Biophysical characterization of normal T-lymphocytes and Sézary cells

High-Scatter Lymphocytes in the Blood of Erythrodermic Cutaneous T-Cell Lymphoma: Evidence for Large-Cell Transformation?

BACKGROUND

Erythrodermic cutaneous T-cell lymphoma consists of erythrodermic mycosis fungoides and Sézary syndrome. Previous studies have indicated that very large Sézary cells (> 14 μm diameter) or the presence of aneuploid cells in the blood might reflect large-cell transformation, with a corresponding poor prognosis.

PATIENTS AND METHODS

A retrospective study assessed data between June 1997 and April 2002 of 32 patients with erythrodermic cutaneous T-cell lymphoma, 4 patients with leukemic mycosis fungoides, and 19 patients with nonneoplastic inflammatory conditions who were referred for evaluation of possible cutaneous T-cell lymphoma. Data were studied by 2-parameter flow cytometry gated on the lymphocyte population.

RESULTS

High-scatter T lymphocytes (HSL) were detected in initial blood samples from 10 of 19 patients with Sézary syndrome, 1 of 13 patients with erythrodermic mycosis fungoides, and no patient with nonneoplastic inflammatory conditions. A significant correlation was found between HSL and very large Sézary cells and histopathologic evidence of large-cell transformation. Moreover, the presence of HSL suggests a poor prognosis even for patients with advanced disease.

CONCLUSION

We propose that HSL are often large transformed neoplastic Sézary cells that may be detected in patients with clinically unapparent large-cell transformation.

Gene expression in the cell cycle of human T lymphocytes: I. Predicted gene and protein networks

The key genes involved in the cell cycle of human T lymphocytes were identified by iterative searches of gene-related databases, as derived also from DNA microarray experimentation, revealing and predicting interactions between those genes, assigning scores to each of the genes according to numbers of interaction for each gene weighted by significance of each interaction, and finally applying several types of clustering algorithms to genes basing on the assigned scores. All clustering algorithms applied, both hierarchical and K-means, invariably selected the same six "leader" genes involved in controlling the cell cycle of human T lymphocytes. Relations of the six genes to experimental data describing switching between stages of cell cycle of human T lymphocytes are discussed.

Analytic morphology in clinical and experimental dermatology

During the past several years, quantitative morphology has gained increasing attention in diagnostic pathology and in certain research applications. In the field of dermatopathology, quantitative morphology has been applied to numerous problems, ranging from the interactive measurement of nuclear contours to fully automated, high-resolution image analysis of ultrastructural micrographs. Dermatologic applications are reviewed, and potential developments in the future are briefly outlined.

Prognostic significance of DNA cytometry in cutaneous malignant lymphomas

The current classification of cutaneous malignant lymphomas (ML) into low-grade and high-grade lymphomas was found to be of limited reproducibility and permitted only a rough prediction about outcome. With this in mind, the relationship between nuclear DNA content and both prognosis and histologic grading according to the Kiel classification was evaluated on Feulgen-stained imprint specimens. In all, 49 cases of malignant non-Hodgkin's lymphoma, primary of the skin or with an involvement of the skin as one of the first symptoms, were studied using a computerized high-resolution image analysis system. The 2c deviation index (2cDI), which reflects the variation of the nuclear DNA values around the normal diploid peak, was found to be the best prognostically relevant criterion. Using the 2cDI, a significant discrimination (P less than 0.001 in the U test) between low-grade and high-grade ML was achieved. The prognostic benefit of the 2cDI was well documented by a significant inverse correlation between the 2cDI and the period of time until the patients progressed at least into one higher stage or died of lymphoma (r equals -0.63, P less than 0.05). In addition, the 2cDI enabled prognosis of the course of disease. In the group with low 2cDI values (2cDI, less than 0.5), no progression of the disease was observed after 1 year. In the groups presenting with a 2cDI between 0.5 and 1.0 and higher than 1.0, a progression was found in 57% and 64% of the cases studied, respectively. In conclusion, these measurements indicate that the determination of DNA distribution patterns in imprint specimens allows a precise and objective prognostic evaluation of cutaneous ML.

