First application of the Automated QUantitative Analysis (AQUA) technique to quantify PTEN protein expression in ovarian cancer: A correlative study of NCIC CTG OV.16.

BACKGROUND: Platinum resistance is a dominant cause of poor outcomes in advanced ovarian cancer (OC). A mechanism of platinum resistance is the inhibition of apoptosis through phosphatidylinositol 3 kinase (PI3K) pathway activation. The role of phosphatase and tensin homolog (PTEN), a negative regulator of this pathway, as a tumor biomarker is unclear. Quantitative analysis of PTEN expression as an alternative to immunohistochemistry has not been considered. PATIENTS AND METHODS: In 238 patient tumors from the NCIC-CTG trial OV.16, PTEN protein expression was quantified by Automated QUantitative Analysis (AQUA). Cox model was used to study the association between PTEN expression and clinical outcomes using a minimum p-value approach in univariate analysis. Multivariate analysis was used to adjust for clinical and pathological parameters. RESULTS: PTEN scores (range 13.9-192.3) of the 202 samples that passed quality control were analyzed. In univariate analysis, there was a trend suggesting an association between PTEN expression by AQUA as a binary variable (low ≤61 vs high >61) and progression free survival (HR=0.77, p=0.083), and in multivariate analysis, this association approached significance (HR=0.74, p=0.059). The relationship between quantitative PTEN expression and PFS differed (p=0.01 for interaction) by the extent of surgical debulking (residual disease (RD) <1cm or ≥1cm), with a numerically superior PFS in patients with high PTEN (23.5 vs 14.9m) only when RD<1cm (p=0.19). There was no association between PTEN levels and overall survival. CONCLUSIONS: AQUA is a novel method to measure PTEN expression. Further study of PTEN as a biomarker in OC is warranted.

Improved technique for fluorescence in situ hybridisation analysis of isolated nuclei from archival, B5 or formalin fixed, paraffin wax embedded tissue.

Fluorescence in situ hybridisation (FISH) is an effective method to detect chromosomal alterations in a variety of tissue types, including archived paraffin wax embedded specimens fixed in B5 or formalin. However, precipitating fixatives such as B5 have been known to produce unsatisfactory results in comparison with formalin when used for FISH. This study describes an effective nuclear isolation and FISH procedure for B5 and formalin fixed tissue, optimising the nuclear isolation step and nuclei pretreatments using tonsil and mantle cell lymphoma specimens. The protocol presented can be used to isolate nuclei and perform FISH on B5 or formalin fixed, paraffin wax embedded samples from a variety of tissue types.

The leukemogenic transcription factor E2a-Pbx1 induces expression of the putative N-myc and p53 target gene NDRG1 in Ba/F3 cells.

The chimeric transcription factor E2a-Pbx1 is expressed as a result of the 1;19 chromosomal translocation in some 5% of cases of pediatric acute lymphoblastic leukemia. We investigated the biological and transcriptional consequences of forced expression of E2a-Pbx1 in the interleukin-3 (IL-3) dependent, bone marrow-derived cell line Ba/F3. We show that forced expression of E2a-Pbx1 induces apoptosis in Ba/F3 cells without apparent effects on cell cycle progression. This pro-apoptotic effect is enhanced on cytokine deprivation. Furthermore, using cDNA representational difference analysis (RDA), we show that these cellular effects are associated with marked induction of the gene NDRG1, which was previously identified as a target of transcriptional repression by N-myc and induction by the tumor suppressor protein p53. We identify a portion of the NDRG1 promoter capable of mediating transcriptional induction by E2a-Pbx1 and show that NDRG1 is also induced on simple IL-3 deprivation of BaF3 cells. Although we show that E2a-Pbx1 induction of NDRG1 is not impaired as a result of targeting p53 using HPV E6, and therefore does not appear to be p53-dependent, our results overall are consistent with the notion that induction of NDRG1 by E2a-Pbx1 may represent part of an apoptotic or cytostatic cellular response to oncogene activation.

