CircBCAR3 sponges miR-27a-3p and mediates ferroptosis in human B-prolymphocytic leukaemia cells via SLC7A11.

B-lymphocytic leukaemia is one of the most commonly diagnosed blood malignancies, and our knowledge of B-prolymphocytic leukaemia remained barely comprehensive. CircRNAs and miRNAs were identified of important regulatory roles in tumours. This study focused on the possibly existing interaction of circBCAR3 and miR-27a-3p, and downstream molecules thereafter in B-prolymphocytic leukaemia cells. CircBCAR3 and miR-27a-3p expression was evaluated in JVM-2 cell line and normal lymphocytes. Dual-luciferase luminescence assay was conducted for validation of circBCAR3 and miR-27a-3p interaction, as well as western blot and flow cytometry for evaluation and validation of their association with SLC7A11, reactive-oxygen species and Fe2+ regarding ferroptosis. CircBCAR3 were upregulated in JVM-2 cells and were reversely correlated with the expression of miR-27a-3p. CircBCAR3 targeted at miR-27a-3p and was consequently associated with SLC7A11 expression positively, inhibiting ferroptosis and peroxidative damage in JVM-2 cells. This study identified a circBCAR3-miR-27a-3p-SLC7A11 axis regulating ferroptosis and peroxidation of B-prolymphocytic leukaemia cells which might be a key mechanism facilitating the survival of tumour cells. However, further validation based on more diverse cell lines and animal models might be required.

[Clinicopathologic study of 15 splenectomy specimens of patients with hairy cell leukemia].

OBJECTIVE: To investigate the clinicopathologic features, diagnosis, differential diagnosis and the prognosis of hairy cell leukemia (HCL). METHODS: Fifteen splenectomy specimens of HCL patients were investigated retrospectively using HE and immunohistochemistry in correlation with the follow-up information. RESULTS: (1) The male to female ratio was 2.75:1, age ranged from 36 to 68 years with a median of 47 years. The most consistent clinical feature at presentation was marked splenomegaly (100%). Other symptoms included anemia (80.0%), thrombocytopenia (60.0%), leucocytosis (53.3%), pancytopenia (20.0%) and the absence of B-symptom. (2) The proportion of hairy cells was (14.6 +/- 7.2)% in periphery blood and (47.3 +/- 23.8)% in bone marrow. The positive rate of TRAP assay was 62.5% in bone marrow; 85.7% for TPA test and the detection rate for RLC was 25% by transmission electric microscopy. The frequency of bone marrow involvement was 100%. (3) The average weight of 15 spleens was (3012 +/- 1974) g. The size of 6 spleens ranged from 16 cm x 10 cm x 5 cm to 32 cm x 20 cm x 14 cm. The white pulp of spleen showed a characteristic atrophy feature or even absent due to leukemic infiltration, predominantly involving the red pulp with some sinusoidal pattern. "Blood pool" change was an infrequent feature (3/15 cases). The nuclei of leukemic cells were round (13 cases) or bean-shaped (2 cases), nucleoli inconspicuous or disappeared. The abundant cytoplasm and prominent cell border resulted in a "fried egg" appearance. By immunohistochemistry, leukemic cells were positive for CD45RA, CD20, PAX-5, CD25, CD11c, Annexin A1 and cyclinD1, but negative for CD3 and CD43. (4) 13 cases (86.7%) have been followed-up and all are alive. Among them, 9 cases are living well more than 5 years and 7 more than 10 years. CONCLUSIONS: Splenomegaly is frequently the first manifestation of patients with HCL and occurred predominantly in the middle to elderly adults. Definite diagnosis of HCL requires a combined histological and immunohistochemical assessment of the splenectomy specimen, bone marrow biopsy and aspirate.

[Clinical and laboratory prognostic parameters for leukemic types of chronic lymphoproliferative diseases]. / Klinicki i laboratorijski prognosticki pokazatelji kronicnih leukemijskih limfoproliferativnih bolesti.

