You are here

  • Home
  • Archive
  • Volume 71, Issue 4
  • Comparison of karyotyping, TCL1 fluorescence in situ hybridisation and TCL1 immunohistochemistry in T cell prolymphocytic leukaemia

Article Text

Article menu

Download PDFPDF

Original article
Comparison of karyotyping, TCL1 fluorescence in situ hybridisation and TCL1 immunohistochemistry in T cell prolymphocytic leukaemia
  1. Yi Sun1,2,
  2. Guilin Tang1,
  3. Zhihong Hu1,
  4. Beenu Thakral1,
  5. Roberto N Miranda1,
  6. L Jeffrey Medeiros1,
  7. Sa A Wang1
  1. 1 Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
  2. 2 Department of Pathology, The Second Xiangya Hospital of Central South University, Changsha, Hunan Province, China
  1. Correspondence to Dr Sa A Wang, Department of Hematopathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA; swang5{at}mdanderson.org

Abstract

Aims T cell prolymphocytic leukaemia (T-PLL) is defined as an aggressive T cell leukaemia composed of small to medium-sized lymphocytes with a mature T cell immunophenotype. Most of these cases are known to be associated with inv(14q11q32)/t(14;14)(q11;q32) or rarely t(X;14)(q28;q11). However, T-PLL can show variations in clinical presentation, morphology or immunophenotype that can make a diagnosis of T-PLL challenging. We aim to explore the value of ancillary testing in the diagnosis of T-PLL.

Methods With this large cohort of 69 patients with T-PLL, we compared the diagnostic utility of conventional cytogenetics, TCL1 rearrangement by fluorescence in situ hybridisation (FISH) and TCL1 expression by immunohistochemistry (IHC).

Results Conventional karyotyping was performed in all 69 patients and was abnormal in 44 (65%), showing 14q32 abnormalities in 31 (43%) and t(X;14) (MTCP) in 2 (3%). TCL1 rearrangement was assessed by FISH in 26 cases and was positive in 23 (85%). All cases with 14q32 abnormalities shown by karyotype were positive for TCL1 rearrangement by FISH, whereas 12/15 (80%) cases without 14q32 abnormalities were also positive. TCL1 overexpression by IHC was detected in 51/64 (81%), including 40/42 (95%) cases with TCL1/14q32 rearrangement, and 3 cases without, showing a concordance of 89%. TCL1 IHC was negative in both cases with t(X;14)(q28;q11).

Conclusions Our study shows that TCL1 by IHC is a convenient test, positive in >80% T-PLL. Conventional cytogenetics is insensitive in the detection of 14q32/TCL1 rearrangements but provides more complete information of the chromosomal landscape of T-PLL. FISH for TCL1 rearrangement is very valuable in diagnostic challenging cases.

  • Haematology
  • Leukaemia
  • Fish
  • Immunohistochemistry

https://doi.org/10.1136/jclinpath-2017-204616

Statistics from Altmetric.com

    Request Permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

    Introduction

    T cell prolymphocytic leukaemia (T-PLL) is defined in the WHO classification as an ‘aggressive T cell leukaemia characterized by the proliferation of small to medium-sized prolymphocytes with a mature or post-thymic T cell phenotype involving peripheral blood (PB), bone marrow (BM), lymph nodes, liver, spleen and skin’.1 The diagnosis of T-PLL is usually established based on a combination of clinical presentation, morphology and immunophenotype. However, variations in morphology2 and immunophenotype3 have been observed in T-PLL cases. In addition, although T-PLL is generally an aggressive Tcell leukaemia, some patients may present with an indolent clinical course.4 5 The clinicopathological heterogeneity indicates the need for better disease-defining markers in the diagnosis of T-PLL. Lastly the role of genetic studies in establishing the diagnosis of T-PLL is not uniform.

    TCL1 overexpression, usually assessed by immunohistochemistry (IHC) or western blot, is reported in 70%–80% of T-PLL cases.6 TCL1 expression occurs most often as a result of inv(14)(q11q32) of t(14;14)(q11;q32) juxtaposing the TRA at 14q11 with the oncogene TCL1 at 14q32.1.7 It has been shown that TCL1 translocations are specific to T-PLL and are not seen in other mature T cell neoplasms.8 9 It is also reported that TCL1 can be activated by hypomethylation of the TCL1 promoter region.10 Another recurrent cytogenetic abnormality reported in T-PLL is t(X;14)(q28;q11), involving TCRA and MTCP1 at Xq28.11 TCL1 and MTCP1 are thought to play essential roles in the pathogenesis of T-PLL, as their overexpression leads to activation of protein kinase B (Akt)12 13 and impairment of protein kinase C (PKC) theta and extracellular signal-regulated kinase (ERK) pathways,14 resulting in enhanced cell proliferation. A comparison of TCL1 expression by IHC, TCL1 rearrangement by fluorescence in situ hybridisation (FISH) and conventional cytogenetics in establishing the diagnosis of T-PLL has not been systemically studied.

