Non-Hodgkin's lymphoma classification: ultrastructural morphometric studies for the quantification of nuclear compartments in situ

Nuclear morphometry and texture analysis of B-cell non-Hodgkin lymphoma: utility in subclassification on cytosmears

Non-Hodgkin lymphoma (NHL) is a heterogeneous group of lymphoid neoplasms and accurate subclassification is an essential prerequisite for proper management of patients. This study was aimed at evaluating the utility of nuclear morphometry and textural features on cytology smears to classify the cases of NHL on aspiration cytology. Fine needle aspiration smears of 50 cases of B-cell NHL were included. Various morphometric and texture parameters were obtained by manually tracing the nuclei on digitized images in each case and discriminant analysis performed using various features taken individually as well as all together. The percentage of cells correctly classified to a particular NHL subtype using the discriminant functions so obtained was noted.Our results show that discriminant analysis done on size parameters could correctly classify a greater number of cells than on shape parameters (36.4% vs. 21.2%, respectively). Texture parameters based on single pixel values (first order texture) were inferior (42.8%) to those based on pair of pixels (58.7%) in subtyping of cells. Discriminant analysis based on color parameters was more effective (61.9%) as compared to rest of the morphometric and textural parameters. Using all the morphometric and textural parameters together, 83.3% of cells could be correctly classified to a particular NHL subtype.The present study, perhaps the first study of detailed morphometric analysis on cytosmears, shows that satisfactory classification of NHL on aspiration cytology is possible using nuclear morphometry and textural parameters considered together. These results are promising for further studies on this subject and development of automated cytodiagnosis.

Nuclear localization of cytokeratin 8 and the O-linked N-acetylglucosamine-containing epitope H in epithelial cells of infiltrating ductal breast carcinomas: a combination of immunogold and EDTA regressive staining methods

In a previous study, the authors have shown cytokeratin 8 (CK8) and epitope H ultrastructural localization in breast cancer cell nuclei. Epitope H contains an O-linked N-acetylglucosamine (O-GlcNAc) residue in a specific conformation and/or environment recognized by monoclonal antibody H. In this study, double immunogold labeling of CK8 and epitope H combined with the EDTA regressive staining method was applied in biopsy material from infiltrating ductal breast carcinomas and fibroadenomas, to localize both antigens in correlation to RNPs distribution in the nuclear subcompartments of cancer cells. CK8 and epitope H were localized mostly over condensed chromatin, whereas staining was weaker over interchromatin granule clusters and perichromatin fibers. These results revealed, the distribution of CK8 in the nucleus as MAR-binding protein, contributing in the organization of the nuclear DNA in the neoplastic cell, as well as the distribution of O-GlcNAc glycosylated polypeptides bearing the epitope H. The latter finding indicates that these polypeptides might play a significant role in the neoplastic behavior of breast cancer cells because they colocalize in the same nuclear subcompartments with proteins modified by O-GlcNAc, such as hnRNPs G and A1, RNA polymerase II, its transcription factors, and the oncogene product of c-myc. These proteins are known to participate in coordinated transcription/RNA processing events, contributing in the neoplastic behavior of breast cancer cells.

Proteins recognized by antibodies against isolated cytological heterochromatin from rat liver cells change their localization between cell species and between stages of mitosis (interphase vs metaphase)

Heterochromatin in the cell nucleus seems to concentrate various proteins, such as Drosophila heterochromatin protein 1, which maintain the repressed state of gene expression. However, it still remains obscure how protein composition related to chromatin structure is different between heterochromatin and euchromatin in interphase nuclei. We isolated cytological heterochromatin from sonicated interphase nuclei obtained from rat liver cells and prepared antisera against it. The dense heterochromatic bodies seen in the preparation of intact nuclei were duplicated in a relatively pure form during the preparation of heterochromatin. In the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, differences between the fractions of heterochromatin and euchromatin were noted by their protein composition. Isolated heterochromatin was then digested by DNase after partial digestion with trypsin and its dense structure changed to become highly sensitive to DNase. The prepared antibodies reacted with the heterochromatin region of rat liver cell nuclei and isolated cytological heterochromatin; however, they did not react with euchromatin. Using immunohistochemistry, the antibodies bound to each cell nucleus in all tissues observed; some cell types were distinguished by their differential stainability (e.g. staining in the cytoplasm). Staining of the mitotic cells showed that the proteins recognized by the antibodies were localized in the cytoplasm and, in part, on the chromosomes. Based on the results of molecular cloning from rat liver cDNA library using the antibodies as a probe, it seemed that the antibodies mainly recognized two proteins similar to arginase and general vesicular transport factor p115, respectively. The results obtained from these experiments reveal that some proteins located in the heterochromatin of interphase liver cell nuclei seem to play important roles in condensing a portion of the chromatin structure during interphase and suggest that proteins composing heterochromatin might be changed according to cell types or the stage of the cell cycle.