AIM: The aim of the study was to identify the clinical and laboratory (hematologic, biochemical and morphological) prognostic parameters of chronic leukemic lymphoproliferative diseases (CLLPD). METHODS: The study included 155 CLLPD patients. Analysis was performed in the overall CLLPD population and separately in a subgroup of patients with B chronic lymphocytic leukemia with variants (B-CLL+V) including typical B chronic lymphocytic leukemia (B-CLL), mixed chronic lymphocytic leukemia and prolymphocytic leukemia (CLL/PLL), and a variant of chronic lymphocytic leukemia with lymphoplasmocytoid differentiation (CLL/IMC). Kaplan-Meier method (Statistica 7.1) was used on survival analysis. RESULTS: Male patients older than 62 (p=0.03991), female patients (p=0.02871), patients not receiving antitumor therapy on study entry (p=0.01902) and patients not treated for CLLPB upon study entry (p=0.04076) showed better survival rate. Older patient predominated in the group requiring no antitumor therapy (p=0.019247). Analyis of sex distribution yielded an equal male to female ratio in the overall CLLPD population and B-CLL+V subgroup. Mann-Whitney U-test was used to assess the clinical significance of quantitative parameters related to patient age and sex. The level of bilirubin, the size of cervical lymph nodes and doubling of peripheral blood lymphocytosis (DTL) were lower in the group of older patients (>60 years). Men had higher levels of hemoglobin, bilirubin, SGOT and creatinine, and larger spleen and liver. Statistically significant survival differences were recorded for 16 of 20 clinical parameters. Patients older than 60, female patients and patients receiving no antitumor therapy showed better survival. Lower clinical stage according to Rai and Binet and total tumor mass (TTM) lower than 9 indicated better prognosis, whereas patients with spleen enlargement and multiple regions involved with lymph node enlargement showed poorer survival. B-CLL+V patients and patients free from doubling of total tumor (DTM) or of absolute lymphocyte count (DTL) within 12 months had better survival than the overall CLLPD patient population. A statistically significant survival difference was recorded for 5 of 15 bone marrow (BM) parameters tested: normal and less cellular BM puncture specimen, >70% of all lymphatic cells, >16% of atypical lymphatic cells, and >18% of granulocytes in myelogram indicated better prognosis. Poorer disease outcome was associated with interstitial and nodular infiltration found on bone biopsy. Ten of 20 hematologic parameters were found to be statistically significant. Poorer prognosis was associated with red blood cell count <2.5 x 10(12)/L, leukocyte count >100 x 10(9)/L, reticulocyte count >5/10(3) E, hemoglobin <100 g/L and iron <15 mol/L. Better survival was associated with absolute count of total lymphatic cells <100 x 10(9)/L and absolute count of atypical lymphatic cells <5 x 10(9)/L in peripheral blood; <10% of all atypical lymphatic cells, >5.1% monocytes and >10.1% granulocytes in differential blood count. Statistically significant survival differences were found for 10 of 20 biochemical parameters tested. Poorer survival was recorded in patients with LDH >300 U/L, SGOT >24 U/L, calcium <2.3 mmol/L, total protein <66.1 g/L, albumin <40 g/L, alpha2 globulin<5.9 g/L, beta globulin <7.3 g/L, y globulin <9 g/L and IgG <10 g/L. Better prognosis was only indicated by lower levels of IgM (<0.91 g/L). CONCLUSION: Careful clinical examination is an important step on assessing the extent and progression of the disease, and a major chain on tailoring individualized therapeutic approach, along with clinical stages according to Rai and Binet, CLLPD subtype and progression factors (DTM and DTL). Laboratory parameters (hematologic and biochemical) as objective quantitative parameters obtained by simple venipuncture, in contrast to the 'researcher-dependent' ones, increase the utilization of some of these parameters as risk factors in CLL.

High TCL1 expression and intact T-cell receptor signaling define a hyperproliferative subset of T-cell prolymphocytic leukemia.