    In this study, we collected a large series of T-PLL cases and assessed the diagnostic utility of conventional cytogenetics, FISH, as well as flow cytometry immunophenotype (FCI) and IHC assessment of TCL1 in the diagnosis of T-PLL.

    Materials and methods

    Patients

    We searched the pathology archives of our hospital over a 10-year period (January 2006 through December 2016) for patients presenting with a mature T cell leukaemia diagnosed either as T-PLL initially or as a leukaemic T cell neoplasm with a major differential diagnosis of T-PLL. These cases were reviewed retrospectively in conjunction with ancillary testing data. A subset of cases were excluded as they better fitted other diagnoses such as adult T cell leukaemia/lymphoma because of human T-lymphotropic virus 1 (HTLV-1)-positive serology, Sézary syndrome because of erythroderma or a history of mycosis fungoides, or peripheral T cell lymphoma (PTCL) with a leukaemic presentation when disease initially manifested with peripheral lymphadenopathy or extranodal involvement. Of the final included cases, T-PLL was a diagnosis of exclusion for cases presenting as a leukaemic mature T cell neoplasm that did not belong to any of other entities in the WHO classifications1. The demographic information, clinical presentation, laboratory data, treatment and clinical follow-up information were collected. The study was approved by the internal review board of our hospital.

    Morphological assessment and IHC

    We reviewed the peripheral blood (PB) smears, bone marrow (BM) biopsy and aspirate smears, as well as any available lymph node or extranodal tissue biopsies. BM was evaluated for cellularity, infiltrative pattern and morphological characteristics including leukaemic cell size, presence of nucleoli and nuclear shape.

    IHC studies were performed using formalin-fixed, paraffin-embedded BM core biopsy or aspirate clot specimens and the method that was fully validated in our clinical laboratory. Mouse anti-TCL1 antibodies (1:500, clone eBio1-21; eBioscience) and mouse anti-CD3 antibodies (1:25, clone F7.2.38; DAKO Cytomation, Glostrup, Denmark) were performed in parallel in all cases. TCL1 expression was assessed on CD3+ T cells, scored as positive, subset (if <30% of tumour cells), or negative. In cases with a less infiltrate (<20%) and subset of TCL1 staining, the TCL1 positivity was confirmed not in B cells by CD20 IHC stain.

    Flow cytometry immunophenotyping

    Samples for FCI, either BM, PB or both, were studied at the time of diagnosis, using four-colour (years 2006–2009) or eight-colour multicolour flow cytometry methods (years 2009–2016) (FACSCanto II instruments, BD Biosciences). A panel of antibodies for T cell neoplasms work-up was performed, including CD2, CD3, CD4, CD5, CD7, CD8, CD25, CD26, CD45, CD52, CD56, CD57, TCRαβ and TCR γδ, using a method similar to what we described previously.15

    Cytogenetic studies

    Conventional chromosomal analysis was performed on G-banded metaphase cells prepared from unstimulated 24-hour and phytohaemagglutinin-stimulated 72-hour BM aspirate cultures using methods described previously. Twenty metaphases were analysed and the results were reported using the International System for Human Cytogenetic Nomenclature (ISCN 2013).16 All karyotyping was performed at our hospital.

    FISH for TCL1 using a dual-colour,8 9 breakapart probe (Cytocell, New York, USA) was performed on freshly harvested BM cultured cells (metaphase or interphase) or paraffin-embedded BM aspirate clot (non-decalcified) tissue sections in a subset of cases.

    Results

    Patients

    The study group included 69 patients who met the criteria for the diagnosis of T-PLL. The demographic data, clinicopathological findings and laboratory data are summarised in table 1. In brief, this cohort included 45 men and 24 women with a median age of 65 years (36–86). Splenomegaly and/or hepatomegaly was present in 32/69 (46%) and lymphadenopathy in 35/69 (51%) patients.

    View this table:
    Table 1

    Clinical, laboratory and BM features of 69 patients with T cell prolymphocytic leukaemia

    The median white blood cell count (WBC) was 45.0×109/L (range 12.3–733×109/L) with a median absolute lymphocyte count of 35.8×109/L (12.3–733). Serum lactate dehydrogenase (LDH) level was elevated in 38/63 (60%) patients with a median of 722 U/L (range 141–13,373; normal 313–618).

