Terminal deoxynucleotidyl transferase-positive lymphoid cells in reactive lymph nodes from children with malignant tumors: incidence, distribution pattern, and immunophenotype in 26 patients

Indolent B-Lineage Precursor Populations Identified by Flow Cytometry and Immunohistochemistry in Benign Lymph Nodes

OBJECTIVES

In this retrospective study, we report a series of benign lymph nodes showing small populations of normal B-cell precursors characterized by flow cytometry and immunohistochemistry.

METHODS

Ten cases identified during clinical flow cytometry practice were retrospectively reanalyzed with particular attention to hematogone categorization and enumeration. Immunohistochemical staining was performed on five excisional lymph node biopsy specimens to characterize the morphologic correlate.

RESULTS

Populations of hematogones ranging from 0.13% to 1.86% (median, 0.51%) of all viable leukocytes were demonstrated in 10 benign lymph node samples from eight different patients ranging in age from 17 to 45 years (median, 37.5). These hematogones showed a characteristic immunophenotype (CD19+/CD10+) and maturational pattern by flow cytometry, with progression from stage 1 (median, 0.03%) to stage 2 (median, 0.19%) to stage 3 (median, 0.26%) seen in all cases. Immunohistochemical staining on five excisional biopsy specimens demonstrated a distinct perisinusoidal distribution of CD10+/CD20+ cells with a subset of TdT+ cells, providing a morphologic correlate.

CONCLUSIONS

To our knowledge, this is the first study to characterize distinct hematogone populations within benign lymph nodes by both flow cytometry and immunohistochemistry. Recognizing these normal B-cell precursor populations is important to avoid their miscategorization as a CD10+ B-cell neoplasm.

Terminal Deoxynucleotidyl Transferase Commonly Expresses in Germ Cell Tumors: Evaluation on a Large Series from Multiple Centers

Aim

The concrete features of expression of terminal deoxynucleotidyl transferase (TdT) are needed to be revealed in male and female germ cell tumors (GCTs).

Methods

TdT immunostaining was performed in 195 GCTs, and the tumor and/or tumorous components included seminomas, germ cell neoplasias in situ (GCNISs), dysgerminomas, embryonal carcinomas (ECs), extragonadal germinomas, yolk sac tumors (YSTs), teratomas, and spermatocytic tumors. Twenty-one sex cord-stromal tumors were also added. Expression of the classical germ cell tumor markers (PLAP, OCT4, SALL4, CD117, and D2-40) was compared to that of TDT.

Results

Nearly all (tumors or tumorous components) seminomas (99%, 107/108), GCNISs (98%, 51/52), dysgerminomas (94%, 17/18), ECs (100%, 15/15), and extragonadal germinomas (100%, 11/11) were positive for TdT. None of the cells in YSTs (0/38), teratomas (0/19), spermatocytic tumors (0/1), or sex cord-stromal tumors (0/21) were immunoreactive for TdT staining. The normal testicular and ovarian gonadal tissues were also negative for TdT. However, TdT presented with significant loss of antigen immunoreactivity in the paraffin-embedded tissues older than 3 years, giving rise to weak or moderate staining in a subset of cases. The expressions of TdT showed no significances with PLAP, OCT4, SALL4, CD117, and D2-40 during the diagnosis of the most GCTs (P>0.05), except for with PLAP, SALL4, or CD117 in YST (P=0.000 each), and D117 (P=0.000) or D2-40 (P=0.006) in ECs.

Conclusion

Our findings further verify that TdT can serve as a new GCT marker for seminomas, GCNISs, dysgerminomas, ECs, and extragonadal germinomas, with a highly positive rate. Awareness of TdT positivity in GCTs contributes to the prevention of erroneous diagnoses, particularly in the setting of core needle biopsies. To determine the properties where TdT staining may not be apparent in some old archived paraffin-embedded tissues, one could circumvent the potential misinterpretations of false-negative immunohistochemistry results.

Terminal deoxynucleotidyl transferase (TdT) expression is associated with FLT3-ITD mutations in Acute Myeloid Leukemia

The terminal deoxynucleotidyl transferase (TdT) is a DNA polymerase expressed in acute myeloid leukemias (AMLs), where it may be involved in the generation of NPM1 and FLT3-ITD mutations. We studied the correlations between TdT expression and FLT3-ITD or NPM1 mutations in primary AML samples, and the impact on patients' survival. TdT expression was analyzed in 143 adult AML patients by flow cytometry as percentage of positivity and mean fluorescence intensity (MFI) on blasts. TdT was positive in 49 samples (34.2%), with a median of 48% TdT-positivity (range 7-98) and a median MFI of 2.70 (range 1.23-30.54). FLT3-ITD and NPM1 mutations were present in 24 (16.7%) and 34 (23.7%) cases, respectively. Median TdT expression on blasts was significantly higher in FLT3-ITD+, as compared with FLT3-ITD- AMLs (median 8% vs 0% respectively, p = 0.035). NPM1 mutational status, FLT3-ITD allelic ratio, karyotype, and ELN risk groups, did not correlate with TdT expression or MFI on blasts. TdT + patients had poorer survival as compared to TdT-, but this result was not confirmed by the multivariable analysis, where ELN risk stratification as well as age and type of treatment remained independent prognostic factors for OS. In summary, our results support the possible implication of TdT enzyme in the generation of FLT3-ITD mutations in AML.

