Flow cytometric detection of CD79a expression in T-cell acute lymphoblastic leukemias

We evaluated the lineage specificity of CD79a in acute leukemias using 3-color flow cytometry in 58 consecutive cases. A panel of cell-surface antigens, including myeloid-associated markers, B-cell-associated markers, and T-cell-associated markers, was used. All cases of acute myeloid leukemia were CD79a-, whereas all cases of B-lineage acute lymphoblastic leukemia (ALL) were CD79a+. Three of 8 cases of T-cell ALL showed variable CD79a expression, indicating the presence of a blast subset expressing a relatively high level of CD79a. We investigated the clinical and pathologic characteristics of these 3 cases. All 3 cases had L1 or L2 morphology and expressed surface CD3. None of the other B-cell-associated markers were positive, although 1 case expressed CD13 and CD33. Uncommon random karyotypic abnormalities were identified in all 3 cases. Molecular studies demonstrated monoclonal gene rearrangement of T-cell receptor gamma in 2 of 3 cases. All 3 patients were 18 years old or younger; 1 patient did not enter remission, and 1 had disease relapse in 8 months. Our findings provide further support for the existence of a subset of T-cell ALL coexpressing CD3 and CD79a. Further study of the clinical and biologic significance of this subset may be warranted.     

Immunoreactivity of B-cell markers (CD79a, L26) in rare cases of extranodal cytotoxic peripheral T- (NK/T-) cell lymphomas.

The monoclonal antibodies L26 (CD20) and CD79a are very useful reagents for the immunohistochemical assessment of B-cell lineage in lymphoproliferative disorders. Although very few CD20-positive peripheral T-cell lymphomas (PTL) have been reported, comprehensive analyses of CD79a reactivity in extranodal PTL and NK/T-cell lymphomas have not been performed previously. This study investigated CD79a (clone JCB117) and CD20 reactivity in 94 extranodal non-B-cell lymphomas (enteropathy-type intestinal T-cell lymphoma [n = 52], nasal NK/T-cell lymphoma [n = 11], and primary cutaneous PTL [n = 31]) and in 17 cases of nodal PTL, unspecified. In four cases (enteropathy-type intestinal T-cell lymphoma [n = 3] and nasal NK/T-cell lymphoma [n = 1]), the majority of tumor cells stained for CD79a (all CD20 negative) and one cutaneous PTL, unspecified, was CD20 positive (CD79a negative). Extensive immunophenotyping and polymerase chain reaction-based molecular analyses revealed that all five B-cell marker-positive extranodal lymphomas had a cytotoxic phenotype and did indeed represent monoclonal peripheral T-cell proliferations. To minimize the risk of misinterpretation of lymphoma cell lineage, especially in cases of extranodal, lymphoproliferative disease, we suggest the use of both CD79a and CD20 in combination with a panel of antibodies reactive to T cells, such as betaF1 and CD5, and to T cells and NK cells, such as CD3, CD2, CD56, and TIA-1.     

Primary bony peripheral T-cell lymphoma mimicking nasal type NK/T-cell lymphoma: a case report

Primary bony lymphomas are rare, and nearly all are high-grade B-cell lymphomas. Natural killer (NK)/T-cell lymphomas are highly aggressive lymphomas of NK- or T-cell lineage with predominant extranodal presentation and are divided into nasal and nasal-type (extra-nasal). We report a primary bony peripheral T-cell lymphoma mimicking NK/T-cell lymphoma, nasal type. A 22-year-old Taiwanese male presented with a frontal skull bone mass noted for 3 weeks, and received craniectomy with tumor removal. His tumor showed extensive coagulative necrosis with angioinvasion by large lymphoma cells expressing CD2, CD8, CD16, CD43, CD45, CD45RO, CD56, T-cell intracellular antigen-1, and granzyme B, but not CD3, CD4, CD20, CD57, CD68, and betaF1. In situ hybridization for Epstein-Barr virus-encoded mRNA was negative. Polymerase chain reaction study of formalin-fixed tissue showed clonal rearrangement of the T-cell receptor-gamma chain gene. The diagnosis was peripheral T-cell lymphoma, unspecified subtype. The initial stage was I(EA). His lymphoma was refractory to chemotherapy, and bony metastases developed in the right iliac bone 2 months later. He died of disease after 6 months without autopsy. We emphasize the importance of detailed immunohistochemical and gene rearrangement studies for the classification of malignant lymphomas via a very rare primary bony lymphoma of peripheral T-cell subtype.     

