The histological diagnosis of toxoplasmic lymphadenitis

Toxoplasma Lymphadenopathy in an Immunocompetent Host

Toxoplasma infection can be congenital or acquired. Infection with <i>Toxoplasma gondii</i> can result in multi-organ involvement in immunocompromised patients; whereas in immunocompetent patients, it usually remains asymptomatic. <i>Toxoplasma</i> is a rare cause of isolated lymphadenopathy especially in immunocompetent individuals, though it is a common manifestation of this protozoal infection. We present a 27-year-old male who presented to us with isolated cervical lymphadenopathy. Histopathology and serological studies confirmed the diagnosis of toxoplasma lymphadenopathy. It usually affects the posterior cervical group of lymph nodes, but in our case, it had also affected anterior group and presented without any constitutional symptom. The patient was treated with cotrimoxazole double strength tablet once daily for 1 month and responded well.

Toxoplasmic Lymphadenitis Presenting as a Tiny Neck Tumor

(1) Background: Toxoplasmic lymphadenitis (TL), caused by the protozoan Toxoplasma gondii, is a worldwide zoonosis. We report a case of TL in the head and neck region diagnosed using ultrasound (US)-guided fine needle aspiration cytology (FNAC), serological tests, and pathological findings. (2) Case Presentation: A 51-year-old female with a chief complaint of a left posterior neck mass that had been growing for approximately 2 weeks. TL was confirmed by histopathological examinations and serological tests. US-guided FNAC and en bloc resection of the lymph node were performed. The diagnosis was confirmed as TL in the neck. (3) Conclusions: We suggest that US-guided FNAC should be considered as the first-line test for assessing a tiny mass before a definitive treatment is chosen.

Toxoplasma cyst detection in Piringer-Kuchinka lymphadenitis. Report of two cases and literature review

The diagnosis of acute toxoplasmic lymphadenitis is traditionally based on the combination of lymph node excisional biopsy with specific tests. The classic triad (marked follicular hyperplasia, small irregular clusters of epithelioid histiocytes in germinal centers, and sinusoidal distension by monocytoid B lymphocytes) is considered diagnostic of the so-called Piringer-Kuchinka lymphadenitis. Toxoplasma gondii organisms have been exceptionally disclosed in such histopathological setting, establishing the diagnosis of toxoplasmic lymphadenitis. Two cases of Piringer-Kuchinka lymphadenitis with toxoplasma cyst demonstration are reported, along with a complete review of the literature.

New-Onset Cervical Lymphadenopathy in a Patient Undergoing Treatment of Pulmonary Mycobacterium avium Complex Infection: Toxoplasmosis Lymphadenitis

Immunocompetent hosts with toxoplasmosis are usually asymptomatic. However, T. gondii can present as an acute systemic infection. Symptomatic patients usually have a benign, self-limited course that typically lasts from a few weeks to months. Herein, we present a 66-year-old immunocompetent female who developed dysphagia and new-onset cervical lymphadenopathy during pulmonary Mycobacterium avium complex treatment.

Diagnostic Cell Pathology in Lymph Nodes Diseases

The investigation is based on the cytological findings in imprints, stained by the modified Papanicolaou E.A. 50 method, of 190 lymph nodes, of which 10 were normal 60 with benign diseases, 58 with malignant lymphomas and 62 with metastases. The cytological data were controlled by and correlated with histological sections. Touch preparations of lymph nodes do not present technical difficulties, are rapidly prepared and are always satisfactory. Cytological details are much better preserved and more recognizable than in histological sections but little information on lymph node organization is yielded. Imprints do not replace tissue diagnoses or even frozen sections, but under certain circumstances they may supply sufficient data for immediate diagnostic purposes, such as findings of metastatic malignant tumor cells or of Reed-Sternberg cells and their variants in lymph nodes during laparatomy for the staging of Hodgkin's disease. In addition to their supplementary diagnostic as well as teaching value, touch preparations allow minute caryological observations in malignant lymphomas. Peculiar basic nuclear structures in both well and poorly differentiated lymphocytic lymphomas and two different nuclear types in histiocytic lymphoma are described. The variations and frequency of several cell types (reticulum cells, lymphocytes, histiocytes, Reed-Sternberg and lacunar cells) in Hodgkin's disease are described and correlated with the histologic type.

Toxoplasmosis submandibular lymphadenitis: Report of an unusual case with a brief review

A 16-year-old male patient reported with swelling of the right submandibular region for 3 months. The patient was asymptomatic and gave a history of fever lasting for 2 days before observing the swelling. Fine-needle aspiration cytology revealed nonspecific lymphadenitis, and since there was no apparent cause detected in the oral cavity or any systemic condition noted, the enlarged lymph node was surgically excised and submitted for histopathologic examination. The inflammatory condition and large numbers of macrophages appeared nonspecific while granuloma formation was not seen. Specific antibody titer against Toxoplasma gondii was carried out and extremely high level of IgG for toxoplasma was detected confirming the diagnosis of toxoplasmosis leading to lymphadenitis.