Role for homodimerization in growth deregulation by E2a fusion proteins.

The oncogenic transcription factor E2a-Pbx1 is expressed in some cases of acute lymphoblastic leukemia as a result of chromosomal translocation 1;19. The early observation that E2a-Pbx1 incorporates transcriptional activation domains from E2a and a DNA-binding homeodomain from Pbx1 inspired a model in which E2a-Pbx1 promotes leukemogenic transformation of lymphoid progenitor cells through transcriptional induction of target genes defined by the Pbx1 portion of the molecule. However, the subsequent demonstration that the only known DNA-binding module on the molecule, the Pbx1 homeodomain, is dispensable for the induction of lymphoblastic lymphoma in transgenic mice called into question the contribution made by the Pbx1 portion. In this study, we have used a domain swap approach coupled with a fibroblast-based focus formation assay to evaluate further the requirement for PBX1-encoded peptide elements in growth deregulation by E2a-Pbx1. No impairment of focus formation was observed when the entire Pbx1 portion was replaced with DNA-binding/dimerization domains derived from yeast transcription factor GAL4 or GCN4. Furthermore, replacement of Pbx1 with tandem FKBP domains that mediate homodimerization in the presence of a synthetic ligand led to striking growth deregulation exclusively in the presence of the dimerizing agent. N-terminal elements encoded by E2A, including the AD1 transcriptional activation domain, were required for dimerization-induced focus formation. We conclude that transcriptional target genes defined by heterologous C-terminal DNA-binding modules are not required in growth deregulation by E2a fusion proteins. We speculate that interactions between N-terminal E2a elements and undefined proteins that could function as components of a transcriptional coactivator complex may be more important.

Restricted expression of E2A protein in primary human tissues correlates with proliferation and differentiation.

E2A is a basic helix-loop-helix (bHLH) transcription factor required for B cell lymphopoiesis and implicated in myogenesis and the regulation of insulin expression. As E2A is expressed widely in tissues, tissue-specific downstream effects are thought to result primarily from dimerization with other bHLH proteins. To investigate the degree to which regulation of E2A protein abundance may serve to regulate E2A function, expression of E2A was evaluated using immunohistochemistry on histological sections of primary human tissues. Somewhat surprisingly, nuclear staining for E2A was restricted in all tissues examined, often to a small subpopulation of cells. In some tissues, such as adult liver, expression was absent or limited to rare infiltrating lymphocytes. E2A-expressing cells were most abundant in lymphoid tissues. In tonsil, lymph node, and spleen, expression appeared most abundant and prevalent among rapidly proliferating centroblasts of the germinal center dark zone. Scattered E2A-expressing thymocytes were more numerous in the thymic cortex than medulla. In developing skeletal muscle, E2A was detectable in striated myotubes but not in more primitive mononucleated progenitors or mature muscle. Differential E2A expression was also noted in proliferating periventricular neuroepithelial cells in the developing brain. These results suggest that regulation of E2A abundance complements protein-protein interactions in modulating E2A function.

Congenital erythroleukemia in a neonate with severe hypoxic ischemic encephalopathy.

We report a case of a neonate who presented with hypoxic ischemic encephalopathy, persistent hypoglycemia and hypotension, intractable metabolic acidosis, renal failure and a coagulopathy but who, at autopsy, was found to have massive infiltration of nonhematopoietic tissues with blasts. The diagnosis of congenital erythroleukemia was confirmed by the detection of glycophorin A, a major erythrocyte membrane protein, on the surface of the blasts. The clinical presentation and course of the case described here have not previously been reported for this extremely rare condition.

The chimeric oncoproteins E2A-PBX1 and E2A-HLF are concentrated within spherical nuclear domains.