    Morphological and flow cytometry immunophenotypical features

    All patients had BM infiltration by T-PLL, and the lymphocytes represented a median of 50% (range 5–90) of the BM cellular elements. The infiltrative pattern was predominantly interstitial, with some cases also showing focal or diffuse areas (58/67 patients, 87%). In 8/67 (11%) patients, lymphoid nodules and aggregates were observed along with an interstitial infiltrative pattern. In one patient, the infiltrate was only as aggregates. Cytologically, 47/68 (69%) patients showed typical small to medium-sized cells, each with a single conspicuous nucleolus; 3 (4%) patients had medium to large-sized cells with nucleoli, and 18/68 (26%) patients small to medium-sized cells with only occasional or no nucleoli; some cases in the latter group had very irregular or cerebriform nuclei contours (figure 1). The latter group with atypical morphological features might be considered as small cell variant or Sézary syndrome-like forms.

    Figure 1
    Figure 1

    Variations in tumour cell morphology observed in T cell prolymphocytic leukaemia (T-PLL). (A) Typical T-PLL cells, small to medium with small but conspicuous nucleoli, cytoplasmic blebs; (B) ‘small cell variant’ T-PLL, cells with clumping chromatin, cells with no visible nucleoli; (C) some cells have very irregular nuclear contours (cerebriform, Sézary-like). Wright-Giemsa, original magnification ×1000.

    The T-PLL cells were CD4+/CD8− in 48/68 (70%) patients, CD8+/CD4− in 1/68 (2%) and CD4+/CD8+ in 19/68 (28%) patients. In the latter group, four patients showed uniform CD4 expression with partial/subset CD8 expression, and three patients showed uniform CD8+ with partial/subset CD4 expression. CD7 was brightly positive in 63/68 (93%) patients and dimly or partially positive in 5/68 (7%) patients. Loss of surface CD3 was observed in 6/68 (9%) patients. CD26 was assessed in 64 patients and uniformly positive (in >90% positive cells) in 49 (76%), partial or dim in 5 (8%) and negative in 10 (16%). All cases were positive for CD2 and CD5, although some variations in the levels of expression (often brighter) were observed.

    Karyotype, TCL1 arrangement by FISH and TCL1 IHC

    Karyotypic data were available in all patients. Twenty-five (36%) patients had an essentially normal karyotype, including 22 without abnormalities and 3 men who had –Y as the sole abnormality. The BM specimens and harvested cells were considered adequate for cytogenetic testing. The remaining 44 (65%) patients had an abnormal karyotype, including 43 with a complex karyotype and 1 with a non-complex karyotype. Inv(14)(q11.2q32) was identified in 27 (39%) patients and representing 61% of all patients with an abnormal karyotype. Other abnormalities involving 14q32 were seen in another three patients, all having add(14)(q32), and one also der(8)t(8;14)(p22;q32). t(X;14)(q28;q11.2) was detected in two patients. i(8)(q10) was present in 21 of 44 (48%) patients with an abnormal karyotype, and 6 (9%) of these patients had no evidence of inv(14)(q11.2q32), +14q32 or t(X;14)(q28;q11.2). Other abnormalities identified in these T-PLL cases included −6q, −11q, −13q, −17 p, −12 p, less commonly −5/5q-, or −7/7q- or 20q-.

    TCL1 FISH was performed in 26 cases, all on BM samples. In total, FISH was positive for TCL1 rearrangement in 23/26 (89%) patients (figure 2), including two patients in whom only a subset of tumour cells (~10% of total nucleated cells and ~20% of estimated tumour cells) were positive.

    Figure 2
    Figure 2

    Fluorescence in situ hybridisation analysis using a TCL1 dual-colour, breakapart probe (Cytocell) on a previously G-banded metaphase. A split signal (one red, one green) is observed on the derivative chromosome 14 with inv(14)(q11q32) (inserted) indicating TCL1 rearrangement.

    TCL1 expression assessed by IHC was performed in 64 patients. TCL1 was positive in 51/64 (81%) patients. TCL1 expression in T-PLL cells was uniform in 46 (90%) patients and present in a subset (<30%) of leukaemic cells in five patients (10%) (figure 3). In the latter, the median was about 20% (10%–29%). In these cases, we also performed CD3 IHC, and assessed the expression of TCL1 in T-PLL specifically.

    Figure 3
    Figure 3

    TCL1 expression by immunohistochemistry. BM (A and B, H&E) show an interstitial/diffuse leukaemic infiltrative pattern. (A) T-PLL cells are often small; (B) T-PLL cells in this case are medium to slightly large. Both cases are strongly positive for CD3. TCL1 immunohistochemistry in case (A) shows a uniform expression and (B) shows TCL1 reactivity only in a small subset of T-PLL cells. This immunohistochemistry result is equivocal that is difficult to interpret; however, fluorescence in situ hybridisation confirmed the presence of TCL1 rearrangement. Original magnification: ×400. T-PLL, T cell prolymphocytic leukaemia.