High-grade B-cell lymphomas with TdT expression: a diagnostic and classification dilemma

Mature B-cell neoplasms and immature or precursor B-cell neoplasms need to be distinguished because these patients usually require different therapeutic approaches. B-cell neoplasms that express TdT without unequivocal other features of immaturity may therefore present a diagnostic challenge. We describe 13 patients with TdT-positive aggressive B-cell lymphoma. The clinicopathologic features of these patients were highly heterogeneous, but for the purpose of this study we grouped these cases as follows: (1) de novo high-grade B-cell lymphoma with MYC, BCL2, and/or BCL6 rearrangements (double-hit or triple-hit lymphoma) with TdT expression. In this group we included two cases of de novo composite lymphoma in which there were components of diffuse large B-cell lymphoma and TdT-positive blastic B-cell lymphoma; (2) TdT-positive aggressive B-cell lymphoma arising in patients who previously had follicular lymphoma; (3) initial relapse of TdT-negative aggressive B-cell lymphoma in patients who previously had follicular lymphoma, followed by relapses in which the neoplasm acquired TdT expression; and (4) mature B-cell lymphomas that acquired TdT expression at relapse. This group included one case of EBV-positive diffuse large B-cell lymphoma and one case of pleomorphic variant mantle cell lymphoma. All patients in this study had an aggressive clinical course and a dismal outcome despite appropriate therapy. Rather than "squeezing" these cases into current World Health Organization classification categories, we suggest the use of a descriptive term such as high-grade B-cell lymphoma with TdT expression. In these tumors, the cytogenetic findings and poor prognosis of this patient subgroup suggest that these neoplasms need to be distinguished from B-lymphoblastic leukemia/lymphoma. Segregation of these neoplasms also may foster additional research on these neoplasms.

Benign TdT-positive cells in pediatric and adult lymph nodes: a potential diagnostic pitfall

Benign terminal deoxynucleotidyl transferase (TdT)-positive cells have been documented in a variety of nonhematopoietic tissues. Scant data are, however, available on their presence in nonneoplastic lymph nodes. This study is aimed to (1) characterize the presence/distribution of benign TdT-positive cells in pediatric and adult reactive lymph nodes and (2) define the phenotype and nature of such elements. This retrospective study considered 141 reactive lymph nodes from pediatric and adult patients without history of neoplastic disease. TdT-positive cells were characterized by immunohistochemical and morphometric analyses, and their presence was correlated with the clinical-pathological features. The nature of TdT-positive cells was investigated by (1) double immunostaining for early lymphoid cell markers and (2) assessment of TdT expression in fetal lymph nodes. Sparse TdT-positive cells were documented in all pediatric cases and in most (76%) adult lymph nodes. TdT-positive cell density was higher in children than adults (15.9/mm² versus 8.6/mm²; P < .05). TdT positivity did not correlate with any clinical or histological parameter, and double immunostaining disclosed a phenotype compatible with early lymphoid precursors (positivity for CD34 and CD10, and variable expression of CD7). A very high TdT-positive cell density (802.4/mm²) was reported in all fetal lymph nodes. In conclusion, TdT-positive cells are a common finding in pediatric and adult lymph nodes. The interstitial distribution and low number of such cells allow for the differential diagnosis with precursor lymphoid neoplasms. The high density in fetal lymph nodes and the phenotype of such cells suggest their belonging to an immature lymphoid subset gradually decreasing with age.