Oncogenic mutation of nuclear transcription factors often is associated with altered patterns of subcellular localization that may be of functional importance. The leukemogenic transcription factor gene E2A-PBX1 is created through fusion of the genes E2A and PBX1 as a result of t(1;19) in acute lymphoblastic leukemia. We evaluated subcellular localization patterns of E2A-PBX1 protein in transfected cells using immunofluorescence. Full-length E2A-PBX1 was exclusively nuclear and was concentrated in spherical domains denoted chimeric-E2A oncoprotein domains (CODs). In contrast, nuclear fluorescence for wild-type E2A or PBX1 proteins was diffuse. Enhanced concentrations of RNA polymerase II within many CODs and the requirement for an E2A-encoded activation domain suggested transcriptional relevance. However, in situ co-detection of nascent transcripts labeled with bromouridine failed to confirm altered transcriptional activity in relation to CODs. CODs also failed to co-localize with other proteins known to occupy functional nuclear compartments, including the transcription factor PML, the spliceosome-associated protein SC-35 and the adenovirus replication factor DBP, or with foci of DNA replication. Co-transfection of Hoxb7, a homeodomain protein capable of enhancing DNA binding by PBX1, impaired COD formation, suggesting that CODs contain E2A-PBX1 protein not associated with DNA. We conclude that, as a 'gain of function' phenomenon requiring protein elements from both E2A and PBX1, COD formation may be relevant to the biology of E2A-PBX1 in leukemogenesis.

Interleukin-6 is required for pristane-induced plasma cell hyperplasia in mice.

Intraperitoneal injection of pristane induces production of interleukin-6 (IL-6) and either plasmacytosis or plasmacytoma in mice, depending upon the genetic background. Pristane does not induce plasmacytoma in IL-6 knockout (IL-6-/-) mice, suggesting that IL-6 is required for this process. In the present study we determined whether IL-6 is also required for pristane-induced hyperplasia of normal plasma cells. Pristane was injected intraperitoneally into IL-6-/- and IL-6 wild-type (IL-6+/+) mice. Overall there were more deaths in IL-6+/+ mice (85%) than in IL-6-/- mice (40%), P = 0.024. Hyperplastic lymph node and spleen weight did not differ (P = 0.82 and P = 0.15, respectively) in IL-6-/- versus IL-6+/+ mice. Lymphocytosis with similar patterns of expression of B-cell (B220) and T-cell (Thy-1) antigens was noted in both IL-6-/- and IL-6+/+ mice. However, morphological studies, dual fluorescent staining for Syn-1 and B220 antigens (syn-1+ B220+ cells), and intracytoplasmic Ig staining revealed plasma cell hyperplasia in lymph node and spleen from IL-6+/+, but not IL-6-/-, mice. These plasma cells from IL-6+/+ mice were polyclonal and unable to induce tumour formation in severe combined immunodeficient mice. These data demonstrate that IL-6 is required for pristane-induced hyperplasia of polyclonal plasma cells in mice.

bcl-2 expression in primary malignancies of the skin.

BACKGROUND AND DESIGN: Basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and malignant melanoma (MM) are the three most common malignant neoplasms that arise in the skin. Deregulation of oncogene function not infrequently leads to an increased rate of cellular proliferation. However, the expansion of malignant cells can also occur if programmed cell death is inhibited. The oncogene bcl-2 participates in the regulation of apoptosis (programmed cell death). In view of this, we determined the presence and possible role of bcl-2 in primary cutaneous malignancies. Routine paraffin sections of formalin-fixed BCCs, SCCs, MMs (primary and metastatic), actinic keratoses, and SCCs in situ were labeled with anti-bcl-2 monoclonal antibody using a biotin-avidin-immunoperoxidase procedure. RESULTS: Twenty-three BCCs were examined and all expressed cytoplasmic bcl-2. Two of 20 SCCs were positive. One of these had patchy, diffuse staining, and the other stained in only small foci. None of eight SCCs in situ and none of eight actinic keratoses expressed bcl-2. Sixteen of 18 MMs expressed bcl-2. CONCLUSIONS: The bcl-2 gene product has been found to inhibit apoptosis. Our preliminary results suggest that the expression of bcl-2 is present quite consistently in BCCs and MMs, but not in SCCs or precursor lesions. The expression (or lack thereof) of bcl-2 may reflect the difference in the regulation of cell turnover between these tumors, or histogenetic differences.