Morphometric analysis of bovine lymphomas classified according to the National Cancer Institute Working Formulation

The National Cancer Institute Working Formulation (NCI-WF) for the subjective classification of human non-Hodgkin's lymphoma is readily applicable to the classification of bovine lymphomas. Forty-nine cases of bovine lymphoma were analysed morphometrically to see if nuclear size and cleavage were distributed continuously or discretely between different NCI-WF tumour cell types. The mean nuclear area (+/- standard error of the mean, SE) was significantly greater (P < 10(-6)) in cells from the different types of diffuse large-cell lymphoma than in cells from the different types of small-cell lymphoma (42.91 +/- 1.21 micron 2 vs 19.33 +/- 1.08 micron 2, respectively); there was no overlap between the two groups. The mean nuclear are (+/- SE) of cells from diffuse large-cell lymphomas was significantly greater (P < 10(-4)) than that of cells from small non-cleaved lymphomas (42.74 +/- 1.72 micron 2 vs 27.54 +/- 1.08 micron 2, respectively), and there was again no overlap between the two groups; these two cell types are difficult to distinguish by any criteria other than size. Additionally, the cell-to-cell variability in nuclear area within a given tumour was significantly greater (P < 0.001) for the diffuse large-cell type than for the small non-cleaved cell type. The mean nuclear form factor (+/- SE) and mean nuclear contour indices (+/- SE) of the diffuse large cleaved cell type (0.53 +/- 0.02 and 5.08 +/- 0.11, respectively) were significantly different (P < 0.01 to 10(-6)) from the same parameters in the diffuse large-cell type (0.82 +/- 0.01 and 3.94 +/- 0.04, respectively). Some of the major criteria of the NCI-WF used subjectively to discriminate between bovine lymphoma cell types were supported by morphometric measurements. The magnitude of the differences in nuclear morphological characteristics between bovine lymphoma cell types was such that there was no overlap.

Clinical and biological applications of image analysis in non-Hodgkin's lymphomas

The technical procedures and the main applications of image analysis in non-Hodgkin's lymphoma pathology have been described by reviewing the pertinent literature. With the advent of sophisticated computer-based technology, the possibility of objectively evaluating cell morphology, in situ marker expression, DNA indexes, and complex structural features may become a relevant part of the pathologist's expertise.

Morphometric study of primary cutaneous germinal center cell lymphomas

BACKGROUND

Primary cutaneous germinal center cell lymphomas (PCGCCL) are B-cell neoplasias; most are mixed cell type, composed of small and large cleaved cells and large noncleaved cells (centrocytes and centroblasts). Because of the significant pleomorphism of the cells, which ranged in size from small elements with indented nuclei to larger ones with multilobulated vesiculous nuclei, histopathologic examination of PCGCCL of mixed cell type has the worst degree of histologic interobserver reproducibility.

METHODS

In this study, the authors determined whether the light microscopic morphologic classification criteria applied in quantifying cleaved and noncleaved cells in these lymphomas are substantiated by morphometric analysis and have good reproducibility in differentiating the various cell subsets. They used an image analyzer (IBAS 2000, Zeiss Kontron, Munich, Germany) to study 17 centroblastic/centrocytic and centroblastic follicular and/or diffuse primary cutaneous lymphomas.

RESULTS

The data obtained showed morphometric differences between the follicular and diffuse patterns of neoplastic cells. In follicular neoplasms, the cells tend to be smaller, more cleaved, and more monomorphic than those observed in the diffuse forms. In all the follicular and diffuse cases, the authors observed a unimodal population with a wide peak composed of cells with intermediate morphometric features that cannot be labeled properly.

