T-zone lymphoma with predominance of 'plasmacytoid T-cells' associated with myelomonocytic leukaemia--a distinct clinicopathological entity

Unicentric Castleman Disease: Illustration of Its Morphologic Spectrum and Review of the Differential Diagnosis

CONTEXT.—

Unicentric Castleman disease (UCD) is a dynamic entity with a wide spectrum of morphologic findings. UCD can be further subdivided into hyaline-vascular and mixed/plasmacytic variants. Hyaline-vascular UCD has both follicular and interfollicular (stromal) changes, and occasionally these lesions show a skewed representation of either the follicular or stromal compartments. Plasmacytosis is usually minimal in the hyaline-vascular variant. The mixed/plasmacytic variant of UCD is composed of sheets of plasma cells often associated with a variable number of follicles with regressive changes.

OBJECTIVE.—

To illustrate the differential diagnosis of UCD, as it is quite broad and includes lymphomas, plasma cell neoplasms, stromal neoplasms such as follicular dendritic cell sarcoma and vascular neoplasms, immunoglobulin G4-related disease, infections, and other rare lesions. An additional objective is to enhance awareness of the morphologic features of UCD in excisional and in small core-needle biopsy specimens, the latter of which may inadvertently target follicle- or stroma-rich areas, causing diagnostic challenges.

DATA SOURCES.—

In this review, we provide readers a concise illustration of the morphologic spectrum of UCD that we have encountered in our practice and a brief discussion of entities in the differential diagnosis.

CONCLUSIONS.—

UCD exhibits a broad spectrum of morphologic changes, and awareness of these morphologic variations is key to avoid misdiagnosis.

T Lymphoblastic Lymphoma Hiding in Mature Plasmacytoid Dendritic Cell Proliferation: A Case Report and Literature Review

To the best of the author's knowledge, studies of mature plasmacytoid dendritic cell proliferation associated with T lymphoblastic lymphoma were extremely rare in the literature. Here, we report a patient who underwent both mature plasmacytoid dendritic cell proliferation and T lymphoblastic lymphoma. With the findings of lymph node biopsy taken from the right cervical and inguinal regions, we identified eye-catching mature plasmacytoid dendritic cells that were considered to be responsible for this lesion at the beginning, until the immunostaining of Ki67 and TDT showed a small group of positive cells hiding in these plasmacytoid dendritic cells. A bone marrow biopsy was also performed on this patient. Microscopically, the hematopoietic tissue was almost completely replaced by lymphoblastoid cells with condensed chromatin, inconspicuous nucleoli and scanty cytoplasm, which were basically the same as those seen in the lymph nodes in morphology. However, there was no sign of plasmacytoid dendritic cells or Langerhans cells in the bone marrow biopsy. With the help of bone marrow biopsy, our final diagnosis of the lymph node was T lymphoblastic lymphoma coexisting with mature plasmacytoid dendritic cell proliferation. Although accumulations of plasmacytoid dendritic cells may occur in some infections or reactive lymphadenopathy, the presence of extensive nodules or infiltration of plasmacytoid dendritic cells strongly reminds the pathologist to carefully evaluate the bone marrow or peripheral blood status of the patient to exclude a hidden myeloid or other neoplasm.

Chronic Myelomonocytic Leukemia Coexisting with B-cell Chronic Lymphocytic Leukemia

Coexistence of B-cell chronic lymphocytic leukemia (B-CLL) and chronic myelomonocytic leukemia (CMML) is an unusal event, and to our knowledge, only four such cases have been reported in the literature. We report a 68-year-old white woman in whom these two diseases were diagnosed concomitantly. The diagnosis was made on the basis of peripheral blood count, morphology and immunophenotyping, and bone marrow cytology and histology. Interphase FISH analysis detected a 13q14.3 deletion in lymphocytes nuclei and no such abnormality in monocytes nuclei. The PCR analysis of IgH gene rearrangement in the bone marrow, as well as the peripheral blood lymphocytes, showed two different monoclonal IgH configurations as the result of biallelic clonal rearrangement of IgH genes suggesting an origin of lymphocytes from B-cell progenitors. The patient was originally treated with prednisone 1 mg/kg/day because of progressive significant thrombocytopenia, without improvement. Subsequently, she received one course of cladribine (2-CdA). Significant reduction of lymphocytes in the peripheral blood was observed. However, rapid increase of monocytes was seen shortly after the 2-CdA treatment. Subsequently, she received hydroxyurea (1.5 g/day) without hematological improvement. The patient died in January 2003, three months after diagnosis because of progression of both leukemias and associated pneumonia. Possible etiopathogenic relationship between both disorders is discussed.

