Peripheral T-cell lymphoma (PTCL) is a group of complex clinicopathological entities, often associated with an aggressive clinical course. Angioimmunoblastic T-cell lymphoma (AITL) and PTCL-not otherwise specified (PTCL-NOS) are the 2 most frequent categories, accounting for >50% of PTCLs. Gene expression profiling (GEP) defined molecular signatures for AITL and delineated biological and prognostic subgroups within PTCL-NOS (PTCL-GATA3 and PTCL-TBX21). Genomic copy number (CN) analysis and targeted sequencing of these molecular subgroups revealed unique CN abnormalities (CNAs) and oncogenic pathways, indicating distinct oncogenic evolution. PTCL-GATA3 exhibited greater genomic complexity that was characterized by frequent loss or mutation of tumor suppressor genes targeting the CDKN2A/B-TP53 axis and PTEN-PI3K pathways. Co-occurring gains/amplifications of STAT3 and MYC occurred in PTCL-GATA3. Several CNAs, in particular loss of CDKN2A, exhibited prognostic significance in PTCL-NOS as a single entity and in the PTCL-GATA3 subgroup. The PTCL-TBX21 subgroup had fewer CNAs, primarily targeting cytotoxic effector genes, and was enriched in mutations of genes regulating DNA methylation. CNAs affecting metabolic processes regulating RNA/protein degradation and T-cell receptor signaling were common in both subgroups. AITL showed lower genomic complexity compared with other PTCL entities, with frequent co-occurring gains of chromosome 5 (chr5) and chr21 that were significantly associated with IDH2R172 mutation. CN losses were enriched in genes regulating PI3K–AKT–mTOR signaling in cases without IDH2 mutation. Overall, we demonstrated that novel GEP-defined PTCL subgroups likely evolve by distinct genetic pathways and provided biological rationale for therapies that may be investigated in future clinical trials.

Key Points• PD-L1 expression in neoplastic cells or stromal cells is associated with poor or good prognosis in ATLL, respectively.• Distinction of expression pattern of PD-L1 might be important on the point of prognostic and therapeutic markers in ATLL. The expression of nPD-L1 and miPD-L1 maintained prognostic value for OS in multivariate analysis (P 5 .0322 and P 5 .0014, respectively). This is the first report describing the clinicopathological features and outcomes of PD-L1 expression in ATLL. More detailed studies will disclose clinical and biological significance of PD-L1 expression in ATLL. (Blood. 2016;128(10):1374-1381

Myeloid sarcoma (MS) is an extramedullary tumor of immature myeloid cells. We analyzed 131 patients with MS, including: (1) de novo MS; (2) MS with concomitant acute myeloid leukemia (AML); (3) MS following myelodysplastic syndrome, myeloproliferative neoplasm, or chronic myelogenous leukemia; and (4) MS as a recurrence of AML. The most common development site was the lymph node. Testicular lesions were statistically more frequent in MS as a recurrence of AML than in other types of MS (P=0.0183). MS tended to lack myeloid markers (myeloperoxidase was present in 63.2%, CD68 in 51.3%, CD13 in 48.7%, and CD33 in 48.7% of patients) and express T-cell markers such as CD3 (20.7%) and CD5 (34.2%). All T-cell marker-positive MS cases were negative for the αβ and γδ T-cell receptors on immunohistochemistry. Underlying myelodysplastic syndrome or myeloproliferative neoplasm was a poor prognostic factor (vs. de novo MS: P=0.0383; vs. MS with concomitant AML: P=0.0143). However, there was no statistical difference in prognosis between de novo MS and MS with concomitant AML (P=0.288). There were no significant differences in prognosis between the prognoses of T-cell marker-positive and T-cell marker-negative MS cases. In addition, CXCR4 expression was a poor prognostic factor in MS (P=0.0229). This study involves the largest MS cohort to date and expands the clinical and pathologic knowledge of the disease.

The need for reproducibility in the classification of acute leukaemia has made it necessary to incorporate information derived from new techniques which have become essential for the study of these disorders. In addition to classic morphology and cytochemistry (FAB proposals), it is necessary to add immunology and cytogenetics (MIC proposals), as well as to investigate further the biological and diagnostic significance of molecular events. As a result of these investigations a new group of leukaemias merit recognition as distinct entities. These include three types of ALL with specific chromosome abnormalities, namely, i) t (9;22), ii) t (4;11) and iii) t (1;19) and four subtypes of AML, i) with minimal differentiation or AML-M0, ii) with basophilic precursors or M2Baso, iii) AML (M4/M5) with t (8;16) and iv) AML with trilineage myelodysplasia. Biphenotypic acute leukaemia constitutes also a distinct entity with features of ALL and AML and represents a malignancy probably affecting multipotent stem cells. We propose an objective evaluation system for biphenotypic leukaemias based on a score in which the various lineage markers are graded according to their known specificity.