Differentiation between lymphomas and pseudolymphomas of the skin by computerized DNA-image cytometry

The histologic and immunohistologic differential diagnosis between pseudolymphomas (PL) and malignant lymphomas (ML) of the skin can be difficult. Since DNA cytometry has been found to be of both diagnostic and prognostic value in various neoplasms, its ability to discriminate between ML and PL in Feulgen-stained imprints of 17 PL and 49 ML skin biopsies was examined by high-resolution image analysis. The reliability of the following algorithms of DNA distribution was evaluated: 1) 2cDI (2c-deviation index), which reflects the variation of the nuclear DNA values around the diploid DNA peak; 2) percentage of cells having a DNA value greater than or equal to 5c (5cER; 5c-exceeding rate); 3) percentage of cells presenting with a DNA value greater than or equal to 4c (4cER). A 2cDI of 0.1 was found to be the most reliable marker for the differentiation between PL and ML. On the basis of this feature, 16 of 17 cases of PL and 46 of 49 cases of ML were correctly classified. The sensitivity, specificity, and efficiency of this feature were 94%. A 5cER greater than or equal to 1% had a specificity of 100%, but the sensitivity was only 43%. For the 4cER, a sensitivity of 61% and a specificity of 94% were found. In conclusion, the calculation of the 2cDI and the 5cER based on high-resolution image analysis provided additional helpful diagnostic features, and therefore should be included as a diagnostic tool. If the 5cER is at least 1%, the diagnosis of a ML can be confirmed with a specificity of 100%.

DNA analysis by flow cytometry in cutaneous T-cell lymphomas

DNA histograms of skin and blood specimens from 64 patients with known or suspected cutaneous T-cell lymphoma (CTCL) have been examined and compared with normal blood mononuclear cells and skin biopsy samples from 50 patients with various benign cutaneous conditions (i.e. patch test infiltrates, eczema, psoriasis, lichen planus, atopic dermatitis) in an attempt to establish whether DNA measurements by flow cytometry may improve the early recognition of CTCL. The results indicate that right-skewed G0/G1 peaks are seen frequently in both benign disorders and known and suspected CTCL. Such peaks may reflect increased stainability of DNA due to chromatin dispersion during cell activation and/or cell proliferation and do not constitute reliable evidence of malignancy. In contrast, discrete aneuploid DNA peaks are confined to malignant lesions, but are seen almost exclusively in the advanced stages in which the diagnosis can be established easily based on routine histological criteria. These data indicate that DNA measurements by flow cytometry is of only limited help in the early recognition of CTCL and support the view that the lymphoid infiltrate in early CTCL may be reactive (rather than neoplastic) or alternatively may contain only minor reactive (rather than neoplastic) or alternatively may contain only minor populations of abnormal (malignant) cells which cannot be detected by currently available DNA measurement techniques.

DNA-cytophotometry of lymph node touch imprints in cutaneous T-cell lymphoma

Scanning DNA-cytophotometry was performed on touch imprints of 26 lymph nodes (LN) obtained from 25 patients with cutaneous T-cell lymphoma (CTCL), stained by the Feulgen technique, and interpreted without knowledge of histopathologic diagnosis. Four patterns of DNA distribution were identified, but only histograms that demonstrated cells containing nuclei with more than 4C DNA content (hypertetraploidy) reliably distinguished LN involved with CTCL from LN with reactive changes; for example, dermatopathic lymphadenitis. An abnormal DNA histogram with evidence of hypertetraploidy was demonstrated in 9 of 12 LN showing histopathologic evidence of involvement compared with no abnormal histograms in 14 LN without histopathologic involvement. One LN that was diffusely involved with CTCL had a DNA distribution characteristic of a relatively high level of cell proliferation, but without definite hypertetraploidy. Cytogenetic studies on the blood of this patient, who had Sézary syndrome, demonstrated a clone of lymphocytes with a pseudodiploid karyotype without a related polyploid subline. The remaining two histopathologically involved LN had normal DNA histograms; these LN were only focally involved with CTCL. These observations indicate that DNA-cytophotometry correlates well with the histopathologic findings in LN diffusely involved with CTCL, but may be normal in LN with focal involvement or in those that contain cytogenetically abnormal cells with a near-diploid DNA content.

Screening tests for Sezary cells in cutaneous T-cell lymphomas

Blood samples from normal individuals (n = 7), from patients with cutaneous T-cell lymphomas (Sezary syndrome = 7; mycosis fungoides = 18) and from patients with chronic benign skin disease (n = 8) were examined for the presence of Sezary cells. The samples were analysed using a Coulter model S Plus IV with a three Cell Population upgrade, and a Becton Dickinson FACS analyser; and the results were compared with those obtained from morphological examination of peripheral blood films. Using the FACS analyser a population of aneuploid cells was only identified in two out of eight patients with confirmed circulating Sezary cells. This was in contrast to the results from the Coulter S Plus IV which detected an abnormality in six out of the eight samples with confirmed circulating Sezary cells. These results indicate that leukocyte volume analysis is a useful, additional screening tool for the identification of Sezary cells.