Presence of restricted killer immunoglobulin-like receptor repertoire and monoclonal T-cell receptor gamma rearrangement as evidence of mixed NK/T-cell differentiation in a subset of sinonasal lymphomas

Most sinonasal lymphomas have a restricted killer immunoglobulin-like receptor (KIR) repertoire without a monoclonal T-cell receptor-gamma (TCR-gamma) rearrangement, implying an NK lineage. However, the lineage assignment of sinonasal lymphoma with a monoclonal TCR-gamma rearrangement is unclear because of its mixed NK/T phenotype. The possibility of a mixed NK/T lineage arises with the discovery of T cells with NK features, such as KIR(+) T cells or Valpha24(+) NKT cells. The former might transform into a T-cell lymphoma with both a monoclonal TCR-gamma rearrangement and a restricted KIR repertoire; the latter might give rise to a T-cell lymphoma with a monoclonal Valpha24 rearrangement and possibly a restricted KIR repertoire. To identify such mixed-lineage lymphomas, we undertook a survey of 15 consecutive sinonasal lymphomas and found six with both a restricted KIR repertoire and a monoclonal TCR-gamma rearrangement, consistent with KIR(+) T-cell lymphomas. Among these six cases, four female CD56(-)/CD44(-)/CD8(-)/CD45RO(+)/CD45RA(-) cases constituted a distinct group with a better prognosis than the rest of the male cases of sinonasal lymphomas. None of the six cases had a monoclonal Valpha24 repertoire, thus excluding a derivation from NKT cells. The predominance of KIR(+) T cells that normally function in chronic viral infections over Valpha24(+) NKT cells that typically recognize glycolipid antigens is consistent with the known association of Epstein-Barr virus infection with sinonasal lymphoma. The demonstration of mixed lineage in a mature lymphoid neoplasm is unusual and echoes the World Health Organization classification that placed NK-cell and T-cell lymphomas in a mixed group.     

Primary follicular large cell lymphoma of the testis in a child

Primary follicular lymphoma of the testis in childhood is extremely rare. To our knowledge, only 5 cases have been reported to date. We report a case in a 6-year-old boy who presented with painless right scrotal enlargement. Right radical orchiectomy revealed a follicular large cell lymphoma with diffuse areas confined to the testis and epididymis, clinical stage IE. Immunohistochemical stains demonstrated that the neoplastic cells were of B-cell lineage, positive for CD10, CD20, CD79a, and BCL-6. Staining for CD21 accentuated networks of dendritic reticulum cells within the nodules. The cells were negative for BCL-2, p53, and T-cell antigens. There was no evidence of the t(14;18) detected by polymerase chain reaction. The data suggest that follicular lymphoma of the testis in children has a different pathogenesis than follicular lymphoma in adults.     