Transformation properties of the E2a-Pbx1 chimeric oncoprotein: fusion with E2a is essential, but the Pbx1 homeodomain is dispensable.

The t(1;19) chromosomal translocation in acute lymphoblastic leukemias creates chimeric E2a-Pbx1 oncoproteins that can act as DNA-binding activators of transcription. A structural analysis of the functional domains of E2a-Pbx1 showed that portions of both E2a and Pbx1 were essential for transformation of NIH 3T3 cells and transcriptional activation of synthetic reporter genes containing PBX1 consensus binding sites. Hyperexpression of wild-type or experimentally truncated Pbx1 proteins was insufficient for transformation, consistent with their inability to activate transcription. When fused with E2a, the Pbx-related proteins Pbx2 and Pbx3 were also transformation competent, demonstrating that all known members of this highly similar subfamily of homeodomain proteins have latent oncogenic potential. The oncogenic contributions of E2a to the chimeras were localized to transactivation motifs AD1 and AD2, as their mutation significantly impaired transformation. Either the homeodomain or Pbx1 amino acids flanking this region could mediate transformation when fused to E2a. However, the homeodomain was not essential for transformation, since a mutant E2a-Pbx1 protein (E2a-Pbx delta HD) lacking the homeodomain efficiently transformed fibroblasts and induced malignant lymphomas in transgenic mice. Thus, transformation mediated by the chimeric oncoprotein E2a-Pbx1 is absolutely dependent on motifs acquired from E2a but the Pbx1 homeodomain is optional. The latter finding suggests that E2a-Pbx1 may interact with cellular proteins that assist or mediate alterations in gene expression responsible for oncogenesis even in the absence of homeodomain-DNA interactions.

Lymphoid neoplasms in patients with rheumatoid arthritis and dermatomyositis: frequency of Epstein-Barr virus and other features associated with immunosuppression.

We recently reported two cases of reversible Epstein-Barr virus (EBV)-associated lymphomas in patients undergoing methotrexate therapy for rheumatic disease. The current study was undertaken to investigate how frequently lymphoid neoplasms in patients with rheumatic disease show features of lymphoproliferations occurring in immunocompromised patients. Eighteen patients (including the two previously reported patients) with rheumatoid arthritis or dermatomyositis who developed lymphoproliferative lesions and on whom detailed clinical information was available were studied. As a group these patients developed a spectrum of lymphoproliferative lesions; however, a subset of patients developed neoplasms with features associated with immunosuppression. The neoplasms occurred in extranodal sites in 10 (56%) patients, showed a diffuse large-cell histology in nine (50%) patients, and contained EBV (EBER1) transcripts and EBV latent membrane protein in six (33%) patients. In three (17%) patients the neoplasms showed the entire constellation of features typical of immunosuppression-associated lymphoproliferations, including extranodal location, large-cell or polymorphous histology, geographic areas of necrosis, and the presence of EBV. These three patients were receiving both steroids and methotrexate at the time they developed their neoplasms. The findings of this study support the hypothesis that a subset of lymphoid neoplasms in rheumatic patients occurs in an immunocompromised setting and suggest that therapeutic immunosuppression may contribute, at least in part, to the development of these lymphoid neoplasms.

Fusion with E2A alters the transcriptional properties of the homeodomain protein PBX1 in t(1;19) leukemias.