CD4+/CD56+ hematodermic neoplasm: presentation of 2 cases and review of the concept of an uncommon tumor originated in plasmacytoid dendritic cells expressing CD123 (IL-3 receptor alpha)

CD4/CD56 hematodermic neoplasm is a rare neoplasm presenting with cutaneous nodules, lymphadenopathy, bone marrow infiltration, and an aggressive clinical course. Recently, the plasmacytoid dendritic cell origin of this neoplasm has been demonstrated. Plasmacytoid dendritic cell is a hematopoietic-derived cell implicated in the regulation of innate and adaptive cell immunity and in the production of certain regulatory cytokines. Recently it has been demonstrated that these cells express cell surface markers such as IL-3 receptor alpha (CD123). In the present report, we describe the clinical, histologic, and immunohistochemical characteristics of 2 cases of CD4/CD56 hematodermic neoplasm. Both patients were male and the age at the time of diagnosis was 36 and 75 years, respectively. Clinical findings were limited to the skin and consisted of multiple cutaneous nodules located in the thorax and extremities, some of them ulcerated. Histologically, the tumors were characterized by a nonepidermotropic, dermal and subdermal infiltration of homogeneous medium-sized cells resembling lymphoblasts or myeloblasts. Immunohistochemical characterization of the tumors showed expression of CD4, CD56, CD43, and CD123, whereas CD8, CD20, and MPO were negative. Immunoreactivity for CD3, which has been described in rare occasions, was found only in one of the cases. This characteristic profile in addition to the expression of CD123, which was detected in both cases, can be used as valuable tools in the diagnosis of this rare neoplasm.

Novel markers of normal and neoplastic human plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) are involved in innate immunity (eg, by secreting interferons) and also give rise to CD4+CD56+ hematodermic neoplasms. We report extensive characterization of human pDCs in routine tissue samples, documenting the expression of 19 immunohistologic markers, including signaling molecules (eg, BLNK), transcription factors (eg, ICSBP/IRF8 and PU.1), and Toll-like receptors (TLR7, TLR9). Many of these molecules are expressed in other cell types (principally B cells), but the adaptor protein CD2AP was essentially restricted to pDCs, and is therefore a novel immunohistologic marker for use in tissue biopsies. We found little evidence for activation-associated morphologic or phenotypic changes in conditions where pDCs are greatly increased (eg, Kikuchi disease). Most of the molecules were retained in the majority of pDC neoplasms, and 3 (BCL11A, CD2AP, and ICSBP/IRF8) were also commonly negative in leukemia cutis (acute myeloid leukemia in the skin), a tumor that may mimic pDC neoplasia. In summary, we have documented a range of molecules (notably those associated with B cells) expressed by pDCs in tissues and peripheral blood (where pDCs were detectable in cytospins at a frequency of <1% of mononuclear cells) and also defined potential new markers (in particular CD2AP) for the diagnosis of pDC tumors.