Immunoperoxidase detection of CD10 in Precursor T-lymphoblastic lymphoma/leukemia: a clinicopathologic study of 24 cases

CONTEXT: CD10 was originally reported in non-T-cell lymphoblastic lymphomas/leukemias. It has since been identified, however, in a minority of cases of T-lympho-blastic lymphoma/leukemia and other hematopoietic and nonhematopoietic entities. The usual method for the detection of CD10 previously required fresh tissue. A new antibody for CD10 (56C6) in paraffin embedded tissue sections, however, has recently become available. OBJECTIVE: To study the expression of CD10 in paraffin sections of T-lymphoblastic lymphoma/leukemia using monoclonal antibody 56C6. DESIGN: Twenty-four cases of T-lymphoblastic lymphoma/leukemia in various anatomic sites were studied. Immunohistochemical analysis with CD10 and a panel of other hematolymphoid antibodies was performed in all 24 cases. Gene rearrangement studies for the T-cell receptor by the polymerase chain reaction were performed in 18 of 24 cases. RESULTS: All cases were positive with at least 2 T-cell markers. In 15 (63%) of 24 cases CD10 was positive. T-cell receptor gene rearrangement was detected in 10 of 18 cases. CONCLUSIONS: Immunodetection of CD10 in T-lympho-blastic lymphoma/leukemia using monoclonal antibody 56C6 is common. This finding is useful in the evaluation of T-cell neoplasms.     

T cell lymphoma co-expressing CD20

Haematological malignancies are currently classified by the WHO according to lineage, with stratification of non-Hodgkin lymphomas into B cell neoplasms, and T and NK cell neoplasms. Many laboratories routinely use CD20 and CD3 immunostains to identify B and T cell lymphomas respectively, with the use of additional immunomarkers where necessary.We report a case of an 84-year-old male with a peripheral lymphoma which stained positively with both CD3 and CD20. PCR of DNA extracted from paraffin embedded material was positive for clonal T cell receptor gene rearrangements but negative for clonal immunoglobulin gene rearrangement supporting a diagnosis of T cell lymphoma with aberrant CD20 positivity.This case is one of only a small number of reported cases of T cell lymphoma co-expressing CD20 and illustrates a potential pitfall in diagnosis. It emphasizes the need for 1) vigilant review of immunohistochemical stains to avoid misinterpretation and 2) the use of a wide immunohistochemical panel in lymphoma diagnosis with additional molecular studies where necessary.     

Testicular natural killer/t-cell lymphoma,nasal type,of true natural killer-cell origin

The majority of primary testicular lymphomas are of B-cell type. Other primary lymphomas are rarely encountered in the testes. Natural killer (NK)/T-cell lymphomas of nasal type are aggressive extranodal lymphomas associated with Epstein-Barr virus infection that are usually encountered in the upper aerodigestive tract. They also occur in the skin, soft tissue, and colon. Primary testicular NK/T-cell lymphomas are rarely reported. We describe the case of a 66-year-old Korean man who presented with right-sided painless testicular enlargement and underwent radical orchiectomy. Histologic examination revealed an angiocentric and angioinvasive infiltrate of medium to large tumor cells with moderately abundant pale pink cytoplasm and folded and indented pleomorphic nuclei. Paraffin immunohistochemical studies showed positivity of the tumor cells for CD45, TIA-1, granzyme B, CD56, and CD3 epsilon. In situ hybridization showed diffuse positivity for Epstein-Barr virus-encoding RNA. The results of gene rearrangement studies for the gamma chain of the T-cell receptor were negative. The results of paraffin immunohistochemical studies for CD20, CD8, CD45RO, beta f1, and ALK-1 were negative. An extensive workup showed no evidence of lymphoma outside the testes. We report a rare case of primary testicular NK/T-cell lymphoma of the nasal type of true NK-cell origin.     

Anti-CD20 monoclonal antibody treatment of human herpesvirus 8-associated, body cavity-based lymphoma with an unusual phenotype in a human immunodeficiency virus-negative patient