The t(1;19) chromosomal translocation is observed in pre-B cell acute lymphoblastic leukemias and results in expression of chimeric E2A-PBX1 proteins that contain transcriptional activation domains from E2A and the homeodomain of PBX1. Since homeodomains mediate DNA-binding, a potential model for the action of E2A-PBX1 is that it disrupts the transcriptional regulation of genes normally controlled by PBX1 or its closely-related family members PBX2 or PBX3. Using a binding site selection assay, we identified a consensus nucleotide sequence ATCAATCA specifically bound by the PBX1 homeodomain and those of its closely-related family members PBX2 and PBX3. An endogenous protein with the properties of PBX3b specifically bound to this sequence in nuclear extracts of precursor B cells. Transfection of reporter genes containing PBX binding sites linked to a minimal promoter demonstrated transactivation by E2A-PBX1 fusion protein dependent upon presence of the homeodomain. In contrast, wild-type PBX proteins were incapable of activating transcription. The striking differences in transcriptional properties of fusion and wild-type PBX proteins provides strong functional evidence for the importance of aberrant transcriptional regulation in the genesis of t(1;19)-bearing leukemias.

Floral variant of follicular lymphoma. Immunological and molecular studies support a neoplastic process.

In recent reports of the so-called "floral variant" of follicular lymphoma, an unusual variant of follicular lymphoma mimicking progressive transformation of germinal centers, questions have been raised regarding whether this process represents a malignant lymphoma. We studied 19 examples of the floral variant of follicular lymphoma and report our light microscopic, immunohistochemical, and molecular diagnostic findings. Morphologic changes consisted of effacement of normal lymph node architecture by follicles composed of atypical lymphocytes. The follicles were surrounded by prominent mantle zones that invaginated irregularly into the follicle centers, often imparting a "floral" appearance. Sufficient material was available for immunophenotypic or genotypic studies in 15 biopsies. Twelve of 15 cases studied by immunohistochemistry demonstrated phenotypes supporting a diagnosis of lymphoma. Five demonstrated light-chain restriction; one was an immunoglobulin-negative B-cell neoplasm; and six, in which only formalin-fixed, paraffin-embedded tissue was available, demonstrated overexpression of the bcl-2 protein. Southern blot analysis revealed evidence of clonal immunoglobulin heavy-chain gene rearrangement in all five cases tested. Overall, 12 of the 15 biopsies studied with these techniques showed immunologic or genotypic support for malignant lymphoma. The results of this study demonstrate that the floral variant of follicular lymphoma does indeed represent a malignant lymphoma.

The bcl-2 oncogene in Hodgkin's disease arising in the setting of follicular non-Hodgkin's lymphoma.

Expression of the bcl-2 proto-oncogene on chromosome 18 is deregulated by the 14; 18 chromosomal translocation, an abnormality that is consistently associated with follicular non-Hodgkin's lymphomas (NHL). Because bcl-2 is believed to function by prolonging cell survival rather than by increasing proliferation, the presence of t(14; 18) in Hodgkin's disease (HD) would have profound implications for the pathogenesis of this neoplasm. We evaluated 32 cases of HD for t(14; 18) by polymerase chain reaction (PCR). These results were correlated with expression of bcl-2 oncogenic protein by Hodgkin cells and with the presence of Epstein-Barr virus (EBV), as determined by immunohistochemistry or in situ hybridization. PCR provided evidence of t(14; 18) in only 2 HD cases (6%), both of which were associated with a prior history of follicular lymphoma, and both of which were among the 7 cases (22%) with strong bcl-2 expression in Hodgkin cells. In at least 1 of the cases, the translocation involved identical chromosomal breakpoints in both types of lymphoma. Furthermore, 7 additional cases of combined follicular NHL and HD showed strong bcl-2 staining in Hodgkin cells. Although EBV was detected in 6 of 30 cases, it was not associated with t(14; 18) and usually not with strong bcl-2 expression. These results suggest that a small proportion of HD cases might evolve from follicular NHL, possibly through molecular events superimposed on the t(14; 18). High-level bcl-2 expression in Hodgkin cells is a potentially useful but not definitive marker for these cases.

Chimeric homeobox gene E2A-PBX1 induces proliferation, apoptosis, and malignant lymphomas in transgenic mice.

