EBM/11 reactivity in malignant histiocytosis

Histiocytic sarcomas

In this study a review of malignancies classified as histiocytic in the literature is given. The available data suggest that a distinction can be made between three main categories, i.e., follicular dendritic cell (FDC) sarcomas, Langerhans' cell/interdigiting reticulum cell (LC/IRC) sarcomas and histiocytic sarcomas (HS) which are unrelated to accessory cells. With the exception of FDC sarcomas these tumours are high-grade malignancies with an aggressive course and short survival times. The recognition of FDC sarcomas and LC/IRC sarcomas rests upon the identification of accessory cell related antigens (e.g., R4/23, CD1a, S-100) and/or the demonstration of desmosomes or Birbeck granules. The diagnosis of HS which are unrelated to accessory cells is more complex. These tumours are heterogenous with respect to morphology and phenotype and can only be recognized with the use of an extensive panel of antibodies supplemented when possible by analysis of T-cell receptor--or immunoglobulin genes.

KP1 (CD68)-positive large cell lymphomas: a histopathologic and immunophenotypic characterization of 12 cases

CD68/KP1 antigen expression in a series of 298 non-Hodgkin's lymphoma (NHL) cases, including 41 cases of CD30/Ki-1-positive anaplastic large cell (Ki-1+ ALC) lymphomas, was examined. Among the cases in this series, 12 large cell NHLs, including five centroblastic (G group according to the Working Formulation) NHLs, three immunoblastic (H group) NHLs, and four Ki-1+ ALC lymphomas, were found to express KP1. By extensive immunophenotypic analysis and in situ hybridization, KP1-positive large cell lymphomas of the G and H groups were assigned a B-cell phenotype. The pattern of KP1 staining usually consisted of localized small to medium-sized cytoplasmic dots; only two cases showed diffuse fine granular reactivity. In two of the four Ki-1+ ALC lymphomas tumor cells failed to express a B- or T-cell phenotype and stained positively for lysozyme, whereas in the other two cases they showed a hybrid T/histiocytic, phenotypic profile. KP1 staining of Ki-1+ ALC lymphoma cells was usually intense and showed a diffuse granular cytoplasmic pattern; tumor cells also expressed the CD13 antigen and showed strong reactivity with the anti-CD68 EBM11 antibody. Our results suggest that certain subsets of large "blastic" B-cell lymphomas may simultaneously express the CD68/KP1 histiocyte-specific marker and other myeloid-associated antigens, indicating the necessity of using a multiparameter approach in the determination of cell lineage. Moreover, this study, which demonstrates that the expression of CD68/KP1 and CD30 antigens is not mutually exclusive, supports the view that a fraction of cases diagnosed as Ki-1+ ALC lymphomas (at least those with KP1 expression along with the lack of B- or T-antigen expression) represent true histiocytic lymphomas despite the Ki-1+ phenotype.

Growth factor (M-CSF) and antigenic properties of macrophages in meningioma

In meningiomas, transformed meningeal cells can share morphological aspects (in hemangiopericytic meningioma) and antigenic properties (i.e.: HLA-DR antigens expression) with elements of the monocyte/macrophage lineage. In this report, we describe a case of a highly vascular meningioma where numerous tumor cells, studied with immunohistochemical methods, present phenotypic properties of macrophages. Moreover, the cerebrospinal fluid (CF) analysis disclosed, using a biological assay, a high level of a growth factor for monocytic elements, the Macrophages Colony Stimulating Factor (M-CSF). Our findings may confirm that transitional aspects between different mesenchymal cells could be present in meningiomas.

Histopathologic, immunophenotypic, and genotypic analysis of Ki-1 anaplastic large cell lymphomas that express histiocyte-associated antigens

CD30/Ki-1 antigen expression in 243 cases of malignant lymphomas was examined using Ber-H2 monoclonal antibody. Among them 20 cases were categorized as Ki-1 anaplastic large cell lymphoma. In two of these cases histiocyte-associated markers were also expressed. In these cases histopathologic and extensive in situ immunophenotypic analyses were used with genotypic studies in the determination of cell lineage. A sinusoid histologic pattern of involvement with partial lymph node infiltration by pleomorphic neoplastic cells was noticed in the nodes from both patients. Solid areas of node replacement resembling metastatic carcinoma were seen in Patient 1. Immunohistologically, tumor cells of both cases were positive for CD30, CD25, CD71, LN3 (HLA-DR), EMA, CD45, CD74, vimentin, alpha-1-antichymotrypsin, and CD68. Patient 1 was also CD45RO+, CD43+, whereas Patient 2 was positive for alpha-1-antitrypsin and CD4 tumor cells. Genotypic studies revealed that TCR beta and TCR gamma chain genes were clonally rearranged in Patient 1, whereas no rearrangements were detected in Patient 2. This study supports the view that some Ki-1 anaplastic large cell lymphomas may express multiple histiocyte-associated antigens and confirms that this group of neoplasms have immunophenotypic heterogeneity. The results of genotypic analyses used with immunophenotyping does not exclude that the tumor cells in these cases may be of true histiocytic origin despite the Ki-1-positive phenotype.

Malignant lymphomas of true histiocytic origin. A clinical, histological, immunophenotypic and genotypic study

The clinical, histological, immunophenotypic and genotypic properties of four cases of lymphoma of true histiocytic origin are described. The cases were identified by typing 925 non-Hodgkin's lymphomas by immunophenotypic and/or genotypic techniques, and they all presented with skin lesions. The histological and immunophenotypic examination showed dense, diffuse infiltrates of markedly pleomorphic mononuclear cells that were positive for macrophage-associated markers, and negative for B-cell, T-cell and myeloid cell-associated antigens. Staining for Ki-1 and epithelial membrane antigen was also negative. Gene rearrangements studies were performed in three cases, and all of these showed germline configuration of both T-cell receptor and immunoglobulin genes. In all cases, the clinical course was aggressive with rapid and widespread dissemination to internal organs, poor response to conventional chemotherapy, and short survival times (0.5 to 14 months). This suggests that although true histiocytic tumours are very rare, their recognition may be important for clinical and/or prognostic reasons.

Diagnosis of myelomonocytic and macrophage neoplasms in routinely processed tissue biopsies with monoclonal antibody KP1

A new monoclonal antibody, KP1, against the CD68 antigen, which labels macrophages and other members of the mononuclear phagocyte lineage in routinely processed tissue sections, has been used to stain a range of lymphoid, histiocytic, and myelomonocytic proliferations. All 20 neoplasms of myeloid, myelomonocytic, and presumed macrophage derivation reacted with antibody KP1. None of the 22 cases of T cell neoplasia had positive reactions. Although 14 of 41 B lineage lymphomas and leukaemias were stained by antibody KP1, staining was usually confined to small dots of reactivity, in contrast to the strong and extensive cytoplasmic staining seen in the neoplasms of myeloid and macrophage/monocyte origin. Furthermore, positive B cell neoplasms were almost all small cell proliferations, which are unlikely to be confused with myelomonocytic malignancies. It was concluded that antibody KP1 is a valuable addition to a panel of monoclonal antibodies for phenotyping lymphomas, particularly in routinely fixed tissues. It should assist the pathologist in the recognition of extramedullary presentation of leukaemia, aid in the diagnosis of suspected cases of true histiocytic neoplasia, and allow for quantitation of macrophages infiltrating lymphomas and other solid tumors.