CONCLUSIONS

These data underline the considerable overlap of nuclear parameters of lymphocytes between the subtypes of cells in cutaneous mixed small and large cell lymphoma, making the Kiel classification and Working Formulation unsuitable for this kind of neoplasia and supporting revision of classification criteria in cutaneous germinal center cell lymphomas.

Microanalytical techniques and image analysis in the evaluation of immunogold-labeled specimens at the ultrastructural level

Energy-dispersive X-ray microanalysis (EDX) interfaced to a scanning/transmission electron microscope allows direct visualization and photographing of structures analyzed under the electron beam. EDX can perform a point-by-point analysis as it searches for the ion whose X-ray window the computer has been instructed to localize. This technique has been utilized to define ultrastructural immunogold labeling patterns. Once a specimen is immunolabeled with gold, microanalytical techniques can identify the quantity and distribution of detected and labeled antigenic epitopes. Microanalytical techniques add a new objective dimension to ultrastructural gold labeling procedures. Quantitative microanalysis of the gold-labeled antigenic sites provides a way of assessing the specificity of the reactions and permits comparison of the degree of expression of antigenic determinants in different specimens. Image processing allows visual representation of the immunolabeling results. Furthermore, statistical analysis of a large number of parameters is also possible with the digitized images collected. Ultrastructural microanalytical techniques represent a new, unexplored application that may play an important role in the future of ultrastructural pathology and immunologic evaluation of diseased tissues.

Ultrastructural morphometry and the control of lymphocyte nuclear size in non-Hodgkin lymphoma: a review

Morphologic features, particularly nuclear characteristics, continue to be a major factor in the classification of the subtypes of non-Hodgkin lymphoma (NHL). Information is limited or nonexistent, however, concerning the mechanisms responsible for nuclear appearance. This is particularly true for nuclear size. In determining which of the nuclear compartments--condensed chromatin or the interchromatinic (euchromatin or nuclear matrix) region--is responsible for nuclear size, ultrastructural morphometric analysis has been a useful tool. Linear regression analysis has been used to compare, in turn, condensed chromatin area (CCA) and interchromatinic area (ICA) against nuclear area (NA). Whether in normal or neoplastic lymphocytes, correlation coefficients are moderately good when CCA is matched against NA, but CCA is only a weak predictor of NA. In contrast, correlation coefficients are remarkably high for ICA compared to NA, and ICA predicts NA to the degree of 94% to 97%. This holds true for all NHLs tested and for reactive hyperplasias. Despite abnormalities in lymphocyte nuclear size in NHL, the size of any nucleus is controlled by the amount of interchromatinic material to an exceptional degree. Even so, the mechanisms responsible for major changes in nuclear volume during transformation of normal lymphocytes are apparently altered in NHL. Morphometric analysis, ultrastructurally, can assist in understanding, testing, and defining diagnostic morphologic criteria in this disease.

Ultrastructural morphometry of human leucocytes in health and disease

In this review, the literature on ultrastructural morphometry of each of the main types of human blood leucocytes has been considered, together with the technical and numerical procedures essential for valid analysis. Quantitative data have been reported for these cell types in health and comparisons have been made with those in disease states. In monocytes, and in macrophages developing from them, subtle ultrastructural differences have been detected and quantitated in malignant lymphoma; as the mononuclear phagocytes were not themselves neoplastic, the changes may have related to defects in host defence. Change in the ultrastructural characteristics of leukaemic monoblasts have also been reported. Lymphocytes and malignant lymphoid cells have been extensively investigated: differences between different types and subsets have been shown to be present in both normal lymphocytes and their malignant counterparts in leukemias and lymphomas. Particular attention has been paid to morphometric assessment of nuclear shape and size in these disorders and to its possible value as a diagnostic tool. Granulocytes have so far been the subject of few morphometric studies, although in hypereosinophilic syndrome, cellular changes have been defined and have thrown light on the abnormal pattern of degranulation. There have also been scattered reports on the cells of acute myelogenous leukaemia. The use of computers and sophisticated statistical packages has greatly facilitated the application of multiple comparison procedures and has permitted discriminant analysis to be carried out where appropriate. This review shows that ultrastructural morphometry of leucocytes will have an increasing application in clinical pathology.

