Case 4 -

Hepatosplenic T-cell Lymphoma (gδ variant) (WHO classification) Dr. Philippe Gaulard, Dept of Pathology, INSERM U617 Hôpital Henri Mondor, 94010 Créteil, France

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Clinical History: A 54-year-old man presented with fatigue, fever and weight loss revealing a major splenomegaly and hepatomegaly, without lymphadenopathy. He had pancytopenia (WC: 1,4: Hb: 7,7; Plt:25) without abnormal circulating cells. The bone marrow biopsy was hypercellular and first interpreted as normal. Clinical staging and CT scan: no lymphadenopathy Retrospective review of the initial bone marrow performed in another institution, disclosed minimal lymphoid infiltration. The patient had an aggressive clinical course, despite intensive polychemotherapy: he died of disease ten months after diagnosis. The image is from the spleen. The liver and bone marrow features will be discussed. Case 4 - Figure 1 Click to view with ImageScope Click to view with a Web-Based Viewer Histologic and phenotypic findings The spleen was massively enlarged (2100 g). At macroscopy, the pattern was homogeneous without nodules, there was no hilar lymphadenopathy. On histopathology, there was a marked reduction of the white pulp with rare residual atrophic white pulp, whereas the red pulp was diffusely invaded by a dense lymphoid infiltrate made of monomorphic small to medium-sized cells with round or slightly irregular nuclei; with rare mitoses. These neoplastic cells were located within the cords and sinuses; Careful review of the bone marrow biopsy disclosed the presence of a subtle, but peculiar sinusal lymphoid infiltration by small/medium-sized cells in a hypercellular bone marrow, which was strongly highlighted by CD3 immunostaining. The liver biopsy showed that the lymphoid infiltrate was preferentially located within the sinusoids. Immunohistochemistry performed on paraffin-embedded material was consistent with a lymphoma of non activated cytotoxic T-cell origin, and reinforced the peculiar distribution of the neoplastic cells specially in the bone marrow. The neoplastic cells were : CD20-, CD3+, CD5-, CD56+ TIA1+, granzyme B- (non activated cytotoxic profile); On frozen sections, they had the phenotype of gδ T cells: CD2+, CD3+, CD5-, CD7+, CD4/CD8-, TCR gδ + (Vd 1+), CD56+. Molecular findings Genotypic studies were consistent with the gδ T cell origin showing: clonal rearrangement of g and δ genes Cytogenetic studies (FISH) disclosed isochromosome 7q. There was no EBV association (in situ hybridization techniques with EBERs probes). Diagnosis: Hepatosplenic T-cell lymphoma (gδ variant) (WHO classification) Differential diagnosis The major diagnostic features of Hepatosplenic T-cell lymphoma (HSTL) are indicated in Table 1. Table 1: Major Diagnostic Features of Hepatosplenic T-cell Lymphoma splenomegaly (without nodules) hepatomegaly no lymphadenopathy thrombocytopenia frequent anