Heterogeneity of bcl-2 expression in MALT lymphoma

Die-hard survivors: heterogeneity in apoptotic thresholds may underlie chemoresistance

The unmatched efficacy of microtubule-targeting agents (MTAs) as chemotherapeutics was once assumed to originate from their impact on mitotic processes; however, this misconception is being eroded by amassing data that MTAs instead target interphase functions in patients' tumors. What remains murky is how MTAs target malignant cells over non-malignant ones if proliferation rates do not distinguish them. In many instances, malignant cells are actually more 'primed' for apoptosis than non-malignant ones. Nevertheless, even if most cells within the tumor are more apoptosis-susceptible than those in healthy tissues, there likely exist small subpopulations of apoptosis-resistant clones that engender incomplete responses to MTAs and relapse. Therefore, intratumor heterogeneity in terms of proximity to the apoptotic threshold must be better understood to facilitate the design of chemotherapeutic regimens, which may benefit from including drugs like BH3 mimetics that help in lowering the apoptotic threshold of tumor cells within these chemoresistant subpopulations.

A solitary rectal mucosa-associated lymphoid tissue (MALT) lymphoma

Mucosa-associated lymphoid tissue (MALT) is a type of extra nodal malignant lymphoma seen in organs such as the stomach, thyroid and salivary glands. Furthermore, occurrence of colorectal MALT lymphoma is extremely rare. We report a case of a solitary rectal MALT lymphoma treated by surgical resection and radiotherapy. Lymphoma should be considered as a rare differential diagnosis when dealing with large bowel pathology. We would advocate the use of surgery as a primary treatment option for a medically fit patient.

Small Lymphoid Proliferations in Extranodal Locations

Context.—Low-grade non-Hodgkin lymphomas frequently involve extranodal sites including the gastrointestinal tract, skin, and lung, either selectively or as part of widespread dissemination. Differentiation from inflammatory or infectious conditions requires knowledge of specific histologic characteristics of the various entities as well as ancillary techniques.

Objective.—To describe the key features and provide diagnostic clues to the identification of specific extranodal low-grade lymphomas of T-cell and B-cell types including small lymphocytic lymphoma, follicular lymphoma, mantle cell lymphoma, extranodal marginal zone B-cell lymphomas of mucosal-associated lymphoid tissue, and hairy cell leukemia. Histologic and cytologic features are highlighted, as well as appropriate integration of results of ancillary diagnostic studies including flow cytometry, immunohistochemistry, molecular features, and cytogenetics.

Data Sources.—The published literature as well as personal experience from a specialized hematopathology practice at a large university medical center.

Conclusions.—Correct identification of extranodal low-grade lymphomas and differentiation from hyperplastic and inflammatory or infectious processes require the ability to distinguish each of the specific entities discussed. Ancillary studies are often indispensable in reaching a correct diagnosis.

Low-grade mucosa-associated lymphoid tissue lymphoma involving the kidney: report of 3 cases and review of the literature

Low-grade B-cell lymphoma of mucosa-associated lymphoid tissue involving the kidney is rare. We report a series of 3 cases. The first case occurred in an 83-year-old woman who presented with back pain. The second case was a 53-year-old man with a history of sarcoidosis who was found, in the course of evaluation of sarcoidosis, to have a right renal mass. The third case occurred in a 72-year-old man who had a history of periorbital mucosa-associated lymphoid tissue lymphoma and had been treated with surgery and radiation 1 year prior to this presentation. Histologically, all 3 patients showed infiltrate of uniform small-to-medium-sized lymphocytes with irregular nuclear contours and abundant cytoplasm resembling centrocytes or monocytoid lymphoid cells. The first patient received chemotherapy without complications. The second patient underwent a partial nephrectomy and was asymptomatic at the subsequent follow-up. The third patient developed a pulmonary embolism following nephrectomy, and further follow-up is not available.

Maltoma of the thyroid and Sjögren's syndrome in a woman with Hashimoto's thyroiditis

We report the case of a 70-yr-old woman with maltoma of the thyroid, Sjögren's syndrome, and a history of Hashimoto's thyroiditis. The patient underwent a total thyroidectomy for a recently growing mass of the thyroid, while being treated with L-thyroxine for Hashimoto's thyroiditis. Postoperatively, routine histologic examination was consistent with the diagnosis of chronic lymphocytic thyroiditis of autoimmune etiology. Three years later, the patient presented with high temperature, anorexia, and coughing. This time, a microscopic examination of deeper thyroid tissue sections and an immunohistochemical study revealed a low-grade, non-Hodgkin lymphoma, MALT type. Simultaneously, the diagnosis of Sjögren's syndrome was established and the patient is currently under investigation for generalized lymphoma. This case clearly demonstrates the difficulty in differentially diagnosing Hashimoto's thyroiditis from low-grade MALT lymphoma by the use of routine histologic examination.

18q21 Rearrangement and trisomy 3 in extranodal B-cell lymphomas: a study using a fluorescent in situ hybridisation technique

t(11;18)(q21;q21) Translocation and trisomy 3 are the most common chromosomal aberrations reported in low-grade mucosa-associated lymphoid tissue (MALT) lymphoma. The current study aims to investigate the frequency of these chromosomal aberrations in a series of 52 extranodal B-cell lymphomas. The tumours were categorised into three histological grades: grade 1 (low-grade lymphoma of MALT type), grade 2 [diffuse large B-cell lymphoma (DLBCL) with MALT component] and grade 3 (DLBCL without MALT component). Fluorescence in situ hybridisation analyses on paraffin tissue sections were performed using a locus-specific probe for the 18q21 region and a centromeric probe for chromosome 3. The 18q21 rearrangement was detected in 9 of 40 (23%) cases, including 7 of 23 (30%) grade-1 and 2 of 11 (18%) grade-3 tumours. Amplification of the 18q21 region was detected in 10 of 40 (25%) cases, and trisomy 3 was detected in 9 of 34 (26%) cases. Amplification of the 18q21 region may be an important alternative pathogenetic pathway in MALT lymphoma and was found almost exclusively in tumours without 18q21 rearrangement. Our study showed that tumours with 18q21 rearrangement and 18q21 amplification develop along two distinct pathways, and the latter was more likely to transform into high-grade tumours upon acquisition of additional genetic alterations, such as trisomy 3. Trisomy 3 was more frequently found in coexistence with 18q21 abnormalities, suggesting that it was more likely to be a secondary aberration.

Immunogenetic analysis of gastric MALT lymphoma-like lesions induced by Helicobacter pylori infection in neonatally thymectomized mice

Most gastric mucosa-associated lymphoid tissue (MALT) lymphomas are caused by Helicobacter pylori (H. pylori) infection. We previously reported that acquired lymphoid follicles with germinal centers were induced by H. pylori infection in neonatally thymectomized (nTx) mice. In the present study, we developed gastric MALT lymphoma-like lesions in nTx mice by long-term H. pylori infection, and performed immunogenetic analyses. BALB/c mice were thymectomized on the 3rd day after birth. At 6 weeks of age, mice were orally infected with 10(8) H. pylori and serially killed 2, 4, 6, and 12 months later. Normal BALB/c and noninfected nTx mice served as controls. Follicle formation occurred after 2 months of H. pylori infection in the nTx mice. Follicle formation and infiltration of intraepithelial lymphocytes progressed in a time-dependent manner. Lymphoepithelial lesions, a characteristic feature of MALT lymphoma, also occurred in a time-dependent manner (100% at 12 months). Serum immunoelectrophoresis revealed a monoclonal band (M-protein) in 30% (3/10) of mice 6 months after infection. M-protein-positive mice had amplification of one or two IgM and/or IgG heavy-chain genes in the gastric B lymphocytes, as determined with polymerase chain reaction, suggesting mono- or oligoclonality. Overexpression of Bcl-X(L) protein was immunohistologically observed in the infiltrating B lymphocytes and in some follicular B lymphocytes in 80% (8/10) of the cases at 12 months. Thus, H. pylori infection is involved in the development of gastric MALT lymphoma-like lesions in nTx mice. Our mouse model is useful for clarifying the pathogenetic mechanism of gastric MALT lymphoma by H. pylori infection.

Clinicopathologic and immunohistochemical study of surgically treated primary gastric MALT lymphoma

BACKGROUND AND OBJECTIVES

B-cell MALT lymphoma is a well-recognized entity and its characterization as low-grade (LG) and high-grade (HG) lymphoma has been widely accepted. In the present study we reviewed a series of 95 surgical specimens of primary gastric MALT lymphoma selected between 1979 and 1998. Immunohistochemical expression of p53, bcl-2, and Ki67 and Helicobacter pylori (Hp) infection was evaluated, along with a correlation with clinical outcome.

METHODS

A morphologic and immunohistochemical analysis, including p53, bcl-2, and Ki67 expression, was carried out in all cases. A complete follow-up was obtained in 49 patients and in these cases a survival analysis was performed.

RESULTS

bcl-2 protein was highly expressed in 25 of 25 assessed LG tumors and in 20 of 24 assessed HG tumors. p53 protein was expressed in 13 of 25 assessed LG tumors and in 21 of 24 assessed HG tumors. High proliferation rate as expressed by Ki67 was detected in 15 of 25 assessed LG tumors and in 23 of 24 assessed HG tumors. Hp infection was detected in 11 of 16 assessed LG tumors and 2 of 10 assessed HG tumors. Median survival rates were 72 months for LG tumors and 24 months for HG tumors.

CONCLUSIONS

A significant inverse relationship between Hp infection and histological grade was found. High p53 expression and high-proliferation rate correlated with HG tumors. However, a correlation between p53, bcl-2, and Ki67 expression with clinical outcome was not found.

Focal follicular features in tonsillar diffuse large B-cell lymphomas: follicular lymphoma with diffuse areas or follicular colonization

Focal follicular features in diffuse large B-cell lymphomas (DLBCLs) are bound to raise the question of follicular lymphoma (FL) with diffuse areas, because the diagnosis of FL is based on the presence of follicular areas, even though focal. We report 7 cases of primary tonsillar DLBCLs with focal follicular features that presented with morphologic, immunohistochemical, and biological features distinct from those of FL. Histologically, these tumors were characterized by involvement of pericryptal follicles with adjacent dominant diffuse areas. Monomorphous large tumor cells were evenly spaced with abundant, often clear cytoplasm, and blastoid nuclei often with a delicate nuclear membrane. Importantly, residual germinal centers (GCs) were present in the form of either an intrafollicular GC remnant or an isolated GC in the midst of diffuse tumor. An extrafollicular and/or parafollicular growth pattern was also observed. Bcl-6 staining revealed a predominantly sporadic occurrence of Bcl-6(+) cells, comprising <50% of tumor cells, and none displayed diffusely dense collections (>75%) of Bcl-6(+) tumor cells characteristic of the GC or FL. Staining for CD10 was negative in 6 cases. Five of 7 patients were younger than 60, the median age of other patients with primary tonsillar DLBCL. No extratonsillar involvement was seen at 18 months after diagnosis. After chemotherapy or radiotherapy, complete remission was achieved with ease in all patients, but 2 patients who were treated with chemotherapy alone relapsed at 24 and 30 months. In conclusion, tonsillar DLBCL includes a small (10%) but distinct subgroup that warrants distinction from FL with predominant diffuse areas or de novo DLBCL. It appears that the focal follicular features in tonsillar DLBCL likely represent follicular colonization of marginal zone B-cell lymphoma, probably high-grade, if the possibility of FL is excluded.

Proteins encoded by genes involved in chromosomal alterations in lymphoma and leukemia: clinical value of their detection by immunocytochemistry

Acquired chromosomal anomalies (most commonly translocations) in lymphoma and leukemia usually result in either activation of a quiescent gene (by means of immunoglobulin or T-cell-receptor promotors) and expression of an intact protein product, or creation of a fusion gene encoding a chimeric protein. This review summarizes current immunocytochemical studies of these 2 categories of oncogenic protein, with emphasis on the clinical relevance of their detection in diagnostic samples. Among the quiescent genes activated by rearrangement, expression of cyclin D1 (due to rearrangement of the CCND1 [BCL-1] gene) is a near-specific marker of t(11;14) in mantle cell lymphoma; BCL-2 expression distinguishes follicular lymphoma cells from their nonneoplastic counterparts in reactive germinal centers and appears to be an independent prognostic marker in diffuse large cell lymphoma; and TAL-1 (SCL) expression identifies T-cell acute lymphoblastic neoplasms in which this gene is activated. The protein products of other genes activated by chromosomal rearrangement have a role as markers of either lineage (eg, PAX-5 [B-cell-specific activator protein] for B cells, including B-lymphoblastic neoplasms), or maturation stage (eg, BCL-6 for germinal-center and activated B cells and MUM-1/IRF4 for plasma cells). Currently, no hybrid protein encoded by fusion genes is reliably detectable by antibodies recognizing unique junctional epitopes (ie, epitopes absent from the wild-type constituent proteins). Nevertheless, staining for promyelocytic leukemia (PML) protein will detect acute PML with t(15;17) because the microspeckled nuclear labeling pattern for PML-RARalpha is highly distinctive. Similarly, antibodies to the anaplastic lymphoma kinase (ALK) tyrosine kinase are valuable (because wild-type ALK is not found in normal lymphoid tissue) in detecting neoplasms (CD30-positive large T-cell lymphomas) with t(2;5) or its variants. Thus, immunocytochemical detection of the products of many rearranged genes in lymphoma and leukemia can be clinically informative and provide information on cellular and subcellular protein expression that cannot be inferred from studies based on messenger RNA.

Primary marginal zone lymphoma of the thymus

Primary low-grade B-cell lymphomas of the thymus are rare, with only 7 reported cases in the literature. We describe 3 cases of primary low-grade thymic lymphoma. All had histologic features of extranodal marginal zone lymphoma and were composed predominantly of small lymphocytes with variable components of monocytoid cells and plasma cells. Overt transformation to large cell lymphoma occurred in 1 case. The neoplastic cells were immunoreactive for the B-cell marker CD20 and were positive for bcl-2 in 2 cases. Two of 3 patients had a long-standing history of autoimmune disease. Based on these findings and those of previously reported cases, marginal zone lymphoma is the predominant type of low-grade thymic B-cell lymphoma. These tumors seem to be more common in patients with autoimmune disorders, and as observed with marginal zone lymphoma arising at other anatomic sites, they may undergo transformation to a higher grade lymphoma.

Mucosa-associated lymphoid tissue (MALT) lymphoma of the rectum with chromosomal translocation of the t(11;18)(q21;q21) and an additional aberration of trisomy 3

A rare case of primary mucosa-associated lymphoid tissue lymphoma (MALT) of the rectum is reported. A 56-yr-old man was referred to our hospital for further examination and treatment of rectal neoplasm. A physical examination and laboratory data showed no special abnormalities. However, endoscopic colorectal observation revealed multiple red and slightly elevated nodular lesions with erosive changes of the rectum. The lesions were composed of diffuse, small atypical lymphoid cells (i.e., centrocyte-like cells) and were stained with L26 and BCL-2 but not cyclin D1. Surface markers of cells obtained from biopsy specimens were CD5-, CD10-, CD19+, CD20+, kappa+, and lambda-. No BCL-2 gene rearrangement was observed. The clonal karyotype of t(11;18)(q21;q21) was observed in six of nine lymphoid cells. Trisomy was also identified two of 144 cells by fluorescence in situ hybridization. We report a rare case of the rectal MALT lymphoma bearing characteristic chromosomal aberrations; t(11;18)(q21;q21) and trisomy 3. We suggest that chromosomal analysis using biopsy specimens may be useful for the diagnosis of MALT lymphoma.

Apoptosis and the Bcl-2 gene family -- patterns of expression and prognostic value in stage I and II follicular center lymphoma

PURPOSE

The prognostic significance of spontaneous levels of apoptosis and Bcl-2, Bax, and Bcl-x protein expression in follicular center lymphoma (FCL) is unknown. The objectives of this retrospective study were (1) to investigate the relationship between pretreatment apoptosis levels and long-term treatment outcome in patients with Stage I and II FCL; (2) to define the incidence and patterns of Bax and Bcl-x protein expression in human FC; and (3) to determine the relationship of Bcl-2, Bax, and Bcl-x expression with spontaneous apoptosis levels and clinical outcome in localized FCL.

METHODS AND MATERIALS

Between 1974 and 1988, 144 patients with Stage I or II FCL were treated. Hematoxylin and eosin (H & E) stained tissue sections of pretreatment specimens were retrieved for 96 patients. Treatment consisted of regional radiation therapy (XRT) for 25 patients, combined modality therapy (CMT) consisting of combination chemotherapy and XRT for 57 patients, and other treatments for 14 patients. Median follow-up for living patients was nearly 12 years. The apoptotic index (AI) was calculated by dividing the number of apoptotic cells by the total number of cells counted and multiplying by 100. Expression of Bcl-2, Bax, and Bcl-x proteins was assessed using immunohistochemistry.

RESULTS

The mean and median AI values for the entire group were 0.53 and 0.4, respectively (range: 0-5.2). The AI strongly correlated with cytologic grade, with mean AI values of 0.25 for grade 1, 0.56 for grade 2, and 0.84 for grade 3 (p < 0.0005; Kendall correlation). A positive correlation was present between grouped AI and grouped mitotic index (MI) (p = 0.014). For patients treated with CMT, an AI < 0.4 correlated with improved freedom from relapse (FFR) p = 0.0145) and overall survival (OS) (p = 0.0081). An AI < 0.4 did not correlate with clinical outcome for the entire cohort or for patients receiving XRT only. Staining of tumor follicles for the Bcl-2 protein was positive, variable, and negative in 73%, 15%, and 12% of cases, respectively. Positive staining of tumor follicles was observed in 96% of cases for both the Bax and Bcl-x proteins. Expression of Bcl-2, Bax, or Bcl-x did not correlate with AI or clinical outcome.

CONCLUSION

The level of spontaneous apoptosis in pretreatment specimens correlates with cytologic grade of FCL and is a significant predictor of FFR and OS for patients with localized FCL receiving CMT.

HIV-associated lymphoepithelial cysts and lesions: morphological and immunohistochemical study of the lymphoid cells

AIMS

To determine the morphology, immunophenotype and bcl-2 protein status of intraepithelial lymphocytes in HIV-positive lymphoepithelial lesions.

METHODS AND RESULTS

Seventeen cases (from adults and children) of HIV-associated parotid and lung lymphoid lesions were examined. In addition, three lymphoepithelial cysts from HIV-negative patients were studied in parallel. Immunohistochemistry was performed on paraffin embedded tissue with the following antibodies: CD20, CD79a, CD3, CD4, CD8, bcl-2, CAM5.2, AE1/3, MIB1, kappa/lambda light chains and EBV-LMP-1. Heavy chain rearrangement was sought by polymerase chain reaction (PCR) in four of the cases. The lymphocytes participating in lymphoepithelial lesions of HIV-positive patients had the morphology of centrocyte-like cells with occasional cells resembling centroblasts. The majority of these cells were of B-cell lineage, but occasional intraepithelial T-cells (CD8 positive, CD4 negative) were also present. T-cells also formed a significant component of the infiltrative lymphoid cells outside the lymphoepithelial lesions. These were mainly CD8 positive, but very occasional CD4-positive T-cells were also noted. None of the cases showed light chain restriction and the four cases did not demonstrate heavy chain rearrangement by molecular biology. The interesting finding was the absence of bcl-2 expression by the intraepithelial lymphocytes. In contrast, the intraepithelial lymphocytes seen in the non-HIV setting were strongly bcl-2 positive. The majority of these were B-cells, and very occasional CD8 and CD4 positive T-cells formed the intraepithelial population.

CONCLUSION

It is postulated that this finding is due to the HIV causing down-regulation of bcl-2 protein.

Detection of the apoptosis-suppressing oncoprotein bcl-2 in salivary gland lymphoma