Granulomatous lymphadenitis

In this review, representative types of granulomatous lymphadenitis (GLA) are described. GLA can be classified as noninfectious GLA and infectious GLA. Noninfectious GLA includes sarcoidosis and sarcoid-like reaction. The cause of sarcoidosis remains unknown, but it has good prognosis. Sarcoid-like reaction, which is considered to be a biological defense mechanism, is observed in regional lymph nodes with many underlying diseases. Infectious GLA can be classified as suppurative lymphadenitis (LA) and nonsuppurative LA. Suppurative LA generally shows follicular hyperplasia and sinus histiocytosis in the early phase. In tularemia and cat scratch disease, monocytoid B lymphocytes (MBLs) with T cells and macrophages contribute to the formation of granuloma. However, none of the epithelioid cell granulomas of Yersinia LA contains MBLs like in cat scratch disease. In addition, almost all have a central abscess in granulomas induced by Gram-negative bacteria. In terms of the lymph nodes, tularemia and cat scratch disease are apt to affect the axillary and cervical regions while Yersinia LA affects the mesenteric lymph node. Nonsuppurative LA includes tuberculosis and BCG-histiocytosis. These are induced by delayed allergic reaction of M. tuberculosis. Tuberculosis LA mainly appears in the cervical lymph node. Organisms are histologically detected by Ziehl-Neelsen staining in the necrotic area. Toxoplasmosis is also a nonsuppurative protozoan infection (Toxoplasma gondii). In toxoplasma LA, MBLs can also be seen, but round and organized, well-formed granulomas are not found in this disease. Furthermore, necrosis is not induced and there are no accompanying neutrophils, eosinophils and fibrosis. GLA described above is associated with characteristic histological findings. An accurate pathological diagnosis using the above findings can lead to precise treatment.

BCL-2 is consistently expressed in hyperplastic marginal zones of the spleen, abdominal lymph nodes, and ileal lymphoid tissue

BCL-2 is an antiapoptotic protein overexpressed in follicular lymphomas, principally as a result of the t(14;18)(q32;q21), and useful in distinguishing follicular lymphoma (usually BCL-2 positive) from follicular hyperplasia (BCL-2 negative). BCL-2 is also overexpressed in other lymphoma types without the t(14;18), including marginal zone B-cell lymphoma, because of other, poorly understood mechanisms. It has been suggested that BCL-2 immunoreactivity can distinguish between malignant (BCL-2 positive) and reactive (BCL-2 negative) marginal zone B cells. In this study, we evaluated 26 spleen, 10 abdominal lymph node, and 3 ileum specimens with marginal zone B-cell hyperplasia for BCL-2 expression immunohistochemically. We also analyzed these cases using polymerase chain reaction methods to evaluate for the presence of clonal rearrangements of the immunoglobulin heavy chain gene (IgH) using consensus V FRIII and J region primers, and the t(14;18) involving both the major breakpoint and the minor cluster regions of the bcl-2 gene. All (100%) cases of splenic, abdominal lymph node, and ileal marginal zone hyperplasia displayed strong BCL-2 reactivity in the marginal zone B cells. In all cases analyzed, IgH polymerase chain reaction demonstrated a polyclonal pattern, and bcl-2/JH DNA fusion sequences were not detected. Our results indicate that BCL-2 is consistently expressed by reactive marginal zone B cells of the spleen, abdominal lymph nodes, and ileal lymphoid tissue and should not be used as a criterion for discriminating between benign and malignant marginal zone B-cell proliferations involving these sites.

Specificity of the histopathological triad for the diagnosis of toxoplasmic lymphadenitis: polymerase chain reaction study

Toxoplasmosis is a common cause of lymphadenopathy, but toxoplasmic cysts are not usually found in histological sections used for establishing diagnosis, except on extremely rare occasions. The histopathological triad of florid reactive follicular hyperplasia, clusters of epithelioid histiocytes, and focal sinusoidal distention by monocytoid B cells has been considered to be diagnostic of toxoplasmic lymphadenitis, but the validity of the histopathological triad is based indirectly on serological correlation only. The demonstration of Toxoplasma gondii DNA in lymph nodes displaying the histopathological triad will indicate the validity of the histopathological triad as the criterion for the histopathological diagnosis of toxoplasmic lymphadenitis. We used frozen tissues of 12 lymph nodes with the histopathological triad and tissues of 27 lymph nodes from patients with various other conditions (including 13 cases of follicular lymphoid hyperplasia, FLH; three cases of dermatopathic lymphadenopathy, DPL; two cases of plasmacytosis; two cases of Castleman's disease; two cases of metastatic adenocarcinoma; and five cases of lymphoma) to detect T. gondii DNA by polymerase chain reaction. Ten out of 12 lymph nodes with the triad and six out of 27 lymph nodes without the triad were positive for T. gondii DNA. Thus, the sensitivity of the triad was 62.5% (10/16) and the specificity was 91.3% (21/23). The predictive value of positive tests was 83.3% (10/12) and the predictive value of negative tests was 77.7% (21/27). The six cases positive for T. gondii DNA without the triad were four cases of FLH, one case of DPL, and one case of plasmacytosis. None of the neoplastic diseases was positive. The false positive and negative cases could be due to sampling problems or past T. gondii infection. The results confirm that the histopathological triad is highly specific for the diagnosis of toxoplasmic lymphadenitis and can be used confidently.