    Correlations between karyotype, TCL1 rearrangement by FISH and TCL1 by IHC

    We categorised the karyotypic data as follows: (1). normal/−Y; (2) abnormal with inv(14); (3) abnormal with other 14q32 abnormality; (4) t(X;14); and (5) abnormal but without 14q32 or t(X;14) abnormalities. The correlation of these five subgroups with TCL1 IHC and TCL1 FISH is shown in table 2. In brief, in patients with an abnormal karyotyping containing inv(14), TCL1 was rearranged by FISH in all cases (11/11; 100%), and TCL1 expression by IHC was detected in all but one case (22/23; 96%). In three patients with add(14)(q32) abnormalities other than inv(14), TCL1 aberrancy was confirmed in all three patients, either by TCL1 rearrangement by FISH (2/2) or TCL1 overexpression by IHC (2/2). In two patients with t(X;14)(q28;q11) presumably involving MTCP, TCL1 expression by IHC was completely negative. In patients with a normal karyotype, TCL1 rearrangement was detected in 7/9 (78%) cases, including one case with only about 10% FISH-positive signals. In this same group, TCL1 expression was detected by IHC in 18 of 23 (78%) patients. In patients with an abnormal karyotype without 14q32 abnormality or t(X;14), the cases were further separated by the presence or absence of i(8)(q10). The overall rate of detecting TCL1 rearrangement by FISH was 83% and IHC detected TCL1 expression in 67%, showing no statistical difference between cases with or without i(8)(q10).

    View this table:
    Table 2

    Karyotype, TCL1 FISH and TCL1 IHC of patients with T cell prolymphocytic leukaemia

    In total, TCL1 rearrangement was indicated by karyotyping (inv(14) or add(14)(q32)) with or without FISH confirmation in 30 patients, and solely by FISH in 12 patients. A major discrepancy between cytogenetic and IHC studies was seen in five patients. In detail, 2/42 cases with TCL1 rearrangement were completely negative for TCL1 protein overexpression, and conversely three cases negative by FISH showed TCL1 protein expression by IHC (table 3). In the latter group, one case showed subset TCL1 staining (<30% tumour cells). Minor discrepancy in terms of the percentage of cells with TCL1 rearrangement versus TCL1 expression by IHC was observed in another four patients. Detailed information is shown in online  supplementary table .

    Supplementary file 1

    View this table:
    Table 3

    Concordance and discordance between TCL1 rearrangement and TCL1 overexpression by immunohistochemistry (IHC)

    For the 18 cases of T-PLL with atypical morphology, TCL1 IHC was positive in 15/18 (83%) cases, a rate similar to that (81%) of the entire cohort.

    There were 12 cases negative for TCL1 by IHC, two were positive by TCL1 FISH, two had t(X;14) and one with i8q abnormality. Of the remaining seven patients, five had a normal karyotype, two had a complex karyotype and one with –Y abnormalities only. TCL1 FISH was not performed due to lack of material. These cases had predominantly blood and BM involvement by small to medium-sized cells, five with nucleoli and two without.

    Treatment and outcomes

    Within the follow-up period (median 19.1 months, range 2.6–109.3) and over the course of disease, only four patients were not treated, but the follow-up period was short for these patients (4.6–9.7 months). One patient was treated with single agent bendamustine, and another patient was only treated with supportive measures due to critical condition and passed away shortly. The remaining patients were treated with Campath (anti-CD52 antibody, alemtuzumab), with low-dose or high-dose chemotherapy. Of note, a subset of these patients had a period of ‘wait and watch’ before initiation of therapy. A total of 18 patients received allogeneic stem cell transplant (SCT). As a cohort, the median overall survival was 26 months (2.7–109.3 months), and there were 55 deaths. Of the 14 patients who were alive at the last follow-up, four received SCT. There was no survival difference between patients with TCL1 IHC positive (n=43) versus negative or only subset TCL1 expression (n=14) (OS 24 months vs 26 months, p=0.431).

    Discussion

    Here we studied a large cohort of patients with a diagnosis of T-PLL with the goal of determining the diagnostic utility of karyotype, FISH for TCL1 rearrangement and IHC for TCL1 expression. We showed that detection of inv(14q11) or 14q32 abnormalities by karyotype, TCL1 rearrangement by FISH and/or TCL1 overexpression by IHC were in concordance in about 85% of patients with T-PLL. However, there were discrepancies observed that might complicate establishing the diagnosis of T-PLL in a subset of patients. In particular, conventional cytogenetics was insensitive and appeared to be normal in about one-third of patients, and FISH and IHC were discrepant in about 10% of cases.

    The information provided by this study, to our best knowledge, is not available in the literature, but is needed to guide the application of ancillary test results in the diagnosis of T-PLL. T-PLL is currently defined based on clinicopathological features as a mature, post-thymic T cell neoplasm with a leukaemic presentation. The tumour cells in T-PLL are described typically as small to medium-sized lymphocytes containing single conspicuous nucleoli and showing frequent cytoplasmic blebs. However, other morphological variants have been acknowledged in the WHO classification. In this series, about 70% of T-PLL cases had the classic morphological features; however, in about 30% of cases, tumour cell nucleoli were either completely absent or only discernible in a small subset of tumour cells. In some of these cases, tumour cell nuclear contours were wrinkled or irregular or even overtly cerebriform rather than being round. These cases were similar to what have been described in literature as ‘small cell variant’ T-PLL or T-PLL mimicking Sézary syndrome.2 17 18 It has been shown by others that the small cell variant may have an indolent clinical behaviour.6 19 20 In addition, three cases in this study had mainly medium to large-sized cells, unlike typical T-PLL, but showing TCL1 rearrangement and TCL1 expression. These morphological variants posed diagnostic difficulty and challenges, and in a significant subset of these cases a diagnosis of T-PLL was reached only after ancillary testing.

    We also noted more morphological and immunophenotypical heterogeneity in BM than previously reported in the literature. As expected, in most patients with T-PLL, the BM showed a leukaemic and interstitial infiltrative pattern. In about 15% of cases, however, the BM showed a nodular/aggregative pattern resembling a lymphoma involvement. Immunophenotypically, the tumour cells were most often CD4+CD8−- (~70%), but 28% of cases were CD4+CD8+, and 2% of cases were CD4−CD8+. This distribution is similar to what has been reported by others.3 17 21 22 Most cases of T-PLL were sCD3+, CD7+ and CD26+ as expected; however, there were 7% cases with only partial or dim CD7 expression, 9% cases were negative for surface CD3 and 16% cases were CD26-negative. These variations of T-PLL can make it challenging to distinguish T-PLL from other mature T cell neoplasms, especially a CD4+ PTCL with a leukaemic presentation.

    For the above reasons, we focused on the relative utility of karyotype, FISH for TCL1 rearrangement and IHC to assess TCL1 expression as ancillary tools to establish the diagnosis of T-PLL. Chromosome 14 abnormalities including inv(14)(q11q32) and t(14;14)(q11;q32) involving TCL1 have been reported in up to 80% of cases of T-PLL in the literature and therefore have become the hallmarks of this neoplasm.6 8 9 23 In this study, we showed that combining karyotypic abnormalities of 14q11 and TCL1 rearrangement by FISH, TCL-1 rearrangement was positive in 89% cases tested, a rate similar to what was reported by Stengel and colleagues of 80%.24 TCL1 rearrangement was confirmed by FISH in 100% of patients with an abnormal karyotype containing inv(14)(q11q32). Additionally, in three cases with add(14)(q32), FISH was positive for TCL1 rearrangement in 2/2 cases performed, which suggests that a different partner gene other than TRA might be involved. In patients with a karyotype that did not show 14q32 abnormalities, TCL1 rearrangement was detected in 12/15 (80%) patients, including 7/9 (78%) patients with a normal karyotype and 5/6 (83%) patients with a complex karyotype. In the 12 patients who did not show 14q32 rearrangement by chromosomal analysis, but did show TCL1 rearrangement by FISH, failure of T-PLL cells growth (for patients with a normal karyotype) or a cryptic rearrangement involving 14q32 (for patients with complex karyotype) is likely to be the explanation for the discrepancy. These findings indicate that in the presence of inv(14)(q11q32) or add(14)(q32) or other arrangement (likely translocation) involving 14q32 in T-PLL, it is reasonable to assume the presence of TCL1 rearrangement. In patients without 14q32 abnormalities by karyotyping, FISH can detect TCL1 rearrangement in up to 80% of patients; therefore, FISH is helpful to confirm a diagnosis of T-PLL as it is known that TCL1 rearrangement is specific in T-PLL but not found in PTCL.8