Les hématodermies CD4/CD56

Hematodermic CD4/CD56 neoplasm is a recently described entity. This name has been initially proposed by the French Study Group on Cutaneous Lymphomas which established the primary anatomoclinical and pathogenic and cytogenic bases of the disease in 1999. This descriptive and provisional name allowed conceptualizing the entity by its main clinical and phenotypical characteristics. The first case in the literature goes back to 1994. Since that time, several other cases have been published. The expression of CD56 led most of the authors to propose an NK-cell lineage origin. In the last WHO classification of lymphomas, the entity was indexed under the name of "blastic NK-cell lymphoma". However, the authors underlined that there were currently no clues to the etiology of blastic NK-cell lymphoma and that the precise lineage of this disease was still unresolved. At the clinical level the main characteristics of the disease are the skin tropism and the occurrence of a leukemic phase at any time during the course of the disease. The median age is 59 but pediatric cases do exist. At the morphological level skin biopsy shows a monomorphous cell proliferation simulating a pleomorphic T cell cutaneous lymphoma. The diagnosis is based on phenotypic criteria which require frozen tissue. Currently, the main characteristics are the expression of CD4 and CD56 antigens while the main defined lineage specific markers are negative (B-cell, T-cell, NK-cell and myeloid-cell lineages). The origin of the tumor cells still remains uncertain but the plasmacytoid dendritic cell is presently a very serious candidate. The tumor cells share a great phenotypical homology and particularly the expression of the CD123 antigen. Functional homologies have also been demonstrated with tumor cells in vitro. Outcome of CD4/CD56 hematodermic neoplasms is very bad. The median time of survival is 14 months irrespective of the treatment given. Conventional chemotherapies used for the treatment of aggressive lymphomas or acute myeloid leukemias are quickly inefficient.

Nodal and Extranodal Tumor-forming Accumulation of Plasmacytoid Monocytes/Interferon-producing Cells Associated With Myeloid Disorders

Nodal tumor-forming accumulations of plasmacytoid monocytes/interferon-producing cells (PMs/IPCs) have been described in patients with myeloproliferative disorders. Here we report a series of 9 additional cases of such association. The patients were predominantly adult (median, 62 years), males (male/female ratio, 7:2), who presented with chronic myelomonocytic leukemia (4 cases), acute myeloid leukemia (1), acute monocytic leukemia (2), unclassifiable chronic myeloproliferative (1), or myeloproliferative/myelodysplastic disease (1). The prognosis was poor (median survival, 24 months) and related to progression of the underlying myeloid neoplasm. We found that in addition to lymph nodes, PMs/IPCs accumulated to bone marrow (8 cases) and skin (4 cases). Immunohistochemical markers typically expressed by PMs/IPCs (CD68, CLA/HECA452, CD123) were found in all cases and shown useful to identify cells with variations from classic morphology. In addition, PMs/IPCs expressed the interferon-alpha (IFN-alpha) inducible protein MxA, the B-cell oncogene TCL1, and granzyme B. The biologic and clinical significance of the association between PMs/IPCs and myeloid disorders remains not clarified. Using fluorescence in situ hybridization analysis in a case known to harbor monosomy 7 in the myeloid leukemia, we demonstrated that PMs/IPCs share the same chromosomal abnormality, thus indicating that they are clonal, neoplastic in nature, and closely related to the associated myeloid tumor. Recently, a novel CD56+ hematologic neoplasm has been reported and retained to stem from PMs/IPCs. The majority of PMs/IPCs in the present series failed to express CD56, thus indicating that variants of PMs/IPCs neoplasms exist, which might represent parts of a spectrum.

Involvement of plasmacytoid dendritic cells in human diseases

In vitro studies have reported that plasmacytoid dendritic cells (PDCs) exert multiple functions, including production of interferon (IFN)-alpha as effector cells and regulation of T-cell responses as mature DCs. Here we review recent data obtained in situ showing that PDCs accumulate in lesions of type I IFN-related disorders (virus infections and lupus erythematosus), Th2 cell-dominated allergic reactions, and ovarian carcinoma. These results demonstrate that PDCs do migrate to peripheral tissues during inflammation, which lends further support to the view that PDCs most likely are important players in innate and adaptive immunity in vivo. Future research should aim at defining the exact pathogenic or defense roles of PDCs in such disorders and determine whether these cells are potential targets for therapeutic intervention in microbial infections, allergy, autoimmunity, or cancer.