The bcl-2 proto-oncogene encodes an inner mitochondrial membrane protein that blocks apoptosis and programmed cell death in human lymphoid tissue. In this study a monospecific anti-human bcl-2 antibody that is reactive in formalin-fixed tissues was used with an avidin-biotin complex immunoperoxidase method to evaluate 41 cases of lymphoproliferative disorders of the salivary gland. The study cases were 26 primary salivary gland lymphomas (including 21 B-cell lymphomas four T-cell lymphomas and one true histiocytic lymphoma) and 15 cases of myoepithelial sialadenitis. Bcl-2 expression is restricted to the mantle zone and interfollicular lymphocytes around reactive germinal centers of myoepithelial sialadenitis. Seventeen of the 21 B-cell lymphomas were positive for bcl-2, and were composed of mucosa-associated lymphoid tissue (MALT), centrocytic, centroblastic-centrocytic and centroblastic lymphomas. Noticeably, all 11 cases of MALT lymphoma were bcl-2 positive. In contrast, staining for bcl-2 was present in only one of four cases of T-cell lymphomas and was negative in one true histiocytic lymphoma. The expression of bcl-2 protein was also investigated in the ductal systems and epimyoepithelial islands of salivary glands from patients with malignant lymphoma and myoepithelial sialadenitis. While salivary ducts in eight of 15 cases of myoepithelial sialadenitis immunostained for bcl-2, epimyoepithelial islands showed bcl-2 expression in only five cases of myoepithelial sialadenitis. We found that ductal cells in the salivary gland from patients with primary non-Hodgkin's lymphomas expressed bcl-2 protein. It was of interest that epimyoepithelial islands in all cases of MALT lymphoma displayed bcl-2 expression whereas other subtypes of B-cell lymphoma, T-cell lymphoma and true histiocytic lymphoma were invariably negative. These results indicate that bcl-2 is expressed in a wide variety of non-Hodgkin's lymphomas, especially when all 11 cases of MALT lymphoma are bcl-2 positive. Epimyoepithelial islands in MALT lymphoma express this oncoprotein, and their ability to induce bcl-2 synthesis resulted in the prevention of apoptosis and prolonged cell survival. Furthermore, the expression of bcl-2 protein in the lymphoma cells may be responsible for the induction of bcl-2 expression in the adjacent epimyoepithelial islands through a lymphocyte chemical mediator.

Low-grade B cell lymphoma of mucosa-associated lymphoid tissue in the thymus of a patient with rheumatoid arthritis

The majority of thymic lymphomas are either lymphoblastic lymphoma, large B cell lymphoma or Hodgkin's disease, and other types of non-Hodgkin lymphoma are rare. A case of low-grade B cell lymphoma of mucosa-associated lymphoid tissue (MALT) in the thymus is reported. A 55-year-old Japanese female with a history of rheumatoid arthritis (RA) complained of back pain. A mediastinal tumor was identified by computerized tomography and magnetic resonance imaging, and the thymus was resected through median sternotomy. The solid and nodular tumor had several small satellite extensions and was completely confined to within the thymus. Histologically, monotonous medium-sized centrocyte-like cells occupied the medulla of the thymus and infiltrated Hassall's corpuscles (lymphoepithelial lesions). Immunohistochemically, tumor cells were positive for CD20 and CD79a. IgA and kappa light chain restriction were also found in plasmacytoid cells in the tumor. Clonal rearrangement of the immunoglobulin heavy chain gene was demonstrated by polymerase chain reaction. This case was diagnosed as MALT-type low-grade B cell lymphoma in the thymus. This is the first report of low-grade B cell lymphoma in the thymus associated with RA. As autoimmune diseases are known to be associated with lymphoid neoplasms, it is suggested that the RA played an important role in the development of malignant lymphoma in this case.

Changes in Bcl-2 and p53 expression in recurrent B-cell lymphomas

The aim of this study was to investigate the changes involved in the evolution of nine cases of recurrent B-cell lymphomas. Using the polymerase chain reaction (PCR) on formalin-fixed, paraffin-embedded tissue from both the primary and the recurrent lymphoma of each case, monoclonality was demonstrated in every tumour. In all nine cases, the recurrent lymphoma was shown to belong to the same clone as the primary lymphoma. Eight of these cases were then investigated by immunohistochemistry for changes in Bcl-2 and p53 expression. Five out of eight of the primary lymphomas showed Bcl-2 overexpression. Two of the three cases initially negative for Bcl-2 expression became positive in the recurrence. One out of eight of the primary lymphomas was positive for p53 expression. Of the seven negative cases, one became positive for p53 expression in the recurrence. Both of the p53-positive cases showed high-grade histology. This study shows that Bcl-2 overexpression is probably an important early event in the development of B-cell lymphomas, although it may occur as a post-neoplastic event. p53 mutation is probably more important as a late event and may be associated with high-grade transformation.

Immunological and molecular classification of mucosa-associated lymphoid tissue lymphoma

Malignant B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type is now considered to be a tumor of marginal zone cells of native or, more frequently, acquired MALT. The relationship of MALT lymphoma to the normal counterpart population is acknowledged by the revised European-American classification of lymphoid neoplasms (R.E.A.L.). It fits into the extranodal subtype of marginal zone lymphoma listed as a distinct entity in this recent classification scheme. A typical feature of this lymphoma type is a close lymphocyte-epithelium interaction as reflected by lymphoepithelial lesions. The immunophenotype is characterized by the expression of Sig and B-cell-associated antigens and by the lack of CD5 and CD10. Frequent occurrence of trisomy 3 has been reported. There is now overwhelming evidence that low-grade MALT lymphomas are subject to immunologic drive. In the stomach, the presence of Helicobacter pylori and locally activated T cells appears to be critical for the growth of neoplastic cells. This finding is of clinical significance since the eradication of H. pylori has been shown to reverse low-grade MALT lymphoma.