Terminal Deoxynucleotidyl Transferase (TdT)-negative Lymphoblastic Leukemia in Pediatric Patients: Incidence and Clinical Significance

Pediatric terminal deoxynucleotidyl tranferase (TdT)-negative precursor B- or T-lymphoblastic leukemia/lymphoma (B-LL and T-LL) cases are rare and their prognostic significance remains controversial. We aimed to determine the frequency of TdT-negative B- and T-LL in the community hospital setting. Between 2005 and 2015, 43 pediatric patients were diagnosed with lymphoblastic leukemia at our institution, of which 6 (14%) were characterized as TdT-negative by flow cytometric analysis. Four of these 6 patients had B-LL and the other 2 had T-LL. Two of the 6 TdT-negative patients also had undetectable CD34 expression by flow cytometry (TdT/CD34 double-negatives). Subsequent paraffin immunohistochemistry confirmed the negative CD34 expression in both cases. By contrast, all the 6 patients had weak TdT-like immunoreactivity in their marrow despite the negative flow cytometric analysis. Furthermore, neither TdT/CD34-negative cases showed myc rearrangement by fluorescent in situ hybridization, ruling out Burkitt leukemia as a differential diagnostic consideration. We conclude that TdT-negative pediatric B- and T-LL cases (especially those that are TdT/CD34 double-negative) may pose diagnostic challenge to hematopathologists, and ancillary studies (paraffin immunohistochemistry to detect TdT and fluorescent in situ hybridization to exclude myc rearrangement) may be instrumental in reaching the correct diagnosis.

Immature Terminal Deoxynucleotidyl Transferase Positive B Cells are Detected in a Subset of Adult and Pediatric Liver Biopsies

Terminal deoxynucleotidyl transferase (TdT) is a nuclear enzyme restricted to precursor lymphoid cells and their malignant counterparts; immunohistochemical TdT labeling is helpful in recognition of lymphoblasts, which can resemble mature lymphocytes. The diagnosis of B-lymphoblastic leukemia/lymphoma (B-ALL) is occasionally first encountered on liver core biopsy, but TdT immunostain specificity for B-ALL is not clearly established in this setting, which can be problematic when only a few TdT-positive cells are identified. In this study, we evaluated the incidence and distribution of immature B lymphocytes coexpressing TdT and PAX-5, in pediatric and adult liver biopsies, to determine whether a normal complement of hepatic immature B cells can be detected, which must be recognized in a workup to exclude B-ALL. We selected 41 pediatric and adult liver biopsies with a significant portal and/or sinusoidal hematolymphoid infiltrate and performed immunohistochemical stains for TdT and PAX-5 to identify and categorize distribution of immature B cells. TdT-positive cells were detected in 40% of pediatric liver biopsies with a significant hematolymphoid infiltrate (4/10), which included all biopsies from neonates (and infants under 9 wk of age). In adults, immature B-cell infiltrates were less common (6%, 2/31). Dual immunostaining was performed on 2 cases of neonatal hepatitis, which documented B-cell lineage in at least a subset of TdT-positive cells and there was no colabeling with CD3. Immature B cells can be detected in liver biopsies in a variety of clinical settings, most commonly in children, and presence of a few TdT-positive cells cannot be considered entirely specific for involvement by B-ALL. Further workup for B-ALL can be warranted if there is more extensive multifocal portal and/or sinusoidal involvement by blasts with TdT labeling.

Flow Cytometry in Pediatric Hematopoietic Malignancies

Utility of flow cytometry in the evaluation of pediatric hematopoietic neoplasms and the differences from adult hematopoietic neoplasms are discussed in this review. Distinction of hematogones from B-lymphoblasts, detection of residual/relapsed disease after novel targeted therapies, and evaluation of pediatric myeloid neoplasms are discussed.

TdT-positive Infiltrate in Inflamed Pediatric Kidney: A Potential Diagnostic Pitfall

We encountered a patient with infantile nephrotic syndrome associated with a dense interstitial inflammatory infiltrate and prominent extramedullary hematopoiesis. Immunohistochemical analysis revealed numerous terminal deoxynucleotidyl transferase (TdT)-positive cells, which may raise concern for lymphoblastic lymphoma. Thus, we further characterized a group of pediatric kidneys with inflammation. TdT-positive nuclei were quantitated, and dual immunostains for TdT/CD79a, TdT/CD3, and TdT/CD43 were performed in a subset of cases; flow cytometry was performed in 1 case. TdT-positive nuclei were present in inflamed pediatric kidneys in 40 of 42 patients. TdT counts (average of 3 maximal high-power fields) ranged from 1 to >200, with a mean of 47. The presence and number of TdT-positive nuclei showed a strong association with younger patient age. Extramedullary hematopoiesis was identified in 11/42 patients, all under the age of 1. The presence of extramedullary hematopoiesis did not correlate with TdT count (P=0.158). Dual immunostaining and flow cytometric analysis in 1 case showed weak expression of B-cell markers and favored normal precursor B cells. Although TdT is a common marker of lymphoblastic lymphoma, we have demonstrated that TdT-positive cells may be part of the inflammatory milieu in infant kidneys. Together with cytologic, architectural, and clinical features, these data can help to avoid misinterpretation of involvement by lymphoblastic lymphoma/leukemia.

