Classification of natural killer cell neoplasms

Epidemiology and Pathology of T- and NK-Cell Lymphomas

PURPOSE

This review will describe and update readers on the recent changes in the 2017 WHO classification regarding peripheral T-cell lymphomas.

RECENT FINDINGS

Signficant advances in molecular studies have resulted in revisions to the classification as well as introduction to provisional entities such as breast implant-associated ALCL and nodal PTCL with T-follicular helper phenotype.

SUMMARY

Major advances in molecular and gene expression profiling has expanded our knowledge of these rare and aggressive diseases.

Practical evaluation and management of cutaneous lymphoma

Accurate evaluation of patients with suspected or known cutaneous lymphoma requires the integration of many sources and types of information, including clinical evaluation, microscopic analysis of tissue, immunophenotyping, gene rearrangement studies, clinical staging, and longitudinal observation. Diagnoses should be based on knowledge of specific lymphoma types as described in modern classification systems. Management of patients with cutaneous lymphoma requires collaboration among dermatologists, dermatopathologists, hematopathologists, and medical, surgical and radiation oncologists. (J Am Acad Dermatol 2002;46:325-57.)

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should better understand how to evaluate and manage patients for suspected or established lymphoma of the skin. Components include the clinical history and physical examination, optimal biopsy and tissue handling, interpretation of pathology and adjunctive test results, clinicopathologic correlation, and therapy. Participants should also understand the basis for establishing a specific diagnosis of cutaneous lymphoma based on current classification and staging.

CD4+ CD56+ cutaneous neoplasms: a distinct hematological entity? Groupe Français d'Etude des Lymphomes Cutanés (GFELC)

We report seven cases of particular cutaneous tumors selected from the register of the French Study Group on Cutaneous Lymphomas. The patients (three men, four women) were aged 37-86 years. They initially presented with cutaneous nodules or papules. Three cases presented with regional lymph nodes. Stagings were negative, except for one patient with bone marrow involvement. Histological features were relevant with pleomorphic medium T-cell lymphoma, but these cells exhibited a distinguishing phenotype. They were positive for CD4, CD56, and also CD45, CD43, and HLA-DR. All other T-cell and B-cell markers were negative. The myelomonocytic markers (CD13, CD14, CD15, CD33, CD117, myeloperoxidase, and lysozyme) were negative excepted CD68, which was clearly positive in four cases and weakly in two cases. Others natural killer cell markers (CD16, CD57, TiA1, granzyme B), TdT, and CD34 were negative. Polymerase chain reaction studies did not detect any B or T clonal rearrangement. The cytogenetic studies, performed in five cases, showed a del(5q) in two cases. All patients were treated successfully by polychemotherapy, but relapsed quickly in the skin, between 4 and 28 months. Five patients developed bone marrow involvement, with leukemia in three cases, and they died in 5-27 months. One patient died at 17 months with skin progression. The seventh patient is alive at 33 months, with cutaneous progression. The origin of these cells is unclear. Despite expression of CD4 or CD56, we failed to demonstrate a T-cell, natural killer cell origin. However, CD4 and CD56 are not specific for T or natural killer lineages. Although these two markers are also known to be expressed by monocytic cells, classic myeloid antigens were negative. These seven cases, together with other rare similar cases already reported, seem to represent a distinct entity likely developed from hematological precursor cells.

Utility of a paraffin section-reactive CD56 antibody (123C3) for characterization and diagnosis of lymphomas