The T-cell leukemia 1 (TCL1) oncoprotein is overexpressed by chromosomal rearrangement in the majority of cases of T-cell prolymphocytic leukemia (T-PLL). In vitro, TCL1 can modulate the activity of the serine-threonine kinase AKT, a downstream effector of T-cell receptor (TCR) signaling. In a series of 86 T-PLL tumors, we show that expression of TCR, and levels of TCL1 and activated AKT are adverse prognostic markers. High-level TCL1 in TCR-expressing T-PLL is associated with higher presenting white blood cell counts, faster tumor cell doubling, and enhanced in vitro growth response to TCR engagement. In primary tumors and TCL1-transfected T-cell lines, TCR engagement leads to rapid recruitment of TCL1 and AKT to transient membrane activation complexes that include TCR-associated tyrosine kinases, including LCK. Pharmacologic inhibition of AKT activation alters the localization, stability, and levels of these transient TCL1-AKT complexes and reduces tumor cell growth. Experimental introduction and knockdown of TCL1 influence the kinetics and strength of TCR-mediated AKT activation. We propose that in T-PLL, TCL1 represents a highly regulated, targetable modulator of TCR-mediated AKT growth signaling.

T-cell prolymphocytic leukemia: an aggressive T cell malignancy with frequent cutaneous tropism.

BACKGROUND: T-cell prolymphocytic leukemia (T-PLL), formerly categorized as T-cell chronic lymphocytic leukemia, is a rare and aggressive hematologic malignancy. Although the skin is characteristically involved, it is not a well-recognized entity in the dermatologic literature. METHODS: Six cases of cutaneous T-PLL are presented from a clinical, light microscopic, and phenotypic perspective. RESULTS: The patient population comprised 2 women and 4 men, with a mean age of 69.8 years. The disease was associated in all with skin involvement with facial preference; edema, purpura, and lesional symmetry were characteristic. The skin biopsies demonstrated a largely non-epidermotropic angiocentric lymphocytic infiltrate with accompanying hemorrhage. The cells showed irregular- to reniform-shaped nuclei with small nucleoli and eosinophilic rims of cytoplasm. Phenotypic studies revealed three prevailing profiles: CD4 dominant in 4, CD8 dominant in one, and co-expression of CD4 and CD8 in one. CD3 loss was seen in one case. All expressed T-cell leukemia 1 (TCL-1) and CD7; cutaneous lymphocyte antigen expression was discernible in a dot-like perinuclear array. All cases tested excluding one expressed TCL-1 and CD52. In two cases tested, T-cell receptor beta rearrangements were observed. Cytogenetic studies demonstrated a paracentromeric chromosome 14 inversion. Polysomy 8 and MYC amplification was seen in one case, manifesting an aggressive clinical course. Four patients died from their disease within 18 months of diagnosis. LIMITATIONS: Cytogenetic MYC amplification, FISH, and TCR beta studies were conducted on each of 2 cases, respectively, due to limitations of tissue block samples and/or peripheral blood. cMYC translocation studies were conducted on 3 of the 6 cases, again due to limitations imposed by the tissue samples on the cases. The last case was recently diagnosed and, therefore, long-term follow-up is not possible. CONCLUSION: T-PLL is a distinctive post-thymic T-cell malignancy with frequent cutaneous tropism. A diagnosis is possible in almost all cases based on characteristic clinical, light microscopic, phenotypic, and cytogenetic features. While a chromosome 14 inversion is highly characteristic, additional inherent cytogenetic differences, such as trisomy 8 with CMYC over-amplification, may account for some case to case variation in clinical course.

Periorbital edema as the initial presentation of T-cell prolymphocytic leukemia.

A 57-year-old woman presented with a history of progressive bilateral upper and lower eyelid edema. Laboratory tests revealed T-cell prolymphocytic leukemia. Despite systemic treatment, she died 2 weeks after presentation. This life-threatening disorder should be added to the differential diagnosis of eyelid edema.