Experimentally induced recruitment of plasmacytoid (CD123high) dendritic cells in human nasal allergy

Recent evidence suggests that the previously enigmatic cell type designated plasmacytoid monocytes can function as dendritic cells and contribute substantially to both innate and adaptive immunity. This cell type has previously been described only in bone marrow, blood, and organized lymphoid tissue, but not at effector sites with direct Ag exposure such as the mucosae. Plasmacytoid dendritic cells (P-DCs) matured in vitro can induce T cells to produce allergy-promoting Th2 cytokines; therefore, their possible occurrence in nasal mucosa during experimentally elicited allergic rhinitis was examined. Patients with silent nasal allergy were challenged topically with relevant allergen daily for 7 days. Biopsy specimens as well as blood samples were obtained before and during such provocation, and P-DCs were identified by their high expression of CD123 (IL-3R alpha-chain), together with CD45RA. Our results showed that P-DCs were present in low and variable numbers in normal nasal mucosa but increased dramatically during the allergic reaction. This accumulation concurred with the expression of the L-selectin ligand peripheral lymph node addressin on the mucosal vascular endothelium. The latter observation was particularly interesting in view of the high levels of L-selectin on circulating P-DC precursors and of previous reports suggesting that these cells can enter organized lymphoid tissue via high endothelial venules (which express peripheral lymph node addressin constitutively). Together, our findings suggested that P-DCs are involved in the triggering of airway allergy and that they are directed to allergic lesions by adhesion molecules that normally mediate leukocyte extravasation in organized lymphoid tissue.

Dendritic cell origins: puzzles and paradoxes

In the present review, a series of studies on the origins of dendritic cells of mice and humans are summarized. Several subsets of mature dendritic cells found in vivo are described and these may correspond to distinct lineages. There is evidence that some dendritic cells are myeloid-derived and that others are lymphoid-derived. The different ways of generating dendritic cells are examined and an attempt to reconcile the differences seen using mouse and human culture models is made. The particular case of Langerhans cells is discussed and an historical overview of the biology of the plasmacytoid T cells, which may represent a distinct 'lymphoid-related' dendritic cell lineage, is given. It is concluded that three or four different pathways lead to the development of different subtypes of dendritic cells.

The enigmatic plasmacytoid T cells develop into dendritic cells with interleukin (IL)-3 and CD40-ligand

A subset of CD4+CD11c-CD3- blood cells was recently shown to develop into dendritic cells when cultured with monocyte conditioned medium. Here, we demonstrate that CD4+ CD11c-CD3- cells, isolated from tonsils, correspond to the so-called plasmacytoid T cells, an obscure cell type that has long been observed by pathologists within secondary lymphoid tissues. They express CD45RA, but not markers specific for known lymphoid- or myeloid-derived cell types. They undergo rapid apoptosis in culture, unless rescued by IL-3. Further addition of CD40-ligand results in their differentiation into dendritic cells that express low levels of myeloid antigens CD13 and CD33.

Evidence for a lymphotropic nature of circulating plasmacytoid monocytes: findings from a case of CD56+ chronic myelomonocytic leukemia

Because the cells previously designated plasmacytoid T cells share major immunophenotypic features with cells of the mononuclear-phagocyte system, they have been re-named and are now known as plasmacytoid monocytes (PM). We describe a unique case of chronic myelomonocytic leukemia with circulating PM. The patient, a 48-year-old man, presented initially with refractory anemia. Four years later his general condition deteriorated, accompanied by an increase in leukocytes to 200,000/microliters blood. The bone marrow histology was interpreted as compatible with a diagnosis of chronic myelomonocytic leukemia. Two months before he died, the patient developed generalized lymphadenopathy clinically simulating malignant lymphoma. Histologic examination of an axillary lymph node revealed diffuse infiltration by PM. The PM in the lymph node and some circulating cells closely resembling PM expressed L-selectin, a finding that could be interpreted as a morphologic correlate of their marked lymphotropism. The detection of large numbers of CD56/CD33 double-positive circulating blast cells by FACS analysis strongly supported the diagnosis of a leukemia of myelogenous origin. The patient died of tumor cachexia. Autopsy revealed widespread leukemic infiltrates (always containing clusters of PM) in bone marrow, spleen, liver, lymph nodes, and mucosa-associated lymphoid tissue of the oropharynx. The final diagnosis was one of chronic myelomonocytic leukemia with marked lymphotropism and partial differentiation towards PM. We consider that the rare instances of a hematologic tumor with differentiation towards PM should be classified amongst the myelogenous leukemias.

t(8;13) (p11;q12) translocation in a myeloproliferative disorder associated with a T-cell non-Hodgkin lymphoma

An unusual cytogenetic translocation, t(8;13) (p11;q12), is described in a patient presenting with a CML-like myeloproliferative disorder associated with a high-grade T-cell lymphoma. Evidence is presented suggesting that the breakpoint region in the translocation involves a site implicated in both the T cell malignancy and the abnormal granulocyte proliferation.