Unique phenotypic profile of monocytoid B cells: differences in comparison with the phenotypic profile observed in marginal zone B cells and so-called monocytoid B cell lymphoma

Monocytoid B cells (MBCs) are a subset of B cells that may be recognized in several reactive and tumoral lymph node conditions, including toxoplasmic lymphadenitis, infectious mononucleosis, and Hodgkin's lymphoma. Although this is a commonly observed cell population, which has even given its name to a type of lymphoma, MBC lymphoma, scarcely any information is available about the function and characteristics of this cell type. A relationship with marginal zone (MZ) B lymphocytes has been claimed for MBCs, but this has not yet been fully proven. Indeed, specific markers for MBCs are still lacking, which has made it difficult to analyze their relationship with other B cell subpopulations and confirm the existence of tumors deriving from this B cell subset. We used a panel of cell cycle markers to explore the characteristics of MBCs and their relationship with MZ B cells, nodal MZ lymphoma, and splenic MZ lymphoma. We therefore compared the phenotypic profile of MBCs in different conditions with normal MZ B cells within the spleen and mesenteric lymph nodes, with a group of seven cases of nodal MZ/MBC lymphoma and another group of five cases of splenic MZ lymphoma. MBCs were mainly in the G(0) to G(1) phases, as deduced from the presence of a proportion of between 10 and 35% Ki67-positive cells, whereas very low expression was observed with cyclin A and cyclin B staining. Nests of MBCs were clearly labeled by the expression of p21(WAF1), a cyclin-dependent kinase inhibitor (CKI), rarely detectable in benign lymphocytes, and by cyclin E. Basically all MBCs were bcl-2-negative, and high cyclin D2 and cyclin D3 were also detected in these cells, at proportions and intensities above expected levels, when the percentage of proliferating cells was taken into account. p27(KIP1) expression was characterized by homogeneous reactivity, higher than that observed in other B cell populations with a relatively high-growth fraction. Immunoglobulin staining showed undetectable light and heavy chains. However, splenic MZ cells, nodal MZ lymphoma, and splenic MZ lymphoma showed a distinct expression of IgM and bcl-2, with high p27 (KIP1) nuclear expression and undetectable or low levels of cyclin A, B, E, or D, or p21(WAF1) expression. The data from this study show an unexpected immunophenotype in MBCs, different from the one observed in splenic and lymph node MZ B cells. This suggests that either MBCs are a unique B cell population from a distinct cell lineage, or if related to MZ cells, they would represent a definite differentiation stage characterized by a distinctive immunophenotype. They also show so-called MZ/MBC lymphoma to be more closely related to lymph node and splenic MZ B cells, as they do not share the most distinctive features of MBCs.

Monocytoid B Cells Are Distinct From Splenic Marginal Zone Cells and Commonly Derive From Unmutated Naive B Cells and Less Frequently From Postgerminal Center B Cells by Polyclonal Transformation

Monocytoid B cells represent a morphologically conspicuous B-cell population that constantly occurs in Toxoplasma gondii-induced Piringer’s lymphadenopathy. Although widely believed to be closely related to splenic marginal zone B cells, neither this relationship, nor the B-cell differentiation stage of monocytoid B cells, nor their cellular precursors have been established. We have therefore examined monocytoid B cells for their expression of B-cell differentiation markers and the Ig isotypes at the RNA and protein level as well as for rearranged Ig heavy chain (H) genes and somatic mutations within the variable (V) region. The results obtained were compared with the corresponding features of other B-cell populations. The monocytoid B cells displayed immunophenotypical differences to all other B-cell populations. IgM and IgD expression was absent from most monocytoid B cells at the RNA and protein levels. Unrelated (polyclonal) Ig rearrangements were found in 85 of the 95 cells studied. Seventy-four percent of the rearranged VH genes were devoid of somatic mutations, whereas the remaining 26% carried a low number of somatic mutations. The majority of these showed no significant signs of antigen selection. This finding in conjunction with the predominantly unrelated Ig gene rearrangements indicates that most monocytoid B cells arise not by clonal proliferation but by transformation of polyclonal B cells. The B cells undergoing a monocytoid B-cell transformation are in the majority (74%) naive B cells, and only a minority are (26%) non–antigen-selected postgerminal center B cells. Thus, our data show that monocytoid B cells represent a distinct B-cell subpopulation.

Marginal zone B-cell lymphomas: an appraisal

Although the Revised European-American Lymphoma Classification does not utilize the term monocytoid B-cell Lymphoma, there are numerous reasons to support its use in classifying lymphomas of so-called marginal zone B-cell type that contain a distinct population of malignant monocytoid B-cells. In addition, there are other B-cell lymphomas which have very distinctive morphological features, because they show multiple and very well demarcated histologies characterized by presence of cells that appear to be (1) malignant monocytoid B-cells and malignant follicular center cells, or (2) malignant monocytoid B-cells, malignant follicular center cells and malignant plasma cells, or (3) malignant monocytoid B-cells and malignant mantle cells. The neoplastic cells in each of the above three examples show identical light chain restriction and thus they are part of the same neoplastic clone. We believe that there are different types of precursor B-cells (memory or otherwise) for the above cells, and an arrest in differentiation of these precursor B-cells may readily explain the presence of these different morphological combinations. Recognition of these morphological types may lead to further awareness of the possibilities of the existence of multiple, linked pathways of differentiation for lymphoid cells including the possibility of different types of precursor B-cells. Furthermore, an understanding of the uniqueness of monocytoid B-cells would allow pathologists to use terminology that is less redundant and more precise.

