Neoplasms of histiocytes and dendritic cells are rare, and their phenotypic and biological definition is incomplete. Seeking to identify antigens detectable in paraffin-embedded sections that might allow a more complete, rational immunophenotypic classification of histiocytic/dendritic cell neoplasms, the International Lymphoma Study Group (ILSG) stained 61 tumours of suspected histiocytic/dendritic cell type with a panel of 15 antibodies including those reactive with histiocytes (CD68, lysozyme (LYS)), Langerhans cells (CD1a), follicular dendritic cells (FDC: CD21, CD35) and S100 protein. This analysis revealed that 57 cases (93%) fit into four major immunophenotypic groups (one histiocytic and three dendritic cell types) utilizing six markers: CD68, LYS, CD1a, S100, CD21, and CD35. The four (7%) unclassified cases were further classifiable into the above four groups using additional morphological and ultrastructural features. The four groups then included: (i) histiocytic sarcoma (n=18) with the following phenotype: CD68 (100%), LYS (94%), CD1a (0%), S100 (33%), CD21/35 (0%). The median age was 46 years. Presentation was predominantly extranodal (72%) with high mortality (58% dead of disease (DOD)). Three had systemic involvement consistent with 'malignant histiocytosis'; (ii) Langerhans cell tumour (LCT) (n=26) which expressed: CD68 (96%), LYS (42%), CD1a (100%), S100 (100%), CD21/35 (0%). There were two morphological variants: cytologically typical (n=17) designated LCT; and cytologically malignant (n=9) designated Langerhans cell sarcoma (LCS). The LCS were often not easily recognized morphologically as LC-derived, but were diagnosed based on CD1a staining. LCT and LCS differed in median age (33 versus 41 years), male:female ratio (3.7:1 versus 1:2), and death rate (31% versus 50% DOD). Four LCT patients had systemic involvement typical of Letterer-Siwe disease; (iii) follicular dendritic cell tumour/sarcoma (FDCT) (n=13) which expressed: CD68 (54%), LYS (8%), CD1a (0%), S100 (16%), FDC markers CD21/35 (100%), EMA (40%). These patients were adults (median age 65 years) with predominantly localized nodal disease (75%) and low mortality (9% DOD); (iv) interdigitating dendritic cell tumour/sarcoma (IDCT) (n=4) which expressed: CD68 (50%), LYS (25%), CD1a (0%), S100 (100%), CD21/35 (0%). The patients were adults (median 71 years) with localized nodal disease (75%) without mortality (0% DOD). In conclusion, definitive immunophenotypic classification of histiocytic and accessory cell neoplasms into four categories was possible in 93% of the cases using six antigens detected in paraffin-embedded sections. Exceptional cases (7%) were resolvable when added morphological and ultrastructural features were considered. We propose a classification combining immunophenotype and morphology with five categories, including Langerhans cell sarcoma. This simplified scheme is practical for everyday diagnostic use and should provide a framework for additional investigation of these unusual neoplasms.

Despite advances in immunohistochemistry and molecular biology, the distinction between classical Hodgkin's lymphoma and related diseases such as nodular lymphocyte-predominant Hodgkin's disease, T-cell rich large B-cell lymphoma or anaplastic large cell lymphoma has remained difficult in rare cases. Lack of clear-cut diagnostic criteria represents a problem for both the pathologist and the clinician. To delineate this 'grey zone' between classical Hodgkin's lymphoma and non-Hodgkin's lymphoma (NHL) and to develop criteria for classification of such cases, 12 expert hematopathologists each submitted one to five borderline cases to a workshop. Cases were reviewed and classified at a multiheaded microscope and criteria were established for the diagnosis of questionable cases. Well established entities such as classical Hodgkin's lymphoma, anaplastic large-cell lymphoma and TCRBCL were defined more strictly and cases with unusual morphology or antigen expression could be identified. A distinctive subset of cases representing mediastinal large B-cell lymphomas with features of Hodgkin's lymphoma was identified.

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Previous studies have suggested that desmopressin may reduce the bleeding diathesis that often complicates open-heart surgery. To pursue this question further, we performed a double-blind, randomized, placebo-controlled trial to determine whether the previously reported beneficial effect of desmopressin on hemostasis during complex cardiac surgery was applicable to all elective cardiac surgical procedures involving cardiopulmonary bypass. In 150 consecutive patients, most of whom underwent primary coronary-artery bypass grafting, we compared the effects of intravenous desmopressin (0.3 microgram per kilogram of body weight) with those of saline placebo on postoperative blood loss and the need to replace blood products. The median amount of blood lost within the first 24 hours after operation was similar in the desmopressin and placebo groups (865 vs. 738 ml; P = 0.26). The postoperative use of blood replacement products did not differ significantly between the groups (1025 ml [95 percent confidence interval, 300 to 4140 ml] in the desmopressin group and 860 ml [247 to 5346 ml] in the placebo group). Desmopressin is believed to exert its hemostatic effect by releasing von Willebrand factor. The level of ristocetin cofactor, a functional index of the level of von Willebrand factor, was increased approximately twofold from base line in both treatment groups 90 minutes and 24 hours after the administration of medication. Similarly, the levels of von Willebrand factor multimers increased uniformly in both groups. These findings may be consistent with a normal stress response of von Willebrand factor to major surgery and could explain our failure to detect a therapeutic effect of desmopressin. We conclude that the majority of patients who undergo elective cardiac surgery receive no hemostatic benefit from the use of desmopressin.