D cyclins in CD5+ B-cell lymphoproliferative disorders: cyclin D1 and cyclin D2 identify diagnostic groups and cyclin D1 correlates with ZAP-70 expression in chronic lymphocytic leukemia.

We analyzed protein expression of cyclin D1, cyclin D2, and cyclin D3 using high-resolution enzymatic amplification staining and flow cytometry in the neoplastic cells from 80 patients with CD5+ B-cell lymphoproliferative disorders. The D cyclins were expressed differentially in chronic lymphocytic leukemia (CLL), prolymphocytic leukemia (PLL), and mantle cell lymphoma (MCL) with strong staining of cyclin D1 and D2 in MCL, strong staining of cyclin D1 but weak staining of cyclin D2 in 4 of 5 PLLs, and low-level staining for both cyclins in most CLLs. No correlation between cyclin D1 and D2 and growth rates or CD38 expression was observed. However, cyclin D1 levels were significantly higher in ZAP-70+ CLL cases, although no association between ZAP-70 and cyclin D2 was detected. The results indicate that flow cytometric analysis of D cyclins may help in classification of CD5+ B-cell lymphoproliferative disorders.

T-cell prolymphocytic leukemia: a single-institution experience.

BACKGROUND: T-cell prolymphocytic leukemia is an uncommon, aggressive, mature T-cell leukemia characterized by proliferation of T-cell lymphocytes. The recent availability of modern immunophenotypic and molecular tools has allowed a better distinction of this disorder from its B-cell counterpart and other mature T-cell leukemias. PATIENTS AND METHODS: The clinical, pathologic, and cytogenetic features of 57 patients with T-PLL who were evaluated at the Department of Leukemia, M. D. Anderson Cancer Center (MDACC) from 1986 to 2004 were examined. RESULTS: The most common cytogenetic abnormality was inv(14)(q11;q32), which was present in 7 patients. In all 7 patients, this abnormality was associated with other chromosomal aberrations. Patients treated with alemtuzumab at MDACC had a significantly better response rate (P = 0.02) and survival rate (P = 0.002). There were no significant differences in survival based on Tcl-1 expression or different patterns of CD4 and CD8 expression. CONCLUSION: Treatment with alemtuzumab results in higher response rates and a better survival rate in patients with T-cell prolymphocytic leukemia.

Histopathology of the spleen in T-cell large granular lymphocyte leukemia and T-cell prolymphocytic leukemia: a comparative review.

We review retrospectively the spleen histology in 8 patients with T-cell large granular lymphocyte (LGL) leukemia and 4 with T-cell prolymphocytic leukemia (T-PLL) to identify characteristic patterns of involvement and to distinguish such patterns from those described in other low grade B- and T-cell malignancies. Moderate splenic enlargement with red pulp expansion due to lymphocytic infiltration was characteristic of LGL leukemia. Abnormal lymphocytes expressed cytotoxic granule proteins and were consistently CD45RO and CD5 negative in contrast to normal red pulp T cells. This infiltration respected anatomic boundaries with encroachment but no invasion of white pulp areas. Unlike in hairy cell leukemia, the main differential diagnosis for red pulp lymphocytosis, the white pulp was not only preserved in T-cell LGL leukemia but showed germinal center hyperplasia with expansion of the mantle zones. By comparison, T-PLL spleens showed marked red pulp lymphoid infiltration by medium-sized cells with irregular nuclei and prominent eosinophilic nucleoli. T-PLL lymphocytes, unlike LGLs, were more invasive, infiltrating the spleen capsule as well as white pulp areas. T-cell prolymphocytes did not express cytotoxic granule proteins or NK-cell markers, were CD5+, CD45RO+ like normal spleen T cells, were CD2+, CD3+, CD45+, CD43+, TCRbeta+, but CD25-, CD30-, ALK-1-, TRAP-, DBA44-, and TdT-. Expression of CD4 and CD8 in these cells mirrored that of circulating T-PLL cells. These observations on the morphologic and immunohistochemical appearances of the spleen in T-cell LGL leukemia and T-PLL may aid diagnosis of these uncommon T-cell disorders, particularly T-cell LGL leukemia, where presentation may be cryptic and where unique pathognomonic features, are absent.