Acquired toxoplasmosis of a submandibular lymph node in a 9-year-old boy diagnosed by fine-needle aspiration cytology

Toxoplasmosis is a parasitic infection which may be asymptomatic or produce lymphadenopathy, fever and malaise. In children the cervical lymph nodes are most commonly affected. This report describes a case of a 9-year-old boy who presented with submandibular lymphadenopathy associated with a non-vital primary tooth, which persisted following extraction of the tooth. A diagnosis of acquired toxoplasmosis was made on the findings of fine-needle aspiration cytology and subsequently confirmed by serological investigations, thus sparing the patient unnecessary hospitalization and surgery. The patient required amitryptyline as a nocturnal sedative and made a complete recovery within a few months without the need for further intervention.

INDIRECT FLUORESCENT ANTIBODY TECHNIQUE IN THE SEROLOGY OF TOXOPLASMA GONDII

The indirect fluorescent antibody technique has been used to titrate patients' antibody against Toxoplasma gondii. Rigorous tests of the immunological validity of the method were made. The reactions of the gamma globulin of human immune serum with Toxoplasma gondii and fluorescent rabbit anti-human gamma globulin were thus shown to be specific. Thereafter the technique could be used with confidence to detect the reaction between doubling dilutions of patient's serum and smears of unfixed Toxoplasma gondii. In this way, titres were obtained with the indirect fluorescent antibody technique which agreed well with those of the dye test at both low and high levels of antibody. Compared with the dye test, the indirect fluorescent antibody technique has many advantages. The end-point is sharp and obviates the counting of stained and unstained organisms; supplies of antibody-free accessory factor sera are not needed; prozones undetected by the dye test are strongly positive at screening dilutions, the reagents keep indefinitely and lend themselves to preparation, standardization, and issue by a central reference laboratory.

Value of lymph node biopsy in the diagnosis of acquired toxoplasmosis

Toxoplasmic lymphadenitis generally involves a solitary lymph node in the head and neck regions, without systemic symptoms. In order to determine the frequency of toxoplasmic lymphadenitis, we reviewed the histological sections of 731 consecutive patients with reactive lymph node hyperplasia. Amongst 731 patients, 112 had histological features supporting a diagnosis of toxoplasmic lymphadenitis (15.3 per cent). In 80 of these patients (71 per cent), either Indirect Haemaglutination test (IHA), in 37 cases, or the Enzyme-Linked Immunosorbent Assay (ELISA) for detecting toxoplasmic IgG or IgM antibodies, in 43 cases, were performed. In 76 out of 80 patients (95 per cent), histological features correlated well with serological studies. The IHA test was positive in 30 patients with a titre of 1/64 or higher. The IgG-ELISA test was positive in 11 whereas the IgM-ELISA test was positive in 28 patients. These results provide further evidence of the distinctive nature of the histological changes in toxoplasmic lymphadenitis, which should enable the clinician to make a confident diagnosis of acute acquired toxoplasmosis.

Monocytoid B-cells occurring in Hodgkin's disease

In contrast with various forms of lymphadenitis, the presence of reactive monocytoid B-cells (MBCs) has only rarely been reported in Hodgkin's disease (HD). In order to analyse their occurrence in HD, we reviewed 120 cases before or after treatment. MBCs were identified morphologically and immunohistochemically in 8 cases (nodular paragranuloma, n = 2; nodular sclerosis, n = 2; and interfollicular mixed cellularity HD, n = 4). Acute toxoplasmic, cytomegalovirus, or Epstein-Barr virus (EBV) infections were excluded by serological tests and immunohistochemistry. MBCs were negative by immunostaining for EBV encoded latent membrane protein, while Sternberg-Reed and Hodgkin's cells expressed positivity in 50% of cases. MBCs were only identified in cases with partial or incomplete lymph node infiltration by HD together with an activated B-zone of residual non-infiltrated tissue. The relation of MBCs and HD infiltrates followed three distinct patterns: large HD infiltrates without any connection to MBC foci; small areas containing various numbers of Sternberg-Reed and Hodgkin's cells at the border between MBC foci and surrounding lymphoid tissue; and HD infiltrates within at least some MBC clusters. The data obtained suggest that MBCs occurring in HD represent a transient phenomenon associated with a B-zone activation irrespective of treatment and that they are usually not histogenetically related to HD.

