Lymphomatous variant of hairy cell leukaemia: a distinctive presentation mimicking low-grade B-cell lymphoma

Genomic profiling for clinical decision making in lymphoid neoplasms

With the introduction of large-scale molecular profiling methods and high-throughput sequencing technologies, the genomic features of most lymphoid neoplasms have been characterized at an unprecedented scale. Although the principles for the classification and diagnosis of these disorders, founded on a multidimensional definition of disease entities, have been consolidated over the past 25 years, novel genomic data have markedly enhanced our understanding of lymphomagenesis and enriched the description of disease entities at the molecular level. Yet, the current diagnosis of lymphoid tumors is largely based on morphological assessment and immunophenotyping, with only few entities being defined by genomic criteria. This paper, which accompanies the International Consensus Classification of mature lymphoid neoplasms, will address how established assays and newly developed technologies for molecular testing already complement clinical diagnoses and provide a novel lens on disease classification. More specifically, their contributions to diagnosis refinement, risk stratification, and therapy prediction will be considered for the main categories of lymphoid neoplasms. The potential of whole-genome sequencing, circulating tumor DNA analyses, single-cell analyses, and epigenetic profiling will be discussed because these will likely become important future tools for implementing precision medicine approaches in clinical decision making for patients with lymphoid malignancies.

Utility of Cyclin D1 in the Diagnostic Workup of Hematopoietic Neoplasms: What Can Cyclin D1 Do for Us?

Cyclin D1, encoded by CCND1, promotes cell cycle progression from G1 to S phase. Its expression is induced by MAPK/ERK pathway as well as translocations/rearrangements involving CCND1 gene. The evaluation of cyclin D1 expression by immunohistochemistry plays an important role in the diagnostic workup of various hematopoietic diseases. In this review, we aimed to discuss the value of cyclin D1 immunostain in the diagnosis and different diagnosis of hematopoietic neoplasms.

Morphological and immunophenotypical features of hairy cell leukaemia involving lymph nodes and extranodal tissues

AIMS

Hairy cell leukaemia (HCL) is a rare B cell neoplasm that mainly affects bone marrow (BM), peripheral blood (PB) and spleen. Involvement of lymph nodes and extranodal structures is considered infrequent. Herein we describe our institutional experience of nodal (n = 10) and extranodal (n = 3) HCL during a 30-year period.

METHODS AND RESULTS

Ten patients had prior evidence of HCL within the BM or PB at a median 35.8 months before nodal/extranodal diagnosis (range: <1-175 months), and HCL was diagnosed concurrently within the bone marrow of one additional patient. Nodal involvement showed distinct architectural patterns, including diffuse (62% of cases), sinusoidal (25%) and nodular (13%). Extranodal involvement was characterized as diffuse infiltration through underlying structures in all cases. Morphological features ranged from classic 'fried-egg' cytology to a plasmacytoid appearance. Nodal/extranodal disease showed an overlapping immunophenotypical profile with other small B cell lymphomas, including expression of cyclin D1 (70%), CD43 (55%), CD10 (38%) and CD5 (8%). Rates of both CD43 and CD10 reactivity were higher than described previously in leukaemic HCL, suggesting that expression may be enriched in cases with extramedullary extension.

CONCLUSIONS

Although uncommon, HCL should be considered in the differential diagnosis of small B cell neoplasms involving nodal/extranodal sites, given the therapeutic implications. In particular, recent discoveries including detection of the BRAF^V600E mutation in nearly all cases of HCL and the availability of an antibody to CD103 for use in paraffin-embedded tissues will facilitate the distinction of HCL from other small B cell lymphomas in the nodal/extranodal setting.

Hairy Cell Lymphoma: A Potentially Under-Recognized Entity

Hairy cell leukemia (HCL) is a low grade B-cell lymphoproliferative disorder that typically presents with splenomegaly, cytopenias, and diffuse bone marrow infiltration. There have been few cases in the literature of HCL presenting as lymphomas in extra-nodal locations, such as soft tissues and bones without circulating leukemic cells, splenomegaly, or iliac crest bone marrow involvement. We present an additional case presenting as a thoracic mass, and discuss potential diagnostic pitfalls and management of these rare cases.