Lectin-binding profile of plasmacytoid monocytes

The lectin-binding profile of plasmacytoid monocytes, also known as plasmacytoid T cells, was studied in 18 axillary lymph nodes draining invasive breast carcinomas. The plasmacytoid monocytes bound fluorescein-conjugated lectins from Canavalia ensiformis (Con A), Phaseolus vulgaris (PHA-L), Arachis hypogaea (PNA), Ricinus communis (RCA I and II), and Triticum vulgaris (WGA), but no reaction was found with those from Dolichos biflorus (DBA) and Ulex europaeus (UEA I). Fluorescence was bright and the reactivity was distributed in a granular pattern in the cytoplasm of plasmacytoid monocytes, a staining pattern similar to that of monocytes and macrophages. B and T lymphocytes usually exhibited weak staining with the same lectins, and this was limited to the cell membrane. Plasmacytoid monocytes were originally thought to be closely related to the T-cell system. The results of recent immunocytologic studies and the lectin-binding profile of plasmacytoid monocytes observed in this study, however, suggest that these cells are related to the mononuclear phagocytic system.

Plasmacytoid monocyte proliferation associated with myeloproliferative disorders

Plasmacytoid T-cell (PTC) lymphoma is a rare clinicopathologic entity characterized by generalized lymphadenopathy in association with a myeloproliferative disorder. Hepatosplenomegaly and weight loss frequently are present. Nodal T-zone expansion by mononuclear cells with ultrastructural and immunohistochemical features typical of PTC is diagnostic. All of the five previously reported cases of PTC lymphoma coincided with or heralded the onset of a clinically aggressive myeloid leukemia. This strong association and recent immunohistochemical findings in reactive or neoplastic PTC favored a monocyte/macrophage derivation of these cells, and it has been suggested that they be renamed plasmacytoid monocytes (PM). Two additional cases of PTC lymphoma were studied at the institutions of the authors, and the findings supported the concept that PTC belong to the monocytic lineage. The disease presentation was generalized lymphadenopathy with constitutional symptoms. One patient also had hepatosplenomegaly and bilateral renal enlargement concomitantly with myelofibrosis with myeloid metaplasia that progressed within months to acute myelogenous leukemia. Similar rapid evolution of acute monoblastic leukemia occurred in the other patient. Tumor cells within subtotally effaced lymph nodes had positive findings for CD45, CD4, CD7, and LN2 and negative findings for CD3, CD8, and beta F1. Occasional cells had positive findings for CD2. One case demonstrated CD5, HLA-DR, CD71, and CD43 (Leu-22)-positive cells. The myeloid/monocyte-associated antigens CD14 and CD68 were identified in both. The tumor cells lacked the B-cell markers LN1, CD20 (L26), CD19, and CD22 and did not rearrange immunoglobulin heavy chain genes and T-cell receptor beta, gamma, and delta chain genes. The term plasmacytoid T-zone lymphoma or PM proliferation is more appropriate for this rare disease. The close association of the PM proliferation with a myeloproliferative disorder indicates that the two entities are related.

Immuno- and enzymehistochemical characterization of 'plasmacytoid T-cells' in formalin-fixed paraffin-embedded tissue of reactive lymph nodes

