TY - JOUR T1 - Comparison of karyotyping, <em>TCL1</em> fluorescence in situ hybridisation and TCL1 immunohistochemistry in T cell prolymphocytic leukaemia JF - Journal of Clinical Pathology JO - J Clin Pathol SP - 309 LP - 315 DO - 10.1136/jclinpath-2017-204616 VL - 71 IS - 4 AU - Yi Sun AU - Guilin Tang AU - Zhihong Hu AU - Beenu Thakral AU - Roberto N Miranda AU - L Jeffrey Medeiros AU - Sa A Wang Y1 - 2018/04/01 UR - http://jcp.bmj.com/content/71/4/309.abstract N2 - 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 &gt;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. ER -