T-cell prolymphocytic leukemia involving extramedullary sites.

T-cell prolymphocytic leukemia (T-PLL) can involve extramedullary sites, but the diagnosis is usually established by examination of blood and bone marrow. As a result, the histologic findings at extramedullary sites are poorly documented in the literature. We describe 19 extramedullary biopsy specimens from 14 patients with T-PLL. Skin (n = 10) was the most common site biopsied. T-PLL surrounded dermal blood vessels and appendages (n = 6), diffusely replaced dermis (n = 3), or formed a subcutaneous mass (n = 1). Other extramedullary sites included liver and lymph nodes (3 each) and spleen, lung, and cecum (1 each). In liver and lymph nodes, the neoplasm predominantly involved portal tracts and paracortex, respectively. Cytologically, the T-PLL cells were round (n = 16) or Sezary cell-like (n = 3). Nucleoli were observed in a subset of cells in 8 specimens and were prominent in 3 specimens. Immunostaining for T-cell leukemia-1 (TCL-1) was positive in specimens from 9 (64%) of 14 patients. We conclude that the prolymphocytoid features of T-PLL cells can be difficult to detect in routinely stained sections of extramedullary biopsy specimens. TCL-1 expression can aid in diagnosis at extramedullary sites.

Conjunctival involvement with T-cell prolymphocytic leukemia: report of a case and review of the literature.

T-cell prolymphocytic leukemia is a rare and highly aggressive hematological neoplasm. A patient with T-cell prolymphocytic leukemia presented with bilateral perilimbal conjunctival infiltrates. Conjunctival biopsy showed aggregates of large atypical lymphocytes in the substantia propria with a concentration of atypical cells in the perivascular areas. Immunophenotyping of the malignant cells identified an abnormal clonal T-cell population consistent with T-cell prolymphocytic leukemia. A literature review of all reports of conjunctival involvement with leukemia was performed. The three cases of ocular prolymphocytic leukemia, including the one case of ocular T-cell prolymphocytic leukemia, are discussed in detail as well as 14 reported clinical cases of biopsy-proven conjunctival leukemia. The majority of cases occurred in the setting of acute leukemia, and conjunctival involvement was frequently a presenting sign of the disease or signified disease relapse. Conjunctival involvement with leukemia was consistent with good visual acuity; however, it portended a poor prognosis.

Case report: mantle cell lymphoma, prolymphocytoid variant, with leukostasis syndrome.

A 76-year-old man presented with leukostasis syndrome, including oculodynia, blurred vision, and visual field defects, due to mantle cell lymphoma, prolymphocytoid variant, with marked leukocytosis, 1227 x 10(9)/l. He had splenomegaly but no lymphadenopathy or hepatomegaly. The tumor cells were CD5+, CD19+, CD20+, FMC-7+, and kappa light chain restricted. Immunohistochemistry showed expression of p53 and of cyclin D1. Fluorescent in situ hybridization demonstrated t(11;14) with translocation between CYCLIN D1 and the immunoglobulin heavy-chain genes. The patient received leukapheresis and aggressive chemotherapy, but the leukocyte count remained above 100 x 10(9)/l. The patient's condition rapidly deteriorated with lymphomatous infiltration of his lungs and soft tissues, and he expired 6 months after diagnosis. While it is known that mantle cell lymphoma may have a leukemic phase, the degree of leukocytosis in this case exceeds that previously reported in the literature and resulted in a clinical syndrome of leukostasis.

Regulation of MHC class II expression in human T-cell malignancies.