The cytological spectrum of the monocytoid B-cell reaction: recognition of its large cell type

To analyse the cytological features of benign monocytoid B-cells, we investigated, histologically and immunohistochemically, 78 reactive lymphadenopathies expressing monocytoid B-cell reactions. Within a broad cytological spectrum of reactive monocytoid B-cells, two cytological types can be recognized: 1 the common type composed of medium-sized cells with irregular or bean-shaped nuclei and inconspicuous nucleoli, and 2 the large cell type composed of cells considered to represent large transformed monocytoid B-cells, with less pleomorphic round nuclei with vesicular chromatin and moderately basophilic, prominent nucleoli. In between these variants transitional forms showing evolution to large transformed monocytoid B-cells occurred. While monocytoid B-cell reactions in 70.5% of all cases were composed predominantly of the common type of monocytoid B-cells, in 29.5% of cases the large transformed cells prevailed. The two distinctive cytological types of reactive monocytoid B-cells seem to have their neoplastic counterparts in monocytoid B-cell lymphoma, including its large cell variant.

Monocytoid B-cell lymphomas: an assessment of diagnostic criteria and a perspective on histogenesis

To determine which morphologic criteria are most useful in distinguishing reactive from malignant monocytoid B cells (MBCs), we compared 16 monoclonal cases (11 nodal, five extranodal) of monocytoid B-cell lymphoma (MBCL) with 12 cases of various reactive diseases in which MBCs were polyclonal. The results of our study showed that in MBCL the MBC component was the predominant architectural finding and that there was confluence of MBCs in all but one case. In contrast, the MBC component did not predominate in the reactive group (P less than .000001) and focal confluence was seen in only one case. A cytologic comparison showed that in MBCL areas there were more large transformed (prominent nucleolated) MBCs (P = .003), a higher mitotic rate (P = .03), and more nuclear irregularities (P = .007) than were present in the reactive group. In addition, evolution to an aggressive histologic type was found in four cases of MBCL. Our results also revealed concomitant multiple, monoclonal, morphologically distinct populations in other compartments (follicular center cells in seven, mantle cells in five, small lymphocytes in five, and plasma cells in 11). These unique findings can be reconciled by postulating (1) that the simultaneous presence of these diverse cytologic types represents morphologic expressions of a B cell whose population is in different phases of its cell cycle and/or its evolution or (2) that the histogenesis of MBCL is possibly from a nodal pluripotent B-stem cell that can differentiate directly into these various cytologic types.

Infrequent detection of Toxoplasma gondii genome in toxoplasmic lymphadenitis: a polymerase chain reaction study

The diagnosis of toxoplasmic lymphadenitis is currently established by histologic evaluation with confirmation by serologic studies. We used a sensitive and specific polymerase chain reaction methodology for the identification of toxoplasmic genomes previously reported by others to investigate whether this technology could contribute to the diagnosis. We were able to reliably detect toxoplasmic genomes in paraffin-embedded tissues of toxoplasmic encephalitis and myocarditis, and serial dilution studies indicated a high degree of sensitivity. Nonetheless, we identified toxoplasmic genomes in frozen tissue from only one of nine cases of toxoplasmic lymphadenitis. In the one positive case, only one of three frozen samples from the lymph node biopsy was positive, indicating a focal infection within the lymph node. It is concluded that polymerase chain reaction studies, at their current level of sensitivity, are not of great use in contributing to the evaluation of cases of suspected toxoplasmic lymphadenitis, which continues to be best diagnosed by accurate histopathologic examination.

Monocytoid B cell lymphoma: clinical and prognostic features of 21 patients

Twenty one patients between 34 and 83 years of age with monocytoid B cell lymphoma (MBCL) of the lymph node were studied. The histological picture characteristically showed broad strands of medium sized cells with irregularly shaped nuclei and a fairly broad rim of slightly basophilic cytoplasm. One case developed into a centroblastic polymorphic lymphoma. Bone marrow infiltration was documented in three cases and leukaemic conversion in one case of MBCL. Seven patients had enlarged spleens. Eight patients were in stage I, five in stage II/IIE, two in stage IIIs and six in stage IV at the time of diagnosis. Of 18 patients subsequently followed up, eight were in complete remission, two in partial remission, and three were undergoing treatment at completion of the study; five patients had died. Relapse occurred in nine patients and was a common feature of MBCL. The prognosis of MBCL was comparable with that of other low grade malignant lymphomas. Fourteen patients presented with primary nodal lymphoma. In seven patients with nodal MBCL, however, a concomitant low grade B cell lymphoma of the mucosa-associated lymphoid tissue (MALT) was also found in the stomach (n = 4), nasopharynx (n = 1), salivary glands (n = 1) and thyroid gland (n = 1). Two of these cases developed into high grade lymphoma. These extra-nodal manifestations were found simultaneously with MBCL in five patients. In another two patients, however, these symptoms occurred in a later phase of the disease. It is emphasised that adequate staging procedures must be carried out in any case of nodal MBCL to exclude underlying low grade B cell lymphoma of the MALT.