We demonstrated Bcl-2 protein expression and t(14;18)(q32;q21) in a significant minority of cases, suggesting a relationship with NFL. It remains to be seen whether, on longer follow-up, there is any clinical difference in cases with and without t(14;18)(q32;q21).

In contrast to the commonly indolent clinical behavior of nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), T cell/histiocyte rich large B cell lymphoma (THRLBCL) is frequently diagnosed in advanced clinical stages and has a poor prognosis. Besides the different clinical presentations of these lymphoma entities, there are variants of NLPHL with considerable histopathologic overlap compared to THRLBCL. Especially THRLBCL-like NLPHL, a diffuse form of NLPHL, often presents a histopathologic pattern similar to THRLBCL, suggesting a close relationship between both lymphoma entities. To corroborate this hypothesis, we performed gene expression profiling of microdissected tumor cells of NLPHL, THRLBCL-like NLPHL and THRLBCL. In unsupervised analyses, the lymphomas did not cluster according to their entity. Moreover, even in supervised analyses, very few consistently differentially expressed transcripts were found, and for these genes the extent of differential expression was only moderate. Hence, there are no clear and consistent differences in the gene expression of the tumor cells of NLPHL, THRLBCL-like NLPHL and THRLBCL. Based on the gene expression studies, we identified BAT3/ BAG6, HIGD1A, and FAT10/UBD as immunohistochemical markers expressed in the tumor cells of all three lymphomas. Characterization of the tumor microenvironment for infiltrating T cells and histiocytes revealed significant differences in the cellular composition between typical NLPHL and THRLBCL cases. However, THRLBCL-like NLPHL presented a histopathologic pattern more related to THRLBCL than NLPHL. In conclusion, NLPHL and THRLBCL may represent a spectrum of the same disease. The different clinical behavior of these lymphomas may be strongly influenced by differences in the lymphoma microenvironment, possibly related to the immune status of the patient at the timepoint of diagnosis.

We have used a single-cell based polymerase chain reaction (PCR) amplification technique to examine the gene expression pattern in single Hodgkin's and Reed-Sternberg (H&RS) cells from seven patients with Hodgkin's disease. Single cells were isolated from lymph nodes obtained at diagnosis (5 of 7 patients) or in first or second relapse (2 of 7 patients). Gene expression was examined by hybridization to a panel of 22 cDNA probes. Forty-nine H&RS cells (and 23 CD3+ or CD20+ lymphocytes as controls) from four patients with nodular sclerosing Hodgkin's disease (HD) and one patient each with lymphocyte predominant and mixed-cellularity HD were successfully analyzed by PCR. This analysis provides evidence that single H&RS cells can coexpress genes characteristic of several hematopoietic lineages (monocytes and lymphocytes). Genes characteristic of activated lymphoid cells are expressed in most H&RS cells. Heterogeneity of expression for certain genes between different cases was found and may eventually define molecular subgroups of HD. These findings indicate that H&RS cells of HD resemble activated hematopoietic cells. Phenotypically similar cells from different cases exhibit characteristic molecular differences. In one patient, 5 of 7 single RS cells showed identical p53 cDNA mutations at codon 246 on specific reverse transcriptase [RT]-PCR and sequencing of exons 5 through 8. The novel experimental approach may provide a valuable tool for understanding the molecular events in newly diagnosed Hodgkin's disease and progression of the disease.

We studied 25 T-cell chronic lymphocytic leukemia (T-CLL) cases collected over a 15-year period. Immunophenotypic analysis was performed in each case; 12 cases were evaluated by cytogenetics, and gene rearrangement studies were performed in 14 cases. The median age was 57 years with a male predominance (M:F, 15:10). The median presenting lymphocyte count was 36.3 x 10(9)/L (range, 3.9 to 438 x 10(9)/L). Fourteen patients (56%) had shotty adenopathy and ten (40%) had mild-to-moderate splenomegaly at presentation; four (16%) had erythematous skin lesions. The lymphocytes were predominantly small; some cases had a minor component of medium-sized cells (< 10%). The nuclear: cytoplasmic ratios were uniformly high with round to oval nuclei; however, a wide spectrum of nuclear outlines could be found, ranging from minimally to markedly convoluted. Nucleoli were either absent or small and inconspicuous. These lymphocytes did not have the morphology of prolymphocytes and did not contain cytoplasmic granules. Bone marrow infiltration was generally in an interstitial pattern; the degree of involvement ranged from 15% to 90%. Immunophenotyping showed that the lymphocytes were mature T-cells with a predominant CD4+ immunophenotype. Three cases displayed a CD8+ immunophenotype. The patients were treated with a variety of chemotherapeutic regimens with only a minimal response observed in two of 20 patients. We conclude that T-CLL is an uncommon chronic lymphoproliferative disorder (CLPD) that can be morphologically similar to B-CLL, is distinct from T- prolymphocytic leukemia, and has an aggressive clinical course that is refractory to therapy. It may also be difficult to distinguish T-CLL from other T-CLPD, especially the leukemic phase of peripheral T-cell lymphoma and some cases of Sezary syndrome.