Expression of major histocompatibility complex (MHC) class II molecules in human activated T cells is under normal circumstances regulated exclusively by the CIITA-PIII subtype of the class II transactivator (CIITA). In this study, we show that the absence of MHC class II expression in leukemic T cells was due to a lack of expression of CIITA, whereas in T-lymphoma cells, expression of CIITA correlated with expression of MHC class II. Interestingly, activation of a CIITA-promoter (P)III-reporter construct was not affected in leukemic T cells. This revealed that the absence of endogenous CIITA expression was not caused by a lack of transcription factors critical for CIITA-PIII activation but suggests the involvement of an epigenetic silencing mechanism. Subsequent analysis showed that the lack of human leukocyte antigen-DR (HLA-DR) expression correlated with hypermethylation of CIITA-PIII in leukemic T-cell lines and in primary T-cell acute lymphoblastic leukemia (T-ALL) and a T-cell prolymphocytic leukemia (T-PLL). Treatment of leukemic T-cell lines with a demethylation agent showed re-expression of CIITA-PIII and HLA-DRA. Furthermore, in vitro methylation of CIITA-PIII and subsequent assessment of CIITA-PIII activity in Jurkat leukemic T cells resulted in reduction of constitutive and CREB-1 (cyclic adenosine monophosphate [cAMP]-response element binding protein 1)-induced promoter activity. Together, these results argue for an important role of DNA hyper-methylation in the control of CIITA expression in leukemic T cells.

The expression of PRAME in chronic lymphoproliferative disorders.

The PRAME gene encodes an antigen recognized by autologous T lymphocytes and is expressed in trophoblasts, testis and frequently in human solid cancers and acute leukemias, making it a candidate for immunotherapy and for detecting MRD. We demonstrate expression of PRAME by RT-PCR in the peripheral blood or bone marrow of 26% of 58 patients with CLD (38 cases of CLL, 4 cases of PLL and 16 cases of NHL). Seven out 16 cases of MCL, 2 out 4 of PLL and 6 cases of CLL demonstrated some degree of gene expression. Thus, CLD are among the hematopoietic malignancies for which PRAME may be the target of immunological therapy or used to evaluate MRD. The stronger and more frequent expression of PRAME in MCL is apparently an additional distinguishing feature on this group of lymphoproliferative disorders.

TCL1 expression in plasmacytoid dendritic cells (DC2s) and the related CD4+ CD56+ blastic tumors of skin.

Initially considered to be of natural killer (NK)-cell origin, CD4+ CD56+ blastic tumors (BTs) of skin have recently been proposed to be of dendritic cell lineage. We have previously described BTs with transformation to myelomonocytic leukemia. Here we report expression of the lymphoid proto-oncogene TCL1 in 10 (83%) of 12 BTs and in lymph node plasmacytoid dendritic cells (DC2s). TCL1 was also expressed in myelomonocytic blasts of 3 transformed BT cases but not in true NK-cell tumors (n = 18), de novo acute myelomonocytic leukemias (1 of 14, 7%), or mature T-cell malignancies (1 of 112, < 1%), with the exception of T-prolymphocytic leukemia (T-PLL). All BT cases were also positive for the DC2-associated marker CD123. These results further support derivation of BTs from DC2s, and demonstrate that TCL1 expression in this tumor is common to the immature blastoid, lymphoid-appearing, and subsequent myelomonocytic phases of this disease.

TCL-1, MTCP-1 and TML-1 gene expression profile in non-leukemic clonal proliferations associated with ataxia-telangiectasia.

