Immunohistochemical differentiation of follicular lymphoma from florid reactive follicular hyperplasia with monoclonal antibodies reactive on paraffin sections

Lymphoma immunophenotyping: a new era in paraffin-section immunohistochemistry

Recent advances in immunohistochemistry have made it possible to investigate lymphomas for the expression of a wide range of antigens in fixed tissues. Epitope retrieval, sensitive detection methods, and the availability of new monoclonal antibodies have all contributed to one's ability to perform detailed immunophenotyping that previously could only be done in cryostat sections or by flow cytometry. Current lymphoma classifications make use of characteristic immunophenotypic profiles that aid in the reproducible diagnosis and subcassification of these neoplasms. The following is a review of the current state of immunophenotyping for lymphoid neoplasms in fixed tissues.

Epstein-Barr virus expression in Hodgkin's disease: Correlation with histologic subtypes and T and B lymphocyte distribution

BACKGROUND

The pathogenesis of Hodgkinâs disease (HD) has been linked to Epstein-Barr virus (EBV). Some histologic subtypes show a high level of viral expression. These include mixed cellularity (MCHD) and nodular sclerosis (NSHD) subtypes. Grade II NSHD is a more aggressive variant of HD. Lymphocyte predominant (LPHD) is a B cell lymphoproliferative disorder that has not been associated with EBV expression. Infiltrating lymphocytes in HD are predominantly T lymphocytes, with a minor component of B lymphocytes. In the current study, EBV expression was tested in cases of HD in relation to histologic subtypes. An attempt was made at correlating EBV expression with T and B lymphocyte distribution in lymph nodes involved by HD.

METHOD

Formalin-fixed paraffin-embedded tissue from 62 cases of HD were tested for EBV mRNA expression, using the EBER-1 probe and in situ hybridization. T and B lymphocyte distribution and their ratios were evaluated using antibodies to T and B lymphocytes (UCHL-1 [CD45 RO] and CD 20, respectively), and the immunoperoxidase technique.

RESULTS

The cases were seen in 38 male and 24 female patients, with an age range of 3 to 72 years (median 25 years). There were 30 cases of grade I and 15 cases of grade II NSHD, 9 cases of MCHD and 8 cases of LPHD. EBV mRNA expression was seen in 29 cases (46%). This expression was seen in 8 cases of grade I NSHD (26%), 13 cases of grade II NSHD (86%) and 8 cases of MCHD (88%). None of the cases of LPHD showed viral expression. T to B lymphocyte ratios in EBV-positive cases ranged from 1/6 to 8/1, and ranged from 2/1 to 20/1 in EBV-negative cases (P=0.06). Nine of the 29 positive cases (31%) showed equal T/B lymphocyte ratios (n=4), or predominance of B lymphocytes (n=5). None of the EBV-negative cases showed predominance of B lymphocytes.

CONCLUSION

Our study confirms previously reported findings of the prevalence of EBV expression in MCHD and NSHD. Our findings also suggest that EBV expression may be more commonly seen in aggressive forms of HD. Decreased numbers of T lymphocytes in these aggressive subtypes may suggest that a process of more profound T lymphocyte depletion is occurring in these cases, leading to uncontrolled EBV replication and more aggressive disease.

Ormond's disease: Aspetti anatomo-patologici: Ormond's disease: Histopathological features

Histopathological studies have significantly contributed to clarifing the pathogenetic mechanisms of idiopathic retroperitoneal fibrosis (Ormond's disease), confirming in most cases its inflammatory nature. In this review we describe the principal pathologic features of the lesion, describing the different inflammatory and fibrogenic cell components. In addition, the differential diagnosis of Ormond's disease and the clinical role of histopathology and immunophenotypical analysis are briefly discussed.