Human herpesvirus 8 (HHV-8), or Kaposi's sarcoma-associated herpesvirus, is a gammaherpesvirus first detected in Kaposi's sarcoma tumor cells and subsequently in primary effusion lymphoma (PEL) tumor cells and peripheral blood mononuclear cells from PEL patients. PEL has been recognized as an individual nosologic entity based on its distinctive features and consistent association with HHV-8 infection. PEL is an unusual form of body cavity-based B-cell lymphoma (BCBL). It occurs predominantly in human immunodeficiency virus (HIV)-positive patients but occasionally also in elderly HIV-negative patients. We describe a case of PEL, with ascites, bilateral pleural effusions, and a small axillary lymphadenopathy, in a 72-year-old HIV-negative man. PCR performed on a lymph node specimen and in liquid effusion was positive for HHV-8 and negative for Epstein-Barr virus. The immunophenotype of the neoplastic cells was B CD19+ CD20+ CD22+ with coexpression of CD10 and CD23 and with clonal kappa light chain rearrangement. The patient was treated with Rituximab, a chimeric (human-mouse) anti-CD20 monoclonal antibody. Thirteen months later, the patient continued in clinical remission. This is the first report of an HHV-8-associated BCBL in an HIV-negative patient in Argentina.     

A primary nipple lymphoma diagnosed by a modified fine‐needle aspiration method

Primary breast lymphomas are uncommon. All reported primary breast lymphomas were in the breast parenchyma. Here we reported the first case of primary nipple lymphoma in a 76‐year‐old woman initially diagnosed using a modified fine‐needle aspiration method. The aspirated material by this method had yielded adequate material for both cytomorphologic and flow cytometric analysis, as well as for molecular analysis of light chain rearrangement. In smears the atypical lymphocytes were predominantly middle‐sized with irregular nuclei. Scattered large centroblast or immunoblast‐like cells, a few reactive lymphocytes, histocytes, and few plasma cells were also observed. These findings suggested a low‐grade lymphoma that was further confirmed by flow cytometry (CD19+/CD3?, positive for cytoplasmic kappa light chain but negative for lambda light chain) and molecular analysis (monoclonal rearrangement of immunoglobulin kappa chain). Immunohistochemical stains performed on the excised specimen showed that the tumor cells were positive for CD20 and CD79a but negative for cytokeratin, CD3, CD5, CD10, CD23, CD43, CD45RO, bcl‐6, and cyclin‐D1. The Ki‐67 proliferation index was less than 20%. Taking these together, the case was diagnosed as a primary MALT lymphoma of the nipple. FNA usually provides a better cell morphology than tissue sections, but pathologists have to face the sampling error and lack of immunophenotype information when subtyping lymphoma issues using FNA. With the help of flow cytometry and molecular analysis, more and more trials haveproved the accuracy of FNA in diagnosis of lymphomas. Therefore, FNA could play an informative and diagnostic role indiagnosis of lymphoma. Diagn. Cytopathol. 2012. © 2011 Wiley Periodicals, Inc.     

Demonstration of distinct antigenic profiles of small B-cell lymphomas by paraffin section immunohistochemistry.

The immunoperoxidase technique was used with antibodies against B-cell-associated antigens, including CD20, CD79a, CD10, CD23, CD43, cyclin D1, bcl-2, and kappa and lambda immunoglobulin light chains on formalin-fixed and B5-fixed tissue sections of follicular, small lymphocytic, mantle cell, and marginal zone lymphomas. Results obtained with paraffin section immunohistochemistry for CD20, CD10, CD23, and kappa and lambda light chains were compared with results obtained with flow cytometry or frozen section immunohistochemistry. Cells in all of the lymphoma types were positive for CD20 and CD79a. The antigenic profiles of the B-cell lymphomas demonstrated in paraffin sections were lymphoma type distinctive. Intrafollicular lymphocytes in follicular lymphomas were positive for CD10 and bcl-2. Small lymphocytic lymphomas expressed CD43 and CD23 and were negative for CD10 and cyclin D1. Mantle cell lymphomas characteristically expressed CD43 and cyclin D1 and were negative for CD23 and CD10. Marginal zone lymphomas were negative for CD23, CD10, and cyclin D1. All of the antibodies performed better in B5-fixed tissues, but formalin-fixed tissue immunophenotypes were always similar to those obtained on the B5-fixed tissue. These results were possible using well-fixed tissue, various antigen retrieval strategies, paraffin section reactive primary antibodies, and sensitive detection systems. Paraffin section immunohistochemistry on sections of routinely fixed tissue can be used similarly to flow cytometry and frozen section immunohistochemistry when classifying the lymphomas of small B lymphocytes.     