Computer aided cytometry in high grade malignant non-Hodgkin's lymphomas and tonsils

The aim of the study is to establish quantitative cytological criteria for reliable diagnoses in high grade malignant non-Hodgkin's lymphomas (NHL). For this purpose Pappenheim-stained cytologic imprints from 15 cases of high grade malignant NHL and ten cases of chronic tonsillitis have been analysed using a TV-microscope system, high resolution color scanning (13.3 pixel/microns), and image processing on a computer. The highly reliable computer-extracted cell features can be used to discriminate the different cell types of malignant NHL. Because of a considerable overlap, no feature on its own is sufficient to discriminate all the different cells. Only multivariate analysis of a suitable combination of features allows reliable discrimination. The results show that the different cells defined by subjective morphological criteria in the Kiel-classification of malignant NHL also form distinctive subpopulations with regard to their objective mathematical cell features and show distinctive differences when compared with their benign counterparts derived from reactive lymphatic tissue.

Ultrastructural morphometric study of follicular center lymphocytes: I. Nuclear characteristics and the Lukes-Collins' concept

A combined ultrastructural and morphometric image analysis study was carried out on the nuclear profiles of follicular center and mantle zone lymphocytes of six cases of reactive hyperplasia in human lymph node biopsies. For accuracy of morphological observations and sampling at low magnifications, sections were mounted on formvar-covered slot grids. Measurements of nuclear profile features of small (untransformed) lymphocytes in mantle zones served as the standard for a supposed unimodal population in each case. Analysis of nuclear profile area values indicated that during lymphocyte transformation in follicular centers nuclei had a gradual and progressive increase in size and that the sampled nuclear profiles in both the mantle zone and follicular center were unimodal. Lymphocyte nuclear shape (contour index) was a more complex, and likely biologically independent, feature than nuclear area in both the mantle zone and follicular center. Nuclear profile contour indexes of mantle zone lymphocytes were more irregular than suspected and in some cases had mean values greater than those of follicular center lymphocytes. Furthermore, the frequency distribution of nuclear contour index was not normally distributed in either the follicular center or mantle zone due to the presence of a small proportion of highly irregularly shaped nuclear profiles in both sites. The results indicated that some premises of existing concepts of follicular center cells and the process of lymphocyte transformation in follicular centers were incorrect and should not be directly extrapolated to the nuclear profile characteristics in non-Hodgkin's lymphoma.

Movement of the X chromosome in epilepsy

The position of selected chromosomes was assessed in samples of normal and epileptic human cortex with biotinylated probes specific for individual chromosome domains. Optical sectioning provided a rapid method for three-dimensional resolution of in situ hybridization signals in interphase cells, and solid models were reconstructed from digitized images for detailed rotational studies. There was a dramatic repositioning of the X chromosome in neurons of both males and females in electrophysiologically defined seizure foci. Other chromosomes (1, 9, and Y) showed more subtle positional changes. Specifically altered nuclear patterns involving the X chromosome may become established and create the genetic memory for intractable seizure activity.

Morphologic studies of lymphocyte nuclei in follicular and diffuse mixed small- and large-cell (lymphocytic-histiocytic) lymphoma

Twelve examples of mixed small- and large-cell lymphoma (eight follicular, one follicular and diffuse, and three diffuse) were investigated morphometrically using plastic-embedded tissue in order to study nuclear characteristics of lymphocyte populations in this form of non-Hodgkin's lymphoma (NHL) and to test morphologic bases for current NHL classification systems. This study illustrates that there are many inaccuracies, illusions, and misconceptions in the morphologic criteria currently used to classify mixed small- and large-cell lymphoma. A principal finding was that lymphocyte nuclear profiles in mixed-cell lymphomas tend to be smaller in size (P less than .005) and more irregular in shape (P = .0001) than the morphologically similar counterparts in germinal centers of lymph nodes with reactive hyperplasia. Intercase comparison of mixed small- and large-cell lymphomas revealed a considerable range of mean nuclear area values, some of which were within the size range of normal, small lymphocytes. At the magnifications used for morphometric assessment, a high proportion of lymphocyte nuclear profiles had shallow invaginations, but only a limited number of profiles (4% to 14%) had deep (cleaved) indentations. Contrary to current definitions for this subtype of NHL, lymphocytes with "small" nuclei had the same proportion of the nuclear diameter occupied by nuclear invaginations as lymphocytes with "large" nuclei and, in fact, mean nuclear invagination depth was shallower in "small" nuclei than in "large" nuclei. Furthermore, regardless of whether it is nuclear area or shape that is evaluated, lymphocytes in mixed-cell lymphoma do not separate into two populations of small-cleaved and large noncleaved cells. Morphometry reveals that only four of the 12 examples of mixed small- and large-cell lymphoma had a proportion of the lymphocytes in the size range of fully transformed germinal center lymphocytes that exceeded 25%, and none of the cases approached 50% even though the population of lymphocyte nuclei appearing "transformed," and therefore "large," ranged from 28% to 57%. Such results indicate that the large, noncleaved and cleaved component, as seen in histologic sections of mixed small- and large-cell lymphoma, do not have nuclei of uniform size and many, in fact, are not actually large. The morphometric findings indicate reasons for the poor observer reproducibility in classifying this subtype of NHL.