Although expression of CD56 (neural cell adhesion molecule, a natural killer cell marker) is uncommon among lymphomas, this feature has defined a distinctive and important category of lymphoma: the putative natural killer (NK) cell lymphoma, which shows a predilection for the upper aerodigestive tract, skin, skeletal muscle, and other extranodal sites and pursues an aggressive clinical course. Thus far, CD56 expression can be reliably analyzed only on fresh or frozen tissues. In this study, we evaluated the sensitivity and specificity of a CD56 antibody, 123C3, when applied on routine formalin-fixed, paraffin-embedded tissues for analysis of lymphomas, by comparing the staining results with those obtained on frozen tissues using the CD56 antibody NKH1. The 123C3 antibody worked on paraffin sections only with prior antigen retrieval using a pressure cooker or a microwave oven. Among 32 CD56+ T/NK cell lymphomas and one CD56+ B-lymphoblastic lymphoma, the neoplastic cells showed crisp membrane staining with 123C3 in all cases. None of the 24 CD56- T-cell lymphomas and 50 CD56-B-cell lymphomas stained with 123C3. In normal or reactive lymphoid tissues from a variety of sites, there were few small lymphocytes (< 0.1%) that showed cell membrane staining with 123C3, although occasional plasma cells might show cytoplasmic staining. We conclude that with suitable antigen retrieval procedures, 123C3 can be reliably applied on routine paraffin sections for detection of CD56 expression in lymphomas. Furthermore, this antibody can be used to support a diagnosis of lymphoma or to detect residual disease for cases of CD56+ T/NK cell lymphoma in which the neoplastic lymphoid cells are small and show minimal atypia, especially in small biopsies.

CD2+, CD3-, CD56/NCAM+ malignant lymphoma with TCR beta gene rearrangement: a case report

A case of CD56/NCAM+ malignant lymphoma is reported. Only a rare malignant lymphoma cell showed azurophilic granules in the cytoplasm of Giesma-stained preparations, while electron microscopic examination revealed occasional cytoplasmic granules with paracrystalline inclusions. The most common phenotype seen in NK lymphomas, CD2+, CD3-, CD56+, CD16-, CD57-, was present in the case. Cases with this phenotype have been interpreted to represent either true NK lymphoma or T-cell lymphoma with NK expression. Genotyping, where performed, has shown TCR germline configuration. Our case showed TCR beta rearrangement indicating that the above phenotype can be associated with a peripheral T-cell lymphoma.

Acute agranular CD4-positive natural killer cell leukemia. Comprehensive clinicopathologic studies including virologic and in vitro culture with inducing agents

BACKGROUND

A 63-year-old male presented with fever, a subcutaneous nodule, gingival hypertrophy, lacrimal gland enlargement, and no lymphadenopathy or hepatosplenomegaly, but had anemia, thrombocytopenia, and peripheral blood (PB) plus bone marrow (BM) involvement by leukemic cells. There was minimal response to multiagent chemotherapy and local radiotherapy, with a survival of 6.5 months from disease diagnosis.

METHODS

The PB and/or BM leukemic cells were evaluated using electron microscopy (EM), immunohistochemistry, flow-cytometric immunophenotyping, cytochemistry, cytogenetics, Southern blot analysis for gene rearrangement and Epstein-Barr virus (EBV), polymerase chain reaction for EBV and human herpes virus-6 (HHV-6), and in vitro culturing with inducing agents.

RESULTS

The leukemic cells were agranular and monocytoid, with a hairy cell-like bone marrow biopsy infiltrate. Myeloperoxidase (MPO) and alpha-naphthyl butyrate esterase staining was negative, and periodic acid-Schiff staining was positive by light microscopy. Electron microscopy showed MPO negativity and a lack of parallel tubular arrays. The immunophenotype was CD3-, CD56+, CD4+, CD8-, CD15+, TCR1-, and TCR2-, with germline immunoglobulin and T-cell receptor genes and an abnormal karyotype (44XY, 5q-, -13, 13q+, -15). No genomic material for EBV or HHV-6 was detected. Cell cultures with butyrate and N,N-hexamethylene bis-acetamide suggested the possible induction of tumor cells to express a T-cell immunophenotype.

CONCLUSION

A case of clonal acute natural killer (NK) cell leukemia with an unusual morphology (agranular) and unique phenotype (CD3-, CD56+, CD4+, CD15+) is presented. Unlike as in other acute NK leukemias, EBV was negative; there was no evidence of HHV-6. The tumor cell, after culturing with differentiating agents, may have been induced to express a T-cell immunophenotype.