Imprint cytology of non-Hodgkin's lymphomas based on a study of 212 immunologically characterized cases: correlation of touch imprints with tissue sections

The classification of non-Hodgkin's lymphomas (NHLs) has been traditionally based on analysis of histologic sections and has been supplemented more recently by immunologic marker studies. It was the purpose of the present study to illustrate, side-by-side, sections and Romanowsky-stained imprints from the same surgical specimen from practically all categories of immunophenotyped NHLs, including rare and atypical variants that were difficult to classify from the histologic sections alone. Our results indicate that imprint cytology may reveal nuclear and cytoplasmic details not discernible in even the best tissue sections and that it may be selectively helpful in contributing to the classification of NHLs. Our results also show that the relative value of imprint cytology in the classification of malignant lymphomas varies greatly among categories. Specifically, we have found that imprints assist in three ways: the recognition of plasmacytoid features in small cell lymphocytic lymphomas, the recognition of plasmacytoid immunoblastic lymphoma, and the differentiation between NHLs which may be difficult to distinguish histologically. These include (1) small lymphocytic lymphoma versus lymphocytic lymphoma of intermediate differentiation, (2) true histiocytic malignancies versus large cell malignant lymphomas with abundant cytoplasm and/or phagocytosis, (3) anaplastic myeloma versus plasmacytoid immunoblastic lymphoma, (4) large noncleaved versus plasmacytoid immunoblastic lymphoma, (5) lymphoblastic lymphoma versus diffuse small cleaved cell lymphoma, and (6) lymphoblastic lymphoma versus small noncleaved cell lymphoma. Lymph node imprints are easy to prepare and readily interpretable by those experienced in the study of abnormal blood and bone marrow films. Their value as an ancillary methodology aimed at optimal accuracy in the classification of NHLs should be recognized.

Two cases of acquired toxoplasmic lymphadenitis. Light and electron microscopic and immunohistochemical studies

We report two cases of acquired toxoplasmic lymphadenitis, one with toxoplasmic cysts and the organisms of Toxoplasma gondii and the other with the organisms only. These cysts and organisms were observed in paraffin-embedded sections, touch smears and ultrathin sections for electron microscopy. Touch smears were especially valuable for the quick and accurate diagnosis of toxoplasmic lymphadenitis. We also studied immature sinus histiocytosis (ISH) in these cases. The predominant cells of ISH were confirmed to be B lymphocytes immunohistochemically, the majority being positive for polyclonal surface IgM. ISH was observed in the perifollicular and paracortical areas surrounding post-capillary venules (PCV), whereas the sinuses were only partially involved.

Monocytoid B-cell lymphoma. A novel B-cell neoplasm

Monocytoid B lymphocytes (MBLs), originally described as part of the histologic picture of toxoplasmic lymphadenitis, have been recognized as a reactive component in a variety of lymph node disorders. The authors now report 3 cases of non-Hodgkin's lymphoma in which a multidisciplinary approach allowed them to confirm the existence of a malignant lymphoma composed of the neoplastic counterpart of the MBLs found in nonneoplastic disorders. In all 3 cases, the lymphoma was composed of a relatively monomorphous infiltrate of atypical MBLs that had rather uniform-appearing nuclei and had well-defined, moderately abundant pale cytoplasm. The pattern of lymph node involvement in all 3 cases was predominantly sinusoidal and interfollicular. The neoplastic lymphoid cells were strongly positive for B-cell-restricted antigens; the light- and heavy-chain phenotypes were kappa-IgM (2 cases) and kappa-IgG (1 case). In all 3 cases, rearrangement of heavy- and/or light-chain genes was clearly identified by Southern blot hybridization. The name "monocytoid B-cell lymphoma" is proposed for this newly described malignant B-cell neoplasm.

Lymph-node infarction and malignant lymphoma: a multicentre survey of European, English and American cases

A multicentre study of 51 cases of lymph-node infarction seen in the 30-year period 1956 to 1985 was conducted in order to assess both the short- and long-term prognostic implications of the condition. In 14 cases malignant lymphoma was found synchronously with the infarct. Of the remaining 37 patients with apparently 'benign' lymph-node infarction only six showed manifestations of malignant lymphoma in the follow-up time studied (mean = 48 months; range 1-156 months). These subsequent malignant lymphomas all occurred within 2 years of the lymph-node infarction. A postal enquiry and collation of other cases in the medical literature indicates that a minority (26 of 81) have developed malignant lymphoma, and that these lymphomas, too, have all appeared within 2 years. Thorough examination of both the infarcted lymph nodes and others resected at the same time is mandatory in order to exclude concomitant or underlying malignant lymphoma. Two years after lymph-node infarction the risk of malignant lymphoma is negligible.

Monocytoid B lymphocytes: their relation to the patterns of the acquired immunodeficiency syndrome (AIDS) and AIDS-related lymphadenopathy

It was shown recently that monocytoid cells express B-cell-restricted antigens and polyclonal surface immunoglobulins, and the term monocytoid B lymphocytes (MBL) has thus been offered as a more appropriate designation. Although most commonly seen in toxoplasmic lymphadenitis, MBL have been observed in a variety of reactive and neoplastic conditions involving lymph nodes. In the present study MBL were found in 17 of 22 lymph nodes from 20 patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related lymphadenopathy. In all 17 samples, the MBL were found in lymph nodes with florid reactive follicular hyperplasia, and they were geographically close to the hyperplastic lymphoid follicles. However, MBL were not detected in lymph nodes showing involuted follicles or lymphocyte depletion. The disappearance of MBL apparently parallels the progressive involution of secondary follicles. Leu-3+/Leu-2+ (T-helper/T-suppressor) ratios were studied in 14 lymph node cell suspension samples and ten peripheral blood samples. The lymph node Leu-3+/Leu-2+ ratios were significantly lower in AIDS-related lymphadenopathy than in non-AIDS-related reactive follicular hyperplasia (P less than 0.001); the peripheral blood ratios were decreased in nine of the ten cases. The diminished T-helper status in patients with AIDS and AIDS-related lymphadenopathy may be relevant to the immunopathogenesis of follicular involution and, indirectly, to the disappearance of MBL.