An unusual case of peripheral T-cell lymphoma with CD56 positivity and angiocentric, angiodestructive morphology arising in the ileum

Natural killer cell and cytotoxic T-cell lymphomas are frequently difficult to distinguish because they share many common features, and yet it is important to make an accurate diagnosis because their prognoses differ. We report an unusual case of a white man with a CD56-positive T-cell lymphoma in the ileum. The histologic pattern was characterized by angioinvasion and angiodestruction. Immunohistochemical staining showed positive reactions to CD3, CD8, CD43, CD45RO, CD56, and T-cell intracellular antigen-1, but negative reactions to CD4, CD5, CD20, CD23, and CD57. Epstein-Barr virus (EBV) was not detected by EBV-latent membrane protein staining and EBV polymerase chain reaction technique. The T-cell receptor gamma chain gene was rearranged. According to the World Health Organization classification, the absence of EBV excludes the diagnosis of extranodal natural killer/T-cell lymphoma, nasal type. However, the association of EBV with this lymphoma in white patients is not clear. Therefore, absence of EBV alone does not necessarily exclude nasal-type natural killer/T-cell lymphoma, particularly because the histologic pattern in this case is highly characteristic of this tumor.     

Characterization of a novel T-cell lymphoma cell line established from a patient with systemic lupus erythematosus-associated lymphoma.

A malignant lymphoma developed in a 46-year-old male patient who had had systemic lupus erythematosus (SLE) for 18 years. The lymphoma was at disease stage IV at initial examination, and the patient died shortly thereafter. The lymphoma cells were cultured in vitro, and a continuous cell line, named SMZ-1, was established. The SMZ-1 cells, as well as the parental lymphoma cells, were of helper/inducer T-cell immunophenotype; they were positive for CD2, CD3, and CD4 antigens, and negative for CD8. Expression of CD5 and CD7 antigens was observed in a small percentage of the cells. The activation markers identified by antibodies against CD25, CD71, and HLA-DR antigens were positive. Cytogenetic analysis revealed that the SMZ-1 cells had a characteristic translocation between chromosomes 6 and 14 [t(6;14)(p21.1;q24)]. Southern blot analysis of DNA extracted from the cells demonstrated clonal rearrangement of the T cell receptor beta-chain gene. Integration of the human T-cell lymphotrophic virus type I (HTLV-I) genome was negative. The SMZ-1 cell lines should thus provide a useful model for characterization of peripheral T-cell lymphomas.     

Lineage determination of CD20- B-Cell neoplasms: an immunohistochemical study

We studied 61 CD20- B-cell lymphomas, including 29 cases of precursor B-cell lymphoblastic leukemia/lymphoblastic lymphoma (B-ALL/B-LBL), 25 cases of CD20- recurrent mature B-cell lymphoma after rituximab therapy, and 7 cases of CD20- diffuse large B cell lymphoma (DLBCL). We used markers specific for B lineage: CD79a, Pax-5, OCT.2, and BOB.1. All B-ALL/B-LBLs expressed Pax-5 (29/29 [100%]), 25 (93%) of 27 expressed BOB.1, 23 (79%) of 29 expressed CD79a, and 6 (22%) of 27 expressed OCT.2. The percentages of cases expressing Pax-5, CD79a, OCT.2, and BOB.1 in CD20- recurrent mature B-cell lymphomas after rituximab treatment were 88% (21/24), 84% (21/25), 81% (17/21), and 73% (16/22), respectively. CD20- DLBCLs rarely express routine B-lineage markers, such as and CD79a and Pax-5, but they expressed OCT.2 or BOB.1. Pax-5, BOB.1, and CD79a antigens are the most reliable B-lineage markers for paraffin immunophenotyping B-ALL/B-LBL. CD79a and Pax-5 should be used as the first-line B lineage-specific markers for rituximab-treated CD20- mature B-cell lymphomas. If negative, OCT.2 or BOB.1 may be useful. The newly identified B-lineage markers, OCT.2 and BOB.1, may be the most useful for the B-lineage determination of CD20- plasmablastic or primary effusion subtypes of DLBCL.     