Expression of the homeobox fusion gene E2A-PBX1 under control of the immunoglobulin heavy chain enhancer efficiently induced malignancies in transgenic mice. All animals died before 5 months of age with lymphomas that demonstrated phenotypes consistent with transitional intermediate thymocytes (CD4+/CD8+/CD3med). E2A-PBX1 also markedly altered lymphoid development in pretumorous animals, reducing the number of thymocytes and bone marrow B lineage progenitors to 20% of normal levels. In spite of the observed reductions in lymphoid cells, premalignant animals contained significantly increased numbers of cycling thymocytes, but a higher proportion was also undergoing apoptosis, suggesting that increased cell death resulted in the marked lymphopenias. These data indicate that the chimeric homeodomain protein E2A-PBX1 paradoxically induces both proliferation and apoptosis in lymphoid cells, suggesting an in vivo association between nuclear oncogene-induced cell cycle progression and programed cell death.

Expression of bcl-2 in fetal tissues suggests a role in morphogenesis.

We have studied the distribution of the bcl-2 protein in fetal tissues, in an effort to uncover patterns of expression that may elucidate the potential role of bcl-2 during development. We find that bcl-2 is expressed in many hematolymphoid and non-hematolymphoid tissues, most abundantly in placental trophoblast. In tissues of endocrine and neural derivation and in stem-cell populations of colonic and some stratified epithelia, bcl-2 seems to be involved in tissue homeostasis. However, in developing proximal nephrons of the kidney and other sites characterized by inductive interactions between epithelium and mesenchyme, bcl-2 is apparently involved in morphogenesis, possibly by mediating the formation of condensations of cells that are "committed" to the formation of more differentiated structures. The distribution of bcl-2-protein expression in fetal tissues is consistent with its previously described role in promoting cell survival, presumably by preventing apoptosis in lymphoid and other tissues where cell death represents an active regulatory process. Expression of bcl-2 protein is more widespread in fetal than adult tissues. Our observations therefore represent supportive evidence for the importance of inducible cell survival as a regulatory process in normal homeostasis and morphogenesis in many fetal tissues and structures.

Topographical dissociation of BCL-2 messenger RNA and protein expression in human lymphoid tissues.

Immunohistochemistry and in situ hybridization with a synthetic oligonucleotide probe were used to compare the topographical distribution of BCL-2 proto-oncogenic protein with that of its messenger RNA (mRNA) in normal lymphoid tissues, follicular lymphomas, and lymphoma-derived cell lines. In normal lymph nodes, BCL-2 protein was most abundant in the small lymphocytes of primary lymphoid follicles and the mantle zones of secondary follicles, virtually absent within germinal centers, and of variable abundance in many interfollicular cells. In contrast, the distribution of BCL-2 mRNA was roughly reciprocal to that of the protein with intense hybridization signal in germinal centers and almost none in mantle zones. Discordant BCL-2 RNA and protein levels were also observed in tonsillar epithelial cells and cortical thymocytes. Concordant and abundant expression of BCL-2 mRNA and protein was detected in biopsy tissues and cell lines from t(14;18)-carrying lymphomas. The contrasting distributions of BCL-2 protein and RNA in normal lymphoid tissues suggest that translational and posttranslational control mechanisms play a significant role in regulating BCL-2 protein levels in germinal center cells, epithelial cells, and cortical thymocytes. Concordant BCL-2 mRNA and protein levels in follicular lymphomas suggest that translational control mechanisms may be disrupted as part of the sequence of genetic changes that transforms normal lymphoid cells into neoplastic follicular lymphoma cells.

Estimation of tumor growth fractions in archival formalin-fixed, paraffin-embedded tissues using two anti-PCNA/Cyclin monoclonal antibodies. Factors affecting reactivity.