Clinicopathologic study of primary gastric lymphoma of B cell phenotype with special reference to low-grade B cell lymphoma of mucosa-associated lymphoid tissue among the Japanese

Resection specimens from 83 patients with primary gastric lymphoma (PGL) of B cell phenotype at stage IE and at stage IIE according to the Ann Arbor classification were investigated. Histologically, these lymphomas could be divided into four types: Type I lesions (n = 24) were entirely made up of MALT lymphoma; Type II lesions (n = 13) were predominantly MALT lymphoma containing one to a few foci of high-grade B cell lymphoma; Type III lesions (n = 22) consisted largely of high-grade lymphoma with small areas of low-grade MALT lymphoma; and Type IV lesions (n = 24) were pure high-grade B cell lymphoma, mostly of the large cell type. All patients had undergone primary gastric resection, and 14 received additional chemotherapy (n = 12), or both chemotherapy and radiotherapy (n = 2). The survival probability was significantly higher for Types I and II lymphomas than for Types III and IV tumors (P < 0.05 by the generalized Wilcoxon test). According to The General Rules for the Gastric Cancer Study by the Japanese Research Society for Gastric Cancer, the stage of disease showed a clear distinction between each of them (P < 0.01 by the generalized Wilcoxon test). This staging method seemed to serve well as a prognostic indicator. The histological typing of the PGL of the present series also seemed to correlate with the gross appearance, pathologic stage and prognosis. Furthermore, the expression of cyclin D1, bcl-2 and p53 protein, and PCNA was immunohistochemically investigated in 42 cases of the present series. Most of the low-grade PGL (Types I and II) had less than 60% PCNA-positive cells, whereas the high-grade PGL (Types III and IV) had more than 60% positive cells. In a study for cyclin D1 protein, no cases showed the nuclear staining pattern characteristic for mantle cell lymphoma, and the cytoplasmic staining frequently observed in the node-based large B cell lymphoma was seldom identified in the PGL. This discrepancy might suggest a lineage difference among the morphologically similar, but site-different, lymphomas. On the other hand, bcl-2 protein overexpression was almost equal in frequency between the gastric and node-based high-grade B cell lymphomas. This is in contrast to the reports from Western countries, in which the majority of high-grade gastric tumors were bcl-2 negative.

Immunohistochemical detection of p53 and Bcl-2 proteins in Hashimoto's thyroiditis and primary thyroid lymphomas

AIMS

To investigate whether immunohistochemical staining using p53 and/or bcl-2 distinguishes between florid Hashimoto's thyroiditis and low grade mucosa associated lymphoid tissue (MALT) lymphoma of the thyroid.

METHODS

Ten cases of Hashimoto's thyroiditis and eight of primary thyroid lymphoma were stained with monoclonal antibodies directed against p53 and bcl-2.

RESULTS

In Hashimoto's thyroiditis most small lymphoid cells in mantle zones, within the thyroid parenchyma and in lymphoepithelial lesions expressed bcl-2 protein. Very occasional centroblasts in reactive germinal centres were positive for p53, but all other lymphoid cells from cases of Hashimoto's disease were negative for p53. In diffuse, low grade lymphomas bcl-2 protein was uniformly expressed by most tumour cells. However, low grade lymphomas with a follicular pattern did not express bcl-2. The diffuse, low grade lymphomas were negative for p53, while occasional larger cells in the follicular subtype were positive. Both high grade lymphomas were bcl-2 negative but strongly p53 positive.

CONCLUSIONS

This study indicates that there is an inverse correlation between p53 and bcl-2 immunostaining in thyroid lymphomas (low grade lymphomas: bcl-2 positive, p53 negative; high grade lymphomas: bcl-2 negative, p53 positive). Furthermore, immunohistochemical staining for bcl-2 and p53 proteins does not distinguish florid Hashimoto's thyroiditis from diffuse, low grade thyroid lymphoma.