anti-peroxidase (PAP) method and the immunogold labeling method for light and electron microscope, respectively. Electron microscopically mucinous adenocarcinoma was characterized by the formation of small lumen. Adenocarcinoma cells were full of mucous granules of varying electron density, providing a good environment for the tumor cells to grow. They also exhibited a significant loss of microvilli and intracytoplasmic junctions, which could allow the cells to disseminate. Signet-ring cells were located in the basal site of the ducts or in the lamina propria and appeared neoplastic, with mucin accumulation intracellularly and an eccentric crescent-shaped nucleus. The cytoplasmic organelles were decreased and at the periphery of the cell. The PAP method demonstrated that these cells were strongly positive for bombesin and also positive for vasointestinal polypeptide (VIP). The immunogold method detected bombesin immunoreactivity in the vacuoles as well as in other cytoplasmic membranes, whereas VIP was localized mainly in the plasma membrane. The location of signet-ring cells combined with the immunoreactivity for bombesin and VIP indicated that signet-ring cells were of neuroendocrine origin and probably dedifferentiated enterochromaffin-like endocrine cells. These findings have implications for understanding the biological behavior of these composite malignant tumors and could help in the knowledge of the origin of signet-ring cells.     

The Evolving Concept of Renal Neoplasia: Impact of Emerging Molecular and Electron Microscopic Studies

The classification of renal tumors has evolved from one that initially encompassed only 2 types of tumors, i.e., clear and granular cell carcinomas, to the markedly expanded recent classification that incorporates new entities, some of which are primarily defined by specific molecular abnormalities. Despite these advances, a single tumor category, clear cell carcinoma, still incorporates the majority (∼70%) of renal tumors. It is, however, postulated that this single category is likely to encompass several different tumor types that are, at present, undifferentiated. Electron microscopic studies have been pivotal in defining the spectrum of oncocytoma-chromophobe renal cell carcinoma. Cytoplasmic eosinophilia found in some renal cell carcinomas currently classified as clear cell type is under intense study. Tumors that have recently emerged from this group include tumors with translocations involving chromosome Xp11.2, carcinomas associated with neuroblastoma and epithelioid angiomyolipoma. The spectrum of renal tumors seen in younger patients is wider than among older patients, with rare and unusual tumors being more likely seen in younger patients. The author concludes that although the routine application of electron microscopy to kidney tumor diagnosis may not be practical, systematic ultrastructural studies of these tumors may aid in the definition of new entities.     

The Evolving Concept of Renal Neoplasia: Impact of Emerging Molecular and Electron Microscopic Studies

The classification of renal tumors has evolved from one that initially encompassed only 2 types of tumors, i.e., clear and granular cell carcinomas, to the markedly expanded recent classification that incorporates new entities, some of which are primarily defined by specific molecular abnormalities. Despite these advances, a single tumor category, clear cell carcinoma, still incorporates the majority (～70%) of renal tumors. It is, however, postulated that this single category is likely to encompass several different tumor types that are, at present, undifferentiated. Electron microscopic studies have been pivotal in defining the spectrum of oncocytoma–chromophobe renal cell carcinoma. Cytoplasmic eosinophilia found in some renal cell carcinomas currently classified as clear cell type is under intense study. Tumors that have recently emerged from this group include tumors with translocations involving chromosome Xp11.2, carcinomas associated with neuroblastoma and epithelioid angiomyolipoma. The spectrum of renal tumors seen in younger patients is wider than among older patients, with rare and unusual tumors being more likely seen in younger patients. The author concludes that although the routine application of electron microscopy to kidney tumor diagnosis may not be practical, systematic ultrastructural studies of these tumors may aid in the definition of new entities.