B- and T-Lymphocyte distribution in benign and malignant lymphoepithelial lesions of the parotid gland: Correlation with Epstein-Barr virus expression and a proposed mechanism of malignant transformation

Epstein-Barr virus expression in malignant lymphoepithelial lesions (LEL) of the parotid gland has been well established. The virus is occasionally expressed in benign LEL, especially in immunocompromised hosts. The pathogenesis of the disease as it relates to virus expression and lymphocyte subsets has not been clearly defined. In this study, we attempted to identify B- and T-lymphocyte distribution in the lesions as it relates to EBV expression in LELs of the parotid gland. Formalin-fixed paraffin-embedded sections of 18 cases of LEL of the parotid gland were immunohistochemically tested for the distribution of B- and T-lymphocytes in the lesions, using the antibodies L-26 (CD 20) for B-lymphocytes and UCHL-1 (CD-45RO) for T-lymphocytes. The sections were also tested by in situ hybridization for EBV mRNA expression, using the EBER-1 probe specific for EBV-1 gene. The 18 lesions included seven malignant LEL, seven benign LEL and four benign lymphoepithelial cysts. All malignant LELs showed a high and diffuse level of epithelial expression of EBV mRNA. Of the 11 benign lesions, only one case showed focal epithelial expression of EBV mRNA. This was a case of benign LEL in an HIV-positive male. All the benign lesions, except that expressing EBV mRNA, showed a T-/B-lymphocyte ratio averaging 2:1. All cases expressing EBV mRNA, including the case of benign LEL in the HIV-positive patient, showed a T-/B-lymphocyte ratio averaging 1:3. Our findings suggest that a T-lymphocyte-mediated immune response may play an essential role in suppressing proliferation of EBV in benign LEL of the parotid gland. This immune mechanism may be significantly disturbed in the malignant lesions, leading to uncontrolled viral replication and carcinogenesis.

A comparative study of the value of immunohistochemistry and the polymerase chain reaction in the diagnosis of follicular lymphoma

We have compared the value of immunohistochemical and polymerase chain reaction (PCR) techniques in distinguishing follicular lymphoma from follicular hyperplasia in formalin-fixed paraffin-embedded tissues of 41 follicular lymphomas, 15 reactive lymph nodes and 5 reactive tonsils. Immunohistochemistry demonstrated bcl-2 protein in the follicle centre cells of 97% of follicular lymphomas whereas monoclonal immunoglobulin light chain was detected in 83% of cases. Assessing the lowest proliferating follicle of each case by MIB-1 immunostaining, proliferation fractions in the lymphomas varied from 0.5% to 59% (mean 15.6%). Over 80% of lymphomas had proliferation fractions of less than 25%. PCR detected gene rearrangement either at the bcl-2 locus, or at the IgH locus, or at both loci in 32%, 44% and 61% of lymphomas, respectively. The follicle centre cells of the reactive lymph nodes and tonsils were all bcl-2 protein negative and polytypic for kappa and lambda light chains. Proliferation fractions of the lowest proliferating follicle in each reactive case ranged from 30.5% to 86.8% (mean 64.9%). Rearrangements of the bcl-2 or IgH loci were not detected in any reactive case. This study demonstrates that bcl-2 and light chain immunostaining are the most consistently helpful aids to diagnosing follicular lymphoma. A low proliferation fraction also indicates lymphoma but a high proliferation fraction does not exclude the diagnosis. Immunostaining with a combination of anti bcl-2 and MIB 1 antibodies is a sensitive and specific method for identifying follicular lymphoma, is technically simple to perform and easy to interpret. In occasional cases, where immunostaining gives equivocal results, PCR analysis can confirm lymphoma, but a negative result does not exclude the diagnosis.

Distinction of follicular hyperplasia from follicular lymphoma in B5-fixed tissues: comparison of MT2 and bcl-2 antibodies

The distinction between follicular hyperplasia (FH) and follicular lymphoma (FL) is one of the classic problems in diagnostic hematopathology. Both MT2 and bcl-2 antibodies have been reported to be useful in making this distinction. To compare the utility of these two commercially obtained antibodies in paraffin-embedded sections, B5-fixed sections from 21 cases of follicular hyperplasia and from 46 follicular lymphomas were immunostained and the follicles evaluated. Neither MT2 nor the bcl-2 antibody showed definite follicular positivity in FH. In contrast, 66% of FLs were MT2 positive and 89% were bcl-2 positive (P < .02). MT2 staining was equivocal in 30% of FHs and 7% of FLs, whereas bcl-2 staining was equivocal in only one FL. In addition, MT2 staining was unsatisfactory in three cases. CD10 was negative (0% to 3%) in the three bcl-2-negative FLs tested and positive (> 10%) in 26 of 38 bcl-2-positive cases. These results demonstrate the utility of the commercially obtained bcl-2 antibody in distinguishing FL from FH in B5-fixed, paraffin-embedded tissue sections. They also illustrate the superiority of the bcl-2 antibody over MT2, which was less sensitive and more problematic to interpret.