Prognostic significance of differential cell counts in non-Hodgkin's lymphomas

The use of differential counting on H & E stained sections is proposed as a simple means to define low grade malignant and high grade malignant cytologic categories in non-Hodgkin's lymphomas. Differential counts were performed in lymphoma biopsies from 616 cases. In each biopsy we counted 100 lymphoma cells and classified each cell as belonging to a "small", "medium-sized", or "large" cell type. The results indicate the presence of two prognostically distinct cytologic categories: a low grade and a high grade malignant. Lymphomas with less than 10% "large" cells represented low grade malignant cytology. Included in this category were also the, mainly follicular, lymphomas with more then 70% "medium-sized" cells (up to about 25% "large" cells). In addition to the cytologic category, the architectural pattern is of major prognostic importance. We recommend the use of three prognostic categories in non-Hodgkin's lymphomas: I) Favourable architecture + favourable cytology. II) Unfavourable architecture + favourable cytology. III) Unfavourable cytology.

Application of quantifiable criteria in the Lukes and Collins classification of non-Hodgkin's lymphomas

Measurements of nuclear size and differential counts among six lymphoma cell types were performed on H & E stained sections. In differential counting, the definition of cell types was based on nuclear shape, chromatin pattern, and nucleoli. In a pilot study comprising 93 patients we found actual nuclear size inadequate for use in lymphoma classification. This was due to: 1. great overlap among cytological types; 2. no independent prognostic value of mean nuclear area; 3. contradictory terminology; the large cleaved type belonging to the small cell category (mean nuclear area below 40 microns2), and the small non-cleaved type belonging to the large cell category (mean nuclear area above 40 microns2). Differential counting--requiring about 10 min--was an easy way to meet the need for a more objective evaluation of the cellular composition in non-Hodgkin's lymphomas. Quantifiable criteria based on differential counts were applicable in subclassification of three T-cell and seven B-cell types with an intraobserver reproducibility of 80%. More than 25% "large" cell types in a differential count implied an unfavourable prognosis. In test material, using a semi-morphometric classification, a correct prognostic category was obtained in 92% of 461 lymphomas and correct sub-classification obtained in 68%.

Follicular center cell lymphoma. Morphologic data relating to observer reproducibility

Subjectivity and observer variation in non-Hodgkin's lymphoma continues to plague current classification schemes. It was thought important to assess objectively derived morphometric data to see if three categories of follicular center cell (FCC) lymphomas, follicular small cleaved cell, follicular mixed small cleaved and large cell, and diffuse and nodular large cell, actually fall into distinctly separate classes based on nuclear parameters. Mean nuclear area, contour index and invagination depth of neoplastic lymphocytes, and the percentage of invaginated and clefted nuclear profiles in each example of FCC lymphoma were evaluated by three different approaches. Results obtained from distribution of the morphometric data in scatter diagrams, calculation of the overlap index, and linear regression values, all revealed considerable (but variable) degrees of overlap between the three FCC subtypes regardless of the nuclear parameter employed. Where separation between FCC lymphomas was maximal, although still incomplete, there was no consistent correlation between the nuclear parameter and the pair of FCC lymphomas being compared. At least in terms of nuclear morphological features, non-Hodgkin's lymphomas of FCC type seem to represent a continuum of one disease process. The information provides a basis for understanding some reasons underlying the problem of observer variation in non-Hodgkin's lymphoma.