Mucosa-associated lymphoid tissue (MALT) lymphoma mainly consists of three types of tumor B cells, small (centrocyte-like), scattered large transformed, and intraepithelial. However, it is difficult to differentiate tumor B cells from reactive B cells at the cellular level. We examined five cases of API2-MALT1 fusion-positive MALT lymphoma of the lung. A single paraffin section for each case was subjected to sequential retrieval of whole-slide imaging (WSI) data of hematoxylin and eosin (HE) staining, immunofluorescence staining for CD79a, and fluorescence in situ hybridization (FISH) for the MALT1 split. We counted the number of MALT1 split-positive or MALT1 split-negative cells among CD79a-positive cells. The MALT1 split was detected in 59, 46, and 76 % of small, large, and intraepithelial B cells, respectively. A review of the HE-WSI data showed that cytomorphological distinction between the MALT1 split-positive and MALT1 split-negative B cells was virtually impossible. None of CD79a-negative lymphoid cells, epithelial cells, and microvascular endothelial cells was positive for MALT1 splits. As API2-MALT1 fusion is an early and critical event in the lymphomatogenesis, our findings are best interpreted as that a considerable number of B cells, either small, large, or intraepithelial, are reactive cells and that it is difficult to distinguish cytomorphologically between tumor B cells and reactive B cells. These findings suggest that the tumor architecture may be the central factor for making a correct histopathological diagnosis of MALT lymphoma. The sequential WSI of HE staining, immunofluorescence staining, and FISH as described here is a useful tool for pathological analysis at the cellular level.
Detection of HTLV-1 provirus using paraffin tumor sections may assist the diagnosis of adult T-cell leukemia/lymphoma (ATLL). For the detection, non-quantitative PCR assay has been reported, but its usefulness and limitations remain unclear. To our knowledge, quantitative PCR assay using paraffin tumor sections has not been reported. Using paraffin sections from ATLLs and non-ATLL T-cell lymphomas, we first performed non-quantitative PCR for HTLV-1 provirus. Next, we determined tumor ratios and carried out quantitative PCR to obtain provirus copy numbers. The results were analyzed with a simple regression model and a novel criterion, cut-off using 95 % rejection limits. Our quantitative PCR assay showed an excellent association between tumor ratios and the copy numbers (r = 0.89, P < 0.0001). The 95 % rejection limits provided a statistical basis for the range for the determination of HTLV-1 involvement. Its application suggested that results of non-quantitative PCR assay should be interpreted very carefully and that our quantitative PCR assay is useful to estimate the status of HTLV-1 involvement in the tumor cases.In conclusion, our quantitative PCR assay using paraffin tumor sections may be useful for the screening of ATLL cases, especially in HTLV-1 non-endemic areas where easy access to serological testing for HTLV-1 infection is limited.Key words: adult T-cell leukemia/lymphoma, HTLV-1 provirus, paraffin tumor sections, quantitative PCR Adult T-cell leukemia/lymphoma (ATLL), a human T-cell malignancy derived from CD4+ T-cells, is induced by human T-lymphotropic virus type 1 (HTLV-1), and the HTLV-1 provirus is clonally integrated into the tumor cells.1-3 The diagnosis of ATLL can be established on the basis of clinical and laboratory features in addition to morphological and immuno-pathological evaluation of the tumor cells. 4 Accurate diagnosis of ATLL is very important since the prognosis for ATLL patients is much worse than for those with other types of peripheral T-cell tumors.5 Serology for HTLV-1 infection is usually mandatory, and Southern blotting is used for detection of the monoclonal integration of the HTLV-1 provirus genome. 5 However, it is not uncommon for paraffin tumor sections to be the only materials available for pathological diagnosis. Easy access to HTLV-1 serological testing may sometimes be difficult, especially in HTLV-1 non-endemic areas where ATLL is very rare, leading to a misdiagnosis or a delay in the final diagnosis. Non-quantitative PCR methods to detect HTLV-1 provirus DNA have been applied to paraffin tumor sections and have assisted the diagnosis of ATLL.6-8 However, their usefulness and limitations have not been well clarified. To the best of our knowledge, quantitative PCR analysis for the HTLV-1 provirus using paraffin tumor sections has not been carried out. In this study, we quantified HTLV-1 provirus copy numbers using paraffin ATLL sections, and the data was analyzed by a simple regression model and a novel criterion, cut-off using 95 % rejection limits. 9MATERIALS ...
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