Immature sinus histiocytosis. Light- and electron-microscopic features, immunologic phenotype, and relationship with marginal zone lymphocytes

The light-microscopic, ultrastructural, and immunohistochemical features of immature sinus histiocytosis were studied in 10 lymph nodes with the histologic picture of toxoplasmic lymphadenitis and compared with the features of lymphoid cells present in the marginal zone of the splenic white pulp. Areas of immature sinus histiocytosis consisted largely of medium-sized lymphoid cells with markedly irregular nuclei and abundant pale cytoplasm. Using a panel of monoclonal antibodies, the predominating lymphoid cells were found to carry the B-cell phenotype B1+Ba1-sIgM+sIgD-OKIa1+. Admixed were variable numbers of larger, blastic lymphoid cells, small lymphocytes, histiocytic elements, and polymorphonuclear granulocytes. The marginal zone of the splenic white pulp was composed of a similar mixture of cells, and marginal-zone lymphocytes demonstrated an analogous immunohistochemical phenotype. Our results indicate that immature sinus histiocytes are B-lymphoid cells that are closely related to marginal zone lymphocytes. As such, immature sinus histiocytes may have a role similar to that of marginal-zone lymphocytes, which have been claimed to transport antigens or immune complexes toward the follicular center or to serve as precursors of plasma cells. We suggest that immature sinus histiocytosis represents an abnormal expansion of the marginal zone, normally present at the sinusoidal pole of lymphoid follicles. The reason for this marginal-zone hyperplasia, recognized as immature sinus histiocytosis in a variety of reactive lymph node conditions, may be a maturation arrest in the normal development of immature sinus histiocytes into small, sIgM+ sIgD+ lymphocytes.

The antigenic structure of Toxoplasma gondii: a review

Even though T. gondii is ubiquitous in the animal kingdom, definitive information on its antigenic structure has only become available over the last few years, largely as a result of recent advances in immunology and biochemistry. New knowledge in this area will enable the immune response to the parasite to be studied in greater detail and may lead to the development of newer, more meaningful diagnostic tests for toxoplasmosis, and possibly a vaccine against it. This paper reviews knowledge on the antigenic structure of this extremely widespread and important protozoan parasite.

Pathology of equine granulomatous enteritis

A morphological study on equine granulomatous enteritis (EGE) in 13 horses is presented. All horses were young (1 to 5 years old) standardbreds. Based on gross pathology, cases were classified into those with diffuse (11 cases) and those with localized (2 cases) small bowel lesions. The granulomatous reaction in the gut was marked by diffuse and patchy infiltrates and distinct granulomas, composed of epithelioid cells, macrophages and lymphoid cells, and was devoid of necrosis. Salient accompanying features of the small bowel included lymphoid hyperplasia, peri-lymphatic and transmural inflammation, lymphangiectasia, villous atrophy, mucosal ulcerations and crypt abscesses. Granulomatous changes were often demonstrated in alimentary tract tissues beyond the small bowel and its lymph nodes and were in some cases shown to occur multi-systemically. The morphology and epidemiological features of the condition suggest a specific aetiology. The histology indicated that an immune reaction was operative and that inflammation of the lamina propria was an early event in the pathogenesis of the gut lesion. No conclusive evidence of a specific infectious cause was found. It is suggested that the disease might be associated with intrinsic disturbances of inflammatory defence mechanisms.

Characterization of immature sinus histiocytes (monocytoid cells) in reactive lymph nodes by use of monoclonal antibodies

The distinctive mononuclear cells that appear in the cortical sinuses of lymph nodes in toxoplasma lymphadenitis and other conditions have been termed "immature sinus histiocytes," although these cells have neither enzyme histochemical nor ultrastructural features of histiocytes. The authors stained these cells in frozen sections of six reactive lymph nodes, using the immunoperoxidase technique, with monoclonal antibodies to T cell, B cell, and monocyte antigens and with heteroantisera to immunoglobulin and lysozyme. The immature sinus histiocytes stained with a monoclonal antibody to B cells (anti-B1) and had immunoglobulin of the IgG class. They did not react with monoclonal antibodies to T cells or monocytes or with antilysozyme. In contrast, medullary sinus histiocytes in three additional lymph nodes were B1-negative and reacted with anti-T4, anti-M1, and anti-lysozyme. These results indicate that immature sinus histiocytes are IgG-bearing B lymphocytes rather than histiocytes. Their role in the immune response remains enigmatic.