In eight (10.4%) of 77 randomly selected cases of lymphadenitis, foci of 'plasmacytoid T-cells' (PTCs) were found. We characterized the PTCs in formalin-fixed paraffin-embedded tissue by immuno- and enzymehistochemical techniques. In each case the PTCs formed nodular and patchy infiltration patterns around the high endothelial venules in the paracortex of the lymph nodes. The PTCs in half of the cases were present near the intermediary peritrabecular sinuses. The PTCs were found to be positive for CD 45 (LCA), CD 45 R (4 KB 5) and CD 43 (MT 1), but not for CD 45 RO (UCHL 1), L 26 (CD 20), myeloperoxidase, naphthol AS-D chloroacetate esterase, Mac 387, alpha-1-antichymotrypsin or S 100 protein and anti-dendritic reticulum cell antibody. Some lysozyme+ PTCs were mingled in and around the foci in each case. In five cases the PTCs showed weaker positive reactions for CD 68 (EBM 11) and HLA-DR than for T-zone macrophages and sinus histiocytes. Related to the degree of desintegration of the nodular PTC-foci increasing numbers of T- and B-lymphocytes, T-zone macrophages and interdigitating reticulum cells with HLA-DR were detected in the foci. In two cases, where there was no HLA-DR expression by PTCs, small amounts of HLA-DR in secondary lymph follicles and a decrease of HLA-DR+ T-zone macrophages and interdigitating reticulum cells were observed. Our results suggest that there is a high degree of interaction between PTCs and other cellular components in the lymph node. The PTC may represent a special type of resident macrophage with secretory capacities.

Immunohistological diagnosis of "plasmacytoid T cell lymphoma" in paraffin wax sections

An immunohistological study of paraffin wax embedded tissue from three cases of plasmacytoid monocyte neoplasms, using a panel of antibodies which react with fixation resistant leucocyte markers, is reported. This neoplasm was found to have a distinctive antigenic profile, being negative for CD3 and elastase, but positive for CD43 and CD68. This immunological phenotype, coupled with its characteristic morphological features, should facilitate the recognition of this rare neoplasm in routinely processed tissue. Furthermore, the term "plasmacytoid monocyte sarcoma" is proposed to designate it because it is inappropriate to refer to it as a lymphoma. As all cases have been associated with a myeloproliferative disorder (usually an acute or chronic myeloid leukaemia), these tumours probably represent the accumulation in lymphoid tissue of neoplastic cells which have differentiated along the plasmacytoid monocyte pathway.

Sequential development of peripheral T-cell lymphoma in the course of chronic myelogenous leukemia

A patient is described with chronic myelogenous leukemia (CML) and an unusual karyotype 46XY,t(Y;12) (q11;p12), whose clinical course was complicated by T-cell lymphoma 5 years later. At that time bone marrow cells showed an additional karyotypic abnormality 46XY,t(Y;12) (q11;p12) del(7) (pter-p21), which remained unchanged until blastic transformation of the CML 8 months later. The bone marrow biopsy specimen, which revealed the blastic transformation of the CML, also showed evidence for localization of T-cell lymphoma. This case, added to two previously reported cases of the concurrence of CML and T-cell lymphoma, suggests a relationship between the two diseases, which is discussed.

Plasmacytoid monocytes in epithelioid cell granulomas: ultrastructural and immunoelectron microscopic study

Plasmacytoid monocytes, the so-called plasmacytoid T cells, were originally described in rare cases of lymphadenitis. Recent immunohistochemical studies have demonstrated their monocytic origin. Plasmacytoid monocytes have in common with epithelioid cells and multinucleated giant cells the expression of several antigens; they also occur in close topographic association with epithelioid and multinucleated giant cells in epithelioid cell granulomas. On the basis of these data it has been suggested that plasmacytoid monocytes may transform into epithelioid cells. The present ultrastructural and immunoelectron microscopic study of epithelioid cell granulomas provides further arguments in favor of this hypothesis. Moreover, the existence of a transitional cell type with characteristics of plasmacytoid monocytes and epithelioid cells is documented. Subplasmalemmal linear densities present on focal areas of the plasma membrane of the main cell components of granulomas are also discussed.