We analyzed the role of 4 genes, TCL-1, MTCP-1, TML-1 and ATM, in the early pathogenesis of T cell leukemia, with particular interest in the characteristics of long-standing non-leukemic clonal proliferations in ataxia-telangiectasia (A-T) patients. Five patients were studied: 4 patients had A-T (2 of whom had non-leukemic clonal proliferations [ATCP]), 1 had B cell lymphoma and 1 had T-ALL; a fifth patient with T-PLL did not have A-T. We measured the levels of expression for TCL-1, MTCP-1 and TML-1. TCL-1, not expressed in unstimulated mature T cells, was upregulated in the peripheral blood leukocytes (PBL) of the 2 A-T patients with ATCP. It was also expressed in the malignant cells of the A-T patient with B cell lymphoma and the T-PLL cells of the patient without A-T. In the same cells, MTCP-1 type A was expressed equally in all 5 patients, as well as in the controls; MTCP-1 type B transcripts were not observed. TML-1, also not expressed in unstimulated T cells, was expressed in the PBL of one A-T patient with ATCP and in the leukemic cells of the non-A-T T-PLL patient. These expression patterns were compared to cellular immunophenotypes. The non-leukemic clonal T cell populations had the characteristics of immature T cells. We conclude that TCL-1 and TML-1 play a role in cell proliferation and survival but are not pivotal genes in the progression to malignancy, even when the ATM gene is mutated. Additional genetic alterations must occur to initiate tumorigenesis.

Typical and atypical chronic lymphocytic leukemia differ clinically and immunophenotypically.

We compared the features of 17 cases of atypical chronic lymphocytic leukemia (aCLL) with those of a clinical control group of 24 cases of CLL. Quantitative flow cytometric data, available for 12 cases, were compared with an immunophenotypic control group of 58 cases using a relative fluorescence indexfor CD5, CD23, CD79b, and surface immunoglobulin light chain (sIg). Compared with the clinical control group, patients with aCLL had a higher mean WBC count and a lower platelet count. Patients with aCLL had a significantly higher probability of disease progression. Compared with an immunophenotypic control group of 58 CLL cases, 12 cases of aCLL demonstrated significantly higher expression of CD23. There was no significant difference in expression of sIg, CD79b, or CD5 between the groups. CD38 expression was noted in only 1 (9%) of 11 tested cases; 2 (18%) of 11 cases had trisomy 12. aCLL can be distinguished from typical CLL morphologically, clinically, and immunophenotypically. Atypical morphologic features in CLL seem to be a marker of aggressive clinical behavior.

Immunophenotype changes and loss of CD52 expression in two patients with relapsed T-cell prolymphocytic leukaemia.

T-cell prolymphocytic leukaemia (T-PLL) is an aggressive disease often resistant to conventional chemotherapy. Long lasting remissions with the monoclonal antibody CAMPATH-1H (anti-CD52) have been documented. We describe two unusual T-PLL patients treated successfully first with CAMPATH-1H in whom, at the time of relapse, the cells underwent a phenotypic switch with loss of CD52 expression. In one of them, cytogenetic analysis demonstrated the same chromosome abnormalities in the cells at diagnosis and relapse. The reasons for the immunophenotypic changes are unknown but it is likely that loss of CD52 antigen expression contributed to the resistance to CAMPATH-1H in one of the patients when re-treated.

Differential diagnosis of malignant lymphomas and related disorders by specific pattern of expression of immunophenotypic markers revealed by multiparameter flow cytometry (Review).

The introduction of monoclonal antibodies (mAbs) for cell immunophenotyping and use of flow cytometry with the progressively improving software for multivariate analyses have revolutionized the diagnosis and influenced the classification of hematologic neoplasms. In this review we focus on the practical application of flow cytometry in the diagnosis and classification of malignant lymphomas and related lymphoproliferative disorders with special emphasis on differential diagnosis. A general approach to the utilization of flow cytometry (FC) in hematopathology with an algorithm to diagnose the most common neoplasms is presented. We discuss precursor B-cell neoplasms, mature B-cell neoplasms (SLL/CLL, mantle cell lymphoma, marginal zone lymphoma, hairy cell leukemia, diffuse large B-cell lymphoma, plasma cell dyscrasias and lymphomas with plasmacytic differentiation), precursor T-lymphoblastic leukemia and mature (peripheral) T-cell neoplasms, including T-SLL/PLL, anaplastic cell lymphomas and large granular cell leukemia/lymphoma. The text is accompanied by characteristic FC scatterplots of the discussed entities.