Toxoplasma cyst with toxoplasmic lymphadenitis

A toxoplasma cyst and the distinctive histopathologic changes of toxoplasmic lymphadenitis in a non-immunosuppressed patient with acute acquired toxoplasmosis are described. This is the third reported case in which the cyst form of toxoplasma has been observed in nodal tissue, and the first to be confirmed by electron microscopy.

Sinus histiocytosis with massive lymphadenopathy in a Nigerian child

Sinus histiocytosis with massive lymphadenopathy is a rare, benign lympho-proliferative disorder of unknown aetiology that chiefly affects the cervical lymphnodes of children. Various extranodal manifestations are recognized, especially in the head and neck. A case is described in a Nigerian child that illustrates problems of differential diagnosis.

Polymyositis and toxoplasmosis

Extensive severe polymyositis in a patient with toxoplasmosis was presented. Toxoplasmosis was serologically substantiated by a serial two tube rise in a toxoplasma-antibody titer by a hemagglutination test. When appeared to be toxoplasma gondii was detected in areas of myositis. Toxoplasma gondii was found in a single small area of hepatic necrosis, but no other organ or tissue was involved. Thus, the present case was peculiar in respect that skeletal muscles were the major target of toxoplasmosis. A causal relationship between toxoplasmosis and polymyositis was discussed and the literatures were reviewed. Serological investigation and histopathological search for toxoplasma gondii should be done in every case of polymyositis not only for the appropriate therapy but also for the further elucidation of the relationship between toxoplasmosis and polymyositis.

Histological differential diagnosis between lymph node toxoplasmosis and other benign lymph node hyperplasias

The material from 667 lymph nodes, originally suspected of toxoplasmosis, was histologically re-examined, to evaluate criteria for diagnosis and differential diagnosis. The results showed that at least 80% of benign lymph node enlargements containing small groups of epithelioid cells were associated with high titres of Toxoplasma antibodies. Furthermore, 85--95% of the lymph nodes in association with high Toxoplasma antibodies showed the typical histological appearances of toxoplasmosis. The histological diagnosis of toxoplasmosis is thus both fairly specific and sensitive. Other lymph node lesions with small groups of epithelioid cells must be considered in the differential diagnosis. Sarcoidosis and tuberculosis usually have a predominance of distinct large epithelioid cell granulomata. Lymph nodes with sinus histiocytosis showing the formation of small groups of epithelioid cells, do not demonstrate prominent hyperplasia and include sparse germinal centres and were not associated with toxoplasmosis. Lymph nodes with disturbed general structure and small groups of epithelioid cells must be carefully assessed because of the significant possibility of malignancy.

Acquired toxoplasma lymphadenitis

Toxoplasmosis is a common parasitic infection that is widely distributed throughout the world, including the United States. Its occurrence in the oral cavity, however, is uncommon. This report concerns a case of toxoplasmosis that manifested as an intraoral lymphadenitis in a 14-year-old white girl. The etiology, clinical, microscopic, and laboratory findings, and treatment are reviewed. The importance of recognizing lymphadenopathy as a clinical sign of this disorder is discussed.

Classification of lymphomas

Malignant lymphomas are neoplasms of cells of the lymphoreticular or immune system. Classification of these neoplasms has long been controversial and confusing. In recent years, considerable progress has been made in establishing useful and prognostically significant classifications of lymphomas. Currently, lymphomas may be divided into two main groups: Hodgkin's disease and non-Hodgkin's lymphomas. The Rye classification of Hodgkin's disease is now widely accepted and used throughout most of the world. In contrast, considerable conflict exists about the schemes of non-Hodgkin's lymphomas. The traditional classifications of non-Hodgkin's lymphomas currently used by most pathologists are based purely on morphologic grounds, and, despite the fact that they may be conceptually incorrect, they have often been shown to be useful for clinicopathologic studies. New or modern but yet untested schemes based not only on morphologic criteria, but also on recent immunologic techniques, have been proposed. This work will review the classifications of Hodgkin's disease and the non-Hodgkin's lymphomas, emphasizing the currently used schemes, describe the major modern classifications of lymphomas, and discuss and illustrate the subclasses of lymphomas and the differential diagnoses of the various types of lymphomas from nonlymphomatous proliferations which may mimic them.

Experimental toxoplasmic lymphadenopathy in rabbits

The pathogenesis of toxoplasmic lymphadenopathy was studied in rabbits. Sixteen were infected with a high virulence strain of Toxoplasma gondii and 32 with one of low virulence. The former group were killed and examined at intervals up to 9 days and the latter up to 129 days. The high virulence strain quickly caused paracortical hyperplasia but only moderate follicular reaction. Later, lymphoid depletion occurred. The low virulence strain caused follicular reaction so that at 16 days germinal centres had developed with evidence of cellular phagocytosis. Histiocytes were present and plasma cells were found in the medullary cords. These appearances were seen up to 51 days. At 86 days the follicular reaction was no longer present but had returned at 129 days. These results were supplemented by serological, parasitological, immunofluorescence and electron microscopic data.

The histological changes seen in the low virulence infections up to 51 days are unlike those caused by the high virulence strain but closely parallel those found in acquired infections in man, which are usually caused by strains of the low virulence type. These findings may help to elucidate the nature of the complex immune responses and the pathogenesis of toxoplasma infections.