Rare expression of T-cell markers in classical Hodgkin's lymphoma.

Hodgkin's and Reed-Sternberg cells of classical Hodgkin's lymphoma are primarily of B-cell origin, although there are instances of T-cell antigen expression suggesting T-cell origin. We comprehensively analyzed expression of various T-cell antigens in 259 classical Hodgkin's lymphoma cases using the tissue microarray technique. Expression of the T-cell antigens CD2, CD3, CD4, CD5, CD7 and CD8 was assessed by immunohistochemistry. Hodgkin's and Reed-Sternberg cells of T-cell marker-positive cases were microdissected and analyzed by a multiplex polymerase chain reaction for clonal immunoglobulin heavy chain- and T-cell receptor gamma gene rearrangements. In all, 12 cases (5%) expressed at least one T-cell marker in the following order: CD2 in 11 cases, CD4 in five, CD3 in two, and CD5 and CD8 in one case each; there were no CD7-positive cases, and five cases (2%) expressed more than one T-cell antigen. In positive cases, a mean fraction of 40% of the Hodgkin's and Reed-Sternberg cells (range 20-100%) expressed the analyzed T-cell markers. Two cases (<1%) evidenced clonal T-cell receptor gamma gene rearrangement. Phenotypic expression of T-cell antigens in Hodgkin's and Reed-Sternberg cells of classical Hodgkin's lymphoma is rare (5%), while genotypically, less than 1% of classical Hodgkin's lymphomas are of possible T-cell origin. Therefore, T-cell antigen expression on Hodgkin's and Reed-Sternberg cells is aberrant in the majority of cases and only infrequently classical Hodgkin's lymphomas are of T-cell origin.     

胃T细胞淋巴瘤临床病理观察

目的 探讨胃T细胞淋巴瘤的临床病理学特点.方法 收集7例胃T细胞淋巴瘤病例标本,对其进行了临床病理分析、免疫组织化学检测、EBER原位杂交检测及T细胞受体(TCR)基因重排检测.结果 7例病例中6例为男性,1例为女性,平均发病年龄为45岁.6例可获得资料的病例中,1例有长期腹泻史,5例有低蛋白血症.组织学上,7例标本中,有5例表现为肿瘤细胞体积较大而不一致,2例表现为大小一致的中等细胞.1例病例可见肿瘤细胞浸润腺上皮.所有病例的肿瘤组织均不表达CD20及CD79a.7例病例中,各有6例表达CD3及T细胞胞质内抗原,各有4例表达CD5、βF-1及CD30,有3例表达CDM,各有1例病例表达CD8、CD56、问变性淋巴瘤激酶及粒酶B.7例病例肿瘤细胞EBER原位杂交检测均为阴性且都存在TCR基因克隆性重排.结论 胃T细胞淋巴瘤是一种少见的恶性淋巴瘤,具有独特的临床病理特点.     