The pattern of gene expression and gene dose profiles of 6-Mercaptopurine- and 6-Thioguanine-resistant human leukemia cells

Exposure of MOLT4 human T-cell leukemia cells to 6-Mercaptopurine (6-MP) and 6-Thioguanine (6-TG) resulted in acquired resistance associated with attenuated expression of the genes encoding concentrative nucleoside transporter 3 (CNT3) and equilibrative nucleoside transporter 2 (ENT2). To identify other alterations at the RNA and DNA levels associated with 6-MP- and 6-TG resistance, we compared here the patterns of gene expression and DNA copy number profiles of resistant sublines to those of the parental wild-type cells. The mRNA levels for two nucleoside transporters were down-regulated in both of the thiopurine-resistant sublines. Moreover, both of these cell lines expressed genes encoding the enzymes of purine nucleotide composition and synthesis, including adenylate kinase 3-like 1 and guanosine monophosphate synthetase at significantly lower levels than wild-type cells. In addition, expression of the mRNA for a specialized DNA polymerase, human terminal transferase encoded by the terminal deoxynucleotidyl transferase (DNTT) gene, was 122- and 93-fold higher in 6-TG- and 6-MP-resistant cells, respectively. The varying responses to 6-MP- and 6-TG observed here may help identify novel cellular targets and modalities of resistance to thiopurines, as well as indicating new potential approaches to individualization therapy with these drugs.

Expression of JL1 is an effective adjunctive marker of leukemia cutis

CONTEXT

Specific differentiation of leukemia cutis (LC) from nonleukemic dermatoses is crucial to ensure proper treatment for the disease. Because of the exceptionally variable histologic features of LC and the frequent nonleukemic dermatoses in leukemia patients, identification of leukemic cells that infiltrate skin lesions is important. Here, we introduce JL1, a novel leukemia-associated surface antigen, which is not expressed in mature human tissue but in cortical thymocytes and small subpopulations of bone marrow hematopoietic precursors.

OBJECTIVES

To assess the expression pattern of JL1 in LC and compare it with other commonly used markers. Also, to evaluate the expression of JL1 in other cutaneous lesions that need differential diagnoses.

DESIGN

Immunohistochemical staining with anti-JL1 and other commonly used markers for LC was performed on paraffin-embedded skin biopsies from 32 cases of LC with acute lymphoblastic leukemia/lymphoma and acute myelogenous leukemia. Immunohistochemical staining score was evaluated in each case according to the proportion of positive tumor cells found. JL1 staining was also done on 96 reactive or neoplastic cutaneous lesions.

RESULTS

JL1 was detected in 7 of 11 acute lymphoblastic leukemia/lymphoma LC (63.6%) and 7 of 21 acute myelogenous leukemia LC (33.3%), with invariably high-staining scores. None of the other cutaneous lesions or normal tissues expressed JL1. The expression pattern of JL1 was not altered in 2 patients with follow-up biopsies.

CONCLUSIONS

Our finding that JL1 is expressed exclusively and stably by leukemic cells suggests that it can be used as a useful adjunctive marker for initial diagnosis and follow-up biopsy of LC, particularly in cases of scarce infiltrates.

Leukemic involvement is a common feature in mantle cell lymphoma

BACKGROUND

The reported incidence of peripheral blood involvement in patients with mantle cell lymphoma (MCL) ranges from 13% to 77%. The aim of the study was to analyze the prevalence and the biologic and clinical significance of leukemic involvement in a series of patients with MCL.

METHODS

Leukemic expression was assessed by conventional morphology and flow cytometry (FC) in 48 patients. In addition, comparative genomic hybridization (CGH) was performed in 27 patients.

RESULTS

At diagnosis, 44 patients (92%) had evidence of leukemic expression by FC, including 8 patients (17%) without morphologically apparent leukemic involvement. Moreover, a lymphocyte count > or =5 x 10(9)/L was observed in 25 cases (52%). The most frequent imbalances detected by CGH were gains of 3q, 7p, 8q, 9q, 12q, and 13q, and losses of 13q, 1p, 9p, 11q, 10p, 17p, 6q, 8p, and 9q. Using a cutoff of 5 x 10(9)/L lymphocytes, cases with lymphocytosis more frequently presented with gains of 3q (P = .02), losses of 10p (P = .05), a low response rate (P = .04), and a short survival (P = .05).

CONCLUSIONS

Leukemic expression at diagnosis detected by FC was found to be highly frequent in this series of patients with MCL. Although morphologically apparent leukemic expression was not associated with specific chromosomal alterations detected by CGH, a lymphocyte count > or =5 x 10(9)/L was correlated with particular genetic abnormalities and a poor outcome.