The plasmacytoid T cell or plasmacytoid monocyte--a sessile lymphoid cell with unique immunophenotype and unknown function, still awaiting lineage affiliation

Clusters of cells with a plasmacytoid appearance have been identified in T zones of human lymphoid tissue. These cells were shown to express the CD4 antigen in the absence of B-cell antigens. Thus, they were named "plasmacytoid T cells" (PTCs). Recent studies, however, have suggested a myelomonocytic origin of this cell type, which led to the designation "plasmacytoid monocytes." In order to obtain a comprehensive immunophenotype of this cell, we used frozen serial sections of lymph nodes, an indirect immunoperoxidase technique, and a broad panel of well-defined monoclonal antibodies (mAbs). On PTCs, the antigenic density was high for CD4 and CD26 antigens and low for CD2; they furthermore reacted with the mAb OKM5 recognizing an undefined antigen associated with the myelomonocytic lineage and expressed the monocyte-associated antigen CD68. PTCs expressed HLA-A, B, C, HLA-DR, and the HLA-D associated invariant chain (Ii) while HLA-DP antigens were expressed only in low amounts and HLA-DQ antigens were lacking entirely. PTCs further expressed the adhesion molecule CD11c. The absence of detectable transferrin receptor and the proliferation antigen defined by Ki-67 indicated that PTCs were nonproliferating. Other well-defined antigens confined to the T-, B-, and myelomonocyte lineages could not be detected in the target cell population. For us, antigenic equipment is still suggestive of a sessile, terminally differentiated T cell likely to exert a secretory function as yet unknown.

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.

Peripheral T-cell lymphoma

Since the discovery of human T-cell leukemia virus type 1 (HTLV-1) in patients with adult T-cell leukemia/lymphoma (ATLL), malignant neoplasms of mature (peripheral) T lymphocytes have attracted a great deal of attention. This type of neoplasm is more common in Japan than in Western countries, and may show distinct clinical pictures such as hypergammaglobulinemia, hypercalcemia, etc. T-cell lymphomas are more prone than B-cell lymphomas to become leukemic. Because of a marked intermingling of reactive cells (histiocytes, eosinophils, etc.), the histologic diagnosis of T-cell lymphoma is often difficult. Proliferation pattern and cellular size do not correlate with prognosis as in B-cell lymphoma. Since T-cell lymphomas often manifest with several distinct clinicopathologic settings, their categorization should be based on several parameters, such as the presence or absence of ATLL-associated antigen in serum, histology, phenotype of the neoplastic cell, and clinical features. Since a classification for T-cell lymphomas has not been established, a further multi-disciplinary approach is necessary for a better understanding of this interesting neoplasm.

Plasmacytoid T cells: a cell population normally present in the reactive lymph node. An immunohistochemical and electronmicroscopic study

Plasmacytoid T cells (PTCs) are medium-sized cells characterized by abundant rough endoplasmic reticulum. They occur in the thymic-dependent area in human lymph nodes. PTCs are hardly identified in routinely stained sections. We studied their occurrence in 100 reactive lymph nodes with the use of monoclonal antibodies MB2, MT1, LN1, LN2, reactive on paraffin-embedded tissue, and with electron microscopy in nine selected cases. PTCs strongly reactive with MT1 and LN2 were found in 87 of 100 lymph nodes. They were observed in clusters, loose aggregates, and as singular cells. An association between PTCs, postcapillary venules, small T lymphocytes, and interdigitating reticulum cells (IDRCs) was found. Our results indicate that PTCs are normally present in the human lymph node. Their immunophenotype suggests a relationship with a monocyte/macrophage lineage, but does not rule out a T cell origin. If the various distribution patterns represent the morphologic substrate of functional stages of PTCs it can be assumed that PTCs play a role in T cell-mediated immune response.

Histopathology and immunohistochemistry of peripheral T cell lymphomas: a proposal for their classification

Based on the results of histological and immunohistochemical observations of a large number of peripheral T cell lymphomas from China, England, Germany and Japan, histological and cytological morphology were correlated with immunophenotype, aetiological association with HTLV-1, and clinical behaviour to produce a working classification of the T cell lymphomas. This classification, based mainly on cytological criteria, divides the peripheral T cell lymphomas into tumours of low grade and high grade malignancy. Adult T cell lymphoma/leukaemia (ATLL) is caused by HTLV-1 and belongs chiefly to the high grade category. Some tumours are characterised by an admixture of other cells (epithelioid cells, follicular dendritic cells, etc) and structures (high endothelial venules, follicles), which may indicate the secretion of lymphokines by the tumour cells. Clear cells seem to be specific for T cell lymphomas and may occur in various types of peripheral T cell lymphoma.