    The results of this study also show that IHC to assess TCL1 expression has great value in T-PLL diagnosis. TCL1 overexpression can be demonstrated by western blot, intracytoplasmic flow cytometry and IHC, and has been reported in 50%–77% cases by various methods.5 6 25–27 It is known that TCL1 is negative in normal T cells, and TCL1 rearrangement is absent in various other types of T cell neoplasms.8 TCL1 protein expression was reported to be absent in T cell neoplasms other than T-PLL in a small series.28 We performed TCL1 IHC on seven PTCL cases with BM and PB involvement; all were negative (data not shown). Of note, a definitive conclusion of TCL1 expression in other T cell neoplasms will require large-scale studies. In a normal BM, TCL1 may stain some normal precursor B cells (hematogones),29 plasmacytoid dendritic cells or reactive germinal centres if lymphoid follicles are present.30 In this study, TCL1 assessed by IHC on paraffin-embedded, decalcified BM trephine biopsy samples was positive in about 80% of patients. It is noteworthy that subset expression (in <30% tumour cells) was observed in 8/51 (16%) cases, including 2 cases where FISH was performed showing TCL1 rearrangement in most of the tumour cells. Different levels of TCL1 expression have been observed in T-PLL by real-time quantitative PCR28 or by IHC.6 A high level of TCL1 oncoprotein expression has been associated with a higher WBC count at presentation, faster tumour cell doubling and enhanced in vitro growth response to T cell receptor engagement.6 We did not find survival difference in patients with a positive TCL1 versus a negative or only subset +TCL1; however, the TCL1 IHC intensity was not scored due to the subjectivity of such evaluation by IHC. Of patients with TCL1 rearrangement that was demonstrated either by karyotype, FISH or both, there were two patients who showed no TCL1 overexpression, whereas TCL1 overexpression by IHC was detected in three patients with no TCL1 rearrangement, giving an overall discordance of 11%. The discordance indicates that TCL1 rearrangement may not always lead to TCL1 oncoprotein overexpression or activation, and conversely TCL1 oncoprotein can be activated through other mechanism other than TCL1 gene rearrangement, such as hypomethylation of the TCL1 promoter region.10 Importantly, in patients with a karyotype showing no 14q32 abnormalities TCL1 overexpression was seen in 26/35 (74%) patients. Importantly, two patients with t(X;14)(q28;q11) shown by conventional cytogenetic and presumably fusing TRA/D with MTCP were negative for TCL1 overexpression by IHC. i(8)(q10), another recurrent karyotypic abnormality in T-PLL, was found in 21 of 44 patients (48%). It is suggested that i(8)(q10) leads to increased expression of the MYC (8q24)7 and a deleterious loss of tumour suppressor genes on 8 p such as MTUS1, synergistically contributing to the pathogenesis of T-PLL. Interestingly, in our study, there were six patients having i(8)(q10) but no 14q32 abnormalities, TCL1 FISH was positive in 2/3, and TCL1 IHC positive in 5/6, suggesting that i(8)(q10) is likely a secondary genetic event, and TCL1 aberrancies may still play a pivotal role in the pathogenesis of T-PLL. Furthermore, of 18 cases with atypical cell morphology, TCL1 IHC was positive in 15/18 (83%) cases. A simple IHC staining would provide a quick confirmation of the diagnosis of T-PLL, especially in patients with atypical morphological and immunophenotypical features.

    In summary, conventional karyotyping is important to reveal the wide landscape of karyotypic aberrancies associated with T-PLL, which are detected in almost two-thirds of patients. Characteristic 14q32 abnormalities or (X;14)(q28;q11) corresponding to the presence of TCL1 or MTCP 7 rearrangement are found in nearly half of the patients by karyotyping. In the remaining patients with no 14q32 karyotypic abnormalities, FISH detects TCL1 rearrangement in about 80% cases and IHC shows TCL1 expression in about 80% patients. FISH and IHC are concordant in the detection of TCL1 in 90% cases. Practically, TCL1 by IHC is highly recommended for screening and establishing a diagnosis of T-PLL, especially in cases that are morphologically and immunophenotypically atypical. FISH for TCL1 rearrangement can be performed as a complementary test to IHC since in a small subset of cases TCL1 expression may be partial and weak, even negative.

    Take home messages

    • Conventional cytogenetics is insensitive in detecting 14q32/TCL1 rearrangements but provides more complete information of the chromosomal landscape of T cell prolymphocytic leukaemia (T-PLL).

    • TCL1 by immunohistochemistry (IHC) is highly recommended for confirming a diagnosis of T-PLL, especially in morphologically and immunophenotypically atypical cases; however, a negative TCL1 IHC result does not exclude a diagnosis of T-PLL.

    • Fluorescence in situ hybridisation for TCL1 rearrangement generally correlates with TCL1 expression by IHC, but can be very valuable in TCL1-negative or weakly/partially expressed cases.

    Acknowledgments

    We thank the cytogenetic laboratory at MDACC for their technical support.