CD5+ follicular lymphoma: a clinicopathologic study of three cases

Follicular lymphoma (FL) is a low-grade lymphoma that typically lacks CD5 antigen expression. We report 3 cases of FL with unusual expression of CD5. All cases showed histologic features of FL, including effaced nodal architecture, follicular growth pattern, and a spectrum of grades from 1 to 3 using World Health Organization criteria. In flow cytometric studies, all 3 cases showed a light chain-restricted, CD19+, CD20+ B-cell population coexpressing CD10 and low-level CD5. Immunohistochemical studies demonstrated an identical B-cell immunophenotype with weak expression of CD5 and coexpression of bcl-2 protein and the germinal center-associated markers, CD10 and bcl-6 protein. None of the cases showed expression of CD43, cyclin D1, or IgD. By molecular analysis, immunoglobulin heavy chain gene rearrangements were demonstrated in all 3 cases, and 2 of 3 cases had a t(14;18). These cases highlight the difficulty classifying these lymphomas by flow cytometric studies alone and emphasize the importance of recognizing FL in the differential diagnosis of CD5+ B-cell lymphomas.     

Differentiating lymphoblastic lymphoma and Ewing's sarcoma: lymphocyte markers and gene rearrangement.

We encountered a child with an intraosseous small round cell tumor that was negative for LCA, CD20 (L26), and CD3 and positive for vimentin, CD99 (MIC-2), and periodic acid-Schiff. The tumor exhibited rosette-like formations. This case was initially interpreted as Ewing's sarcoma (ES); however, additional studies revealed positivity for CD79a, CD43, and TdT expression, and an immunoglobulin heavy chain gene rearrangement (IgH-R) by polymerase chain reaction (PCR) established this to be a precursor B-lymphoblastic lymphoma. Because the differential diagnosis of ES and lymphoblastic lymphoma can be difficult and the differential diagnostic value of leukocyte antigens and immunoglobulin heavy chain gene rearrangement studies have not been fully evaluated, we conducted a more extensive investigation on 33 (21 soft tissue and 12 intraosseous) ES cases. Cases were retrieved from the files of the Department of Pathology at Georgetown University and from the Soft Tissue Registry of the Armed Forces Institute of Pathology. The cases were studied by light microscopy, immunohistochemistry, and PCR for IgH-R and T cell receptor gamma chain gene rearrangement (Tgamma-R). There were 17 females and 16 males; the mean age was 29.3 years. Locations included the extremities (n = 17) and trunk (n = 16). All cases fit the ES spectrum by light microscopy and immunohistochemistry, as previously determined, and were negative for lymphoid markers (LCA, CD3, CD20, CD43, CD79a, and TdT), CD10 and CD34. CD99 was positive in 31/33 and bcl-2 was weakly positive in 13/33 cases. All 21 cases studied for gene rearrangements by PCR were negative for IgH-R and Tgamma-R. Distinction of intraosseous lymphoblastic lymphoma from ES may be difficult because lymphomas may occasionally exhibit unexpected morphologic and immunophenotypic properties including LCA, CD3 and CD20 negativity and cytokeratin positivity. Additional analysis using CD79a, CD43, TdT, and PCR should be performed to avoid misdiagnosis. True ES is negative for lymphoid markers including CD79a, CD43, and TdT, as well as for IgH-R and Tgamma-R.     

Primary CD20+CD10+CD8+ T-cell lymphoma of the skin with IgH and TCR beta gene rearrangement

Most cutaneous T-cell lymphomas are derived from mature postthymic T cells of the CD4 subtype. When other less common profiles are encountered, a diagnostic challenge is posed. Accurate categorization is critical because of the specificity of therapeutic regimens, including biologics. A 65-year-old woman was seen in 2001 because of a thigh mass manifesting an unusual phenotype eventually categorized as a mature postthymic CD8+ T-cell lymphoma with CD10 and weak CD20 expression. Molecular studies revealed T-cell receptor and heavy chain immunoglobulin rearrangement. Her cutaneous disease progressed despite several cycles of chemotherapy and radiation therapy. However, a therapeutic trial with denileukin diftitox resulted in a striking response. The importance of this case lies in the novel phenotype and dual T- and B-cell rearrangements. Rather than representing an aberrant phenotype, this tumor may represent the malignant counterpart of a benign population of weakly CD20+ T cells of the CD8 subset.