Immunohistochemical detection of cell cycle-related markers for estimation of tumor growth fractions using paraffin-embedded tissue sections would have applications in experimental and clinical pathology as an in situ histologic alternative to flow cytometry. The monoclonal antibodies 19A2 and PC10 detect the proliferating cell nuclear antigen (PCNA/Cyclin), an auxiliary protein to DNA polymerase-delta. In a prospective group of uniformly handled, formalin-fixed malignant lymphomas we previously demonstrated 19A2 to be a reliable marker of proliferative activity similar to Ki-67 in frozen tissue. The present study examines the applicability of this technique in archival formalin-fixed material. Studies on tonsilar tissue revealed that formalin fixation beyond 30 hours adversely affected reactivity of 19A2, possibly explaining the variable results in nonuniformly fixed archival material. We found that only 27 (56%) of 48 archival cases of infiltrating ductal carcinoma showed sufficient reactivity with 19A2 to permit reliable quantification of the tumor growth fraction. Acid pretreatment with 2N HCl had no apparent effect on 19A2 reactivity. Using both antibodies on a group of 32 archival lymphomas, carcinomas, and sarcomas, significantly more biopsies stained reliably for PC10 (84%) than for 19A2 (72%; P < 0.036). Further, none of the cases that did not react with PC10 reacted with 19A2. PC10 may recognize a different epitope of PCNA/Cyclin which may be more resistant to alterations by fixation. In the 23 cases that reliably stained for both markers, largely carcinomas, there was excellent correlation between estimated growth fractions (r = 0.96). Although immunostaining provides a useful way to estimate tumor growth fractions in paraffin-embedded tissues, modifications of technique and cautious interpretation of results are advisable when using archival material.

Follicular lymphomas of the gastrointestinal tract. Pathologic features in 31 cases and bcl-2 oncogenic protein expression.

The gastrointestinal tract is the most common site for extranodal lymphomas, but follicular lymphomas involving the gut are rare. To study their pathologic features and bcl-2 expression, 31 follicular lymphomas of the GI tract were reviewed and unstained paraffin sections from 24 of the cases were immunohistochemically stained using a monoclonal antibody for the peptide product of the proto-oncogene bcl-2. The most common site of lymphoma involvement was the small intestine, especially the terminal ileum. Gastric lymphomas tended to present clinically with symptomatic ulcers and small intestinal lesions presented with obstruction. Five cases involving the terminal ileum or colon had a gross appearance of multitudinous mucosal polyps and were considered to represent examples of "multiple lymphomatous polyposis." Enhanced expression of the bcl-2 oncogenic protein was detectable in lymphoma cells in 75% of cases and at lower levels in normal lymphoid cells in most cases. Small cleaved or mixed cell lymphomas were more likely to show enhanced expression than were large cell cases. Reactive germinal centers showed no bcl-2 staining. It is concluded that follicular GI lymphomas are associated with distinctive pathological features. In their tendency to express bcl-2, these neoplasms resemble their lymph node-based counterparts. Immunohistochemical staining for enhanced bcl-2 expression is of potential diagnostic utility in distinguishing between follicular lymphoma and follicular lymphoid hyperplasia in the gastrointestinal tract. The relevance of the results to lymphoma of mucosa-associated lymphoid tissue (MALT) is discussed.

Warthin-Finkeldey polykaryocytes demonstrate a T-cell immunophenotype.

Warthin-Finkeldey polykaryocytes have been described in various benign and malignant lymphoid conditions since their initial identification in tonsils of patients in the prodromal stage of measles. However, the nature of these multinucleated giant cells is obscure. The authors studied the immunohistochemical profile of the Warthin-Finkeldey-type giant cells in three cases of lymphoid proliferations (two reactive, one neoplastic) containing many multinucleated cells using a panel of paraffin-reactive antibodies. Warthin-Finkeldey polykaryocytes demonstrated reactivity with Leu22 (CD43), anti-CD3, and OPD4, indicating that these cells are multinucleated T lymphocytes. The significance of these results with respect to the disorders in which these cells are found and their possible role in pathogenesis of disease are discussed.