    References

    1. ↵
      Catovsky D M-HH, Ralfkiaer. WHO classification of Tumours of Haematopoietic and Lympoid Tissues. Lyon, France: IARC, 2008.
    2. ↵
      2. Matutes E ,
      3. Garcia Talavera J ,
      4. O’Brien M , et al
      . The morphological spectrum of T-prolymphocytic leukaemia. Br J Haematol 1986;64:111–24.doi:10.1111/j.1365-2141.1986.tb07579.x
      OpenUrlCrossRefPubMedWeb of Science
    3. ↵
      2. Chen X ,
      3. Cherian S
      . Immunophenotypic characterization of T-cell prolymphocytic leukemia. Am J Clin Pathol 2013;140:727–35.doi:10.1309/AJCPG71KYOXTKLQW
      OpenUrlCrossRefPubMed
    4. ↵
      2. Cavazzini F ,
      3. Cuneo A ,
      4. Bardi A , et al
      . Indolent T-cell prolymphocytic leukemia: a case report and a review of the literature. Am J Hematol 2003;74:145–7.doi:10.1002/ajh.10398
      OpenUrlPubMed
    5. ↵
      2. Yokohama A ,
      3. Karasawa M ,
      4. Takada S , et al
      . Prolonged survival in two cases of T-prolymphocytic leukemias with complex hypodiploid chromosomal abnormalities. J Med 2000;31:183–94.
      OpenUrlPubMed
    6. ↵
      2. Herling M ,
      3. Patel KA ,
      4. Teitell MA , et al
      . High TCL1 expression and intact T-cell receptor signaling define a hyperproliferative subset of T-cell prolymphocytic leukemia. Blood 2008;111:328–37.doi:10.1182/blood-2007-07-101519
      OpenUrlAbstract/FREE Full Text
    7. ↵
      2. Maljaei SH ,
      3. Brito-Babapulle V ,
      4. Hiorns LR , et al
      . Abnormalities of chromosomes 8, 11, 14, and X in T-prolymphocytic leukemia studied by fluorescence in situ hybridization. Cancer Genet Cytogenet 1998;103:110–6.doi:10.1016/S0165-4608(97)00410-X
      OpenUrlCrossRefPubMedWeb of Science
    8. ↵
      2. Feldman AL ,
      3. Law M ,
      4. Grogg KL , et al
      . Incidence of TCR and TCL1 gene translocations and isochromosome 7q in peripheral T-cell lymphomas using fluorescence in situ hybridization. Am J Clin Pathol 2008;130:178–85.doi:10.1309/PNXUKA1CFJMVGCN1
      OpenUrlCrossRefPubMed
    9. ↵
      2. Pekarsky Y ,
      3. Hallas C ,
      4. Croce CM
      . Molecular basis of mature T-cell leukemia. JAMA 2001;286:2308–14.doi:10.1001/jama.286.18.2308
      OpenUrlCrossRefPubMedWeb of Science
    10. ↵
      2. Yuille MR ,
      3. Condie A ,
      4. Stone EM , et al
      . TCL1 is activated by chromosomal rearrangement or by hypomethylation. Genes Chromosomes Cancer 2001;30:336–41.doi:10.1002/gcc.1099
      OpenUrlCrossRefPubMedWeb of Science
    11. ↵
      2. Gritti C ,
      3. Dastot H ,
      4. Soulier J , et al
      . Transgenic mice for MTCP1 develop T-cell prolymphocytic leukemia. Blood 1998;92:368–73.
      OpenUrlAbstract/FREE Full Text
    12. ↵
      2. Laine J ,
      3. Künstle G ,
      4. Obata T , et al
      . The protooncogene TCL1 is an Akt kinase coactivator. Mol Cell 2000;6:395–407.doi:10.1016/S1097-2765(00)00039-3
      OpenUrlCrossRefPubMedWeb of Science
    13. ↵
      2. Hiromura M ,
      3. Okada F ,
      4. Obata T , et al
      . Inhibition of Akt kinase activity by a peptide spanning the betaA strand of the proto-oncogene TCL1. J Biol Chem 2004;279:53407–18.doi:10.1074/jbc.M403775200
      OpenUrlAbstract/FREE Full Text
    14. ↵
      2. Despouy G ,
      3. Joiner M ,
      4. Le Toriellec E , et al
      . The TCL1 oncoprotein inhibits activation-induced cell death by impairing PKCtheta and ERK pathways. Blood 2007;110:4406–16.doi:10.1182/blood-2006-11-059501
      OpenUrlAbstract/FREE Full Text
    15. ↵
      2. Loghavi S ,
      3. Wang SA ,
      4. Medeiros LJ , et al
      . Immunophenotypic and diagnostic characterization of angioimmunoblastic T-cell lymphoma by advanced flow cytometric technology. Leuk Lymphoma 2016;57:2804–12.doi:10.3109/10428194.2016.1170827
      OpenUrl
    16. ↵
      2. Shaffer LG M-JJ ,
      3. Schmid M
      . Recommendations of the international standing committee on human cytogenetic nomenclature. Basel, Switzerland: S. Karger, 2013.