Activated and cycling lymphocytes in benign dermal lymphocytic infiltrates including psoriatic skin lesions

Single-cell DNA measurements obtained using flow cytometry have previously been used as a diagnostic tool for various malignant diseases. We used this technique to characterize the dermal infiltrates of 14 patients with psoriatic skin lesions and 22 patients with various benign skin disorders. The DNA histograms of all of the patients exhibited an increased number of cells showing propidium-iodide fluorescence in the hyperdiploid region as compared to those seen in control DNA histograms of normal blood mononuclear cells. The calculated DNA indices revealed one hyperdiploid (G0/G1) peak in 17 cases and two hyperdiploid (G0/G1) peaks in 13 cases. The results suggest that the dermal lymphocytic infiltrate consists of (1) lymphocytes in the cell-division cycle, (2) non-cycling lymphocytes (G0) and (3) activated lymphocytes that may either remain in a non-cycling state or enter the cell cycle.

Single cell DNA measurements in benign cutaneous lymphoid infiltrates and in positive patch tests

Cellular DNA in skin biopsies from eighteen patients with positive patch tests and eleven patients with benign lymphocytic skin infiltates (cutaneous lymphocytoma, lymphoplasia or Jessner's lymphotic infiltrate) was estimated by flow cytometry of propidium iodide-stained dermal cells. Specimens from three patients with patch tests and one with cutaneous lymphocytoma had DNA histograms similar to those of normal blood mononuclear cells. The remaining patients demonstrated DNA histogram abnormalities in the form of hyperdiploid peaks in forty-two of forty-five specimens. The estimated proportion of cells in the S-phase was similar in patch tests (median: 9.2%) and in benign lymphocytic skin infiltrates (median: 9.6%). The median number of cells in the G2/M-phase was 3.1% in both groups of disorders. These data indicate DNA content heterogeneity of the dermal cells in benign lymphocytic skin infiltrates. This may be attributed to DNA replication and/or chromatin dispersion during cellular activation and proliferation. The data also emphasize that hyperdiploid peaks are not necessarily indicative of the presence of separate cell clones.

Early diagnosis of cutaneous T-cell lymphoma by DNA flow cytometry on skin biopsies

Seven patients with mycosis fungoides early plaque stage with nondiagnostic histology had single-cell DNA content measured by flow cytometry for estimation of clonal ploidy. A total of 63 skin specimens were examined by histology and DNA measurements concurrently during the course of the disease. In addition, six patients had blood samples studied. All seven patients demonstrated aneuploid DNA histograms when the specimens were obtained from skin lesions. In 36 specimens the aneuploid peaks were hyperdiploid. By sequential studies one patient demonstrated two different aneuploid cell clones, one located in the hyperdiploid region and one located in the hypotetraploid region. All patients developed mycosis fungoides which were histologically confirmed, and the time from first aneuploid DNA histogram until diagnostic histology varied from 5 to 21 months (median, 12 months). In six of the patients a normal diploid DNA histogram was found of peripheral blood lymphocytes. The finding of aneuploidy in patients with early mycosis fungoides who still have a nondiagnostic histology emphasizes the value of flow cytometry as a complementary diagnostic aid which facilitates an early diagnosis.

Controversies in mycosis fungoides

Most clinicians agree that mycosis fungoides is the prototypic cutaneous T cell lymphoma. However, certain clinical characteristics indicate that this disorder may begin as a reactive rather than a neoplastic process. The concept of a nonneoplastic etiopathogenesis of mycosis fungoides is further supported by recent data on the function of Langerhans cells, a population of epidermal cells known to play a critical role in immune surveillance and the development of contact sensitivity. It has been suggested that chronic occupational exposure to environmental allergens results in persistent antigenic stimulation, leading to a breakdown in immune surveillance and eventually, malignancy. Modern laboratory technics have enhanced the clinician's ability to diagnose and stage mycosis fungoides. Data obtained from such studies have indicated that systemic spread may occur much earlier in the course of disease than has previously been appreciated. The therapeutic implications of such knowledge are as yet uncertain.