    17. ↵
      2. Matutes E ,
      3. Brito-Babapulle V ,
      4. Swansbury J , et al
      . Clinical and laboratory features of 78 cases of T-prolymphocytic leukemia. Blood 1991;78:3269–74.
      OpenUrlAbstract/FREE Full Text
    18. ↵
      2. Rashidi A ,
      3. Fisher SI
      . T-cell chronic lymphocytic leukemia or small-cell variant of T-cell prolymphocytic leukemia: a historical perspective and search for consensus. Eur J Haematol 2015;95:199–210.doi:10.1111/ejh.12560
      OpenUrl
    19. ↵
      2. Foucar K
      . Mature T-cell leukemias including T-prolymphocytic leukemia, adult T-cell leukemia/lymphoma, and Sézary syndrome. Am J Clin Pathol 2007;127:496–510.doi:10.1309/KWJYBCCGTB90B6AE
      OpenUrlCrossRefPubMed
    20. ↵
      2. Kussick SJ ,
      3. Wood BL ,
      4. Sabath DE
      . Mature T cell leukemias which cannot be adequately classified under the new WHO classification of lymphoid neoplasms. Leukemia 2002;16:2457–8.doi:10.1038/sj.leu.2402715
      OpenUrlCrossRefPubMed
    21. ↵
      2. Garand R ,
      3. Goasguen J ,
      4. Brizard A , et al
      . Indolent course as a relatively frequent presentation in T-prolymphocytic leukaemia. Groupe Français d’Hématologie Cellulaire. Br J Haematol 1998;103:488–94.
      OpenUrlCrossRefPubMedWeb of Science
    22. ↵
      2. Krishnan B ,
      3. Matutes E ,
      4. Dearden C , et al.
      Semin Oncol 2006;33:257–63.
      OpenUrlCrossRefPubMed
    23. ↵
      2. Pekarsky Y ,
      3. Hallas C ,
      4. Croce CM
      . The role of TCL1 in human T-cell leukemia. Oncogene 2001;20:5638–43.doi:10.1038/sj.onc.1204596
      OpenUrlCrossRefPubMedWeb of Science
    24. ↵
      2. Stengel A ,
      3. Kern W ,
      4. Zenger M , et al
      . Genetic characterization of T-PLL reveals two major biologic subgroups and JAK3 mutations as prognostic marker. Genes Chromosomes Cancer 2016;55:82–94.doi:10.1002/gcc.22313
      OpenUrlCrossRef
    25. ↵
      2. Herling M ,
      3. Khoury JD ,
      4. Washington LT , et al
      . A systematic approach to diagnosis of mature T-cell leukemias reveals heterogeneity among WHO categories. Blood 2004;104:328–35.doi:10.1182/blood-2004-01-0002
      OpenUrlAbstract/FREE Full Text
    26. ↵
      2. Valbuena JR ,
      3. Herling M ,
      4. Admirand JH , et al
      . T-cell prolymphocytic leukemia involving extramedullary sites. Am J Clin Pathol 2005;123:456–64.doi:10.1309/93P42RNG5XBG3KBE
      OpenUrlCrossRefPubMed
    27. ↵
      2. Aggarwal N ,
      3. Pongpruttipan T ,
      4. Patel S , et al
      . Expression of S100 protein in CD4-positive T-cell lymphomas Is often associated with T-cell prolymphocytic leukemia. Am J Surg Pathol 2015;39:1679–87.doi:10.1097/PAS.0000000000000496
      OpenUrl
    28. ↵
      2. Yokohama A ,
      3. Saitoh A ,
      4. Nakahashi H , et al
      . TCL1A gene involvement in T-cell prolymphocytic leukemia in Japanese patients. Int J Hematol 2012;95:77–85.doi:10.1007/s12185-011-0986-5
      OpenUrlCrossRefPubMed
    29. ↵
      2. Hu Z ,
      3. Li S ,
      4. Medeiros LJ , et al
      . TCL-1-positive hematogones in a patient with T-cell prolymphocytic leukemia after therapy. Hum Pathol 2017.
    30. ↵
      2. Said JW ,
      3. Hoyer KK ,
      4. French SW , et al
      . TCL1 oncogene expression in B cell subsets from lymphoid hyperplasia and distinct classes of B cell lymphoma. Lab Invest 2001;81:555–64.doi:10.1038/labinvest.3780264
      OpenUrlCrossRefPubMedWeb of Science

    Footnotes

    • Handling editor Mary Frances McMullin.

    • Contributors YS, GT, ZH, BT, RM and SAW collected data, performed the experiment, organised the data and contributed to the writing of the manuscript. SAW and LJM designed the study and wrote the manuscript.

    • Competing interests None declared.

    • Ethics approval IRB.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data sharing statement The data are solely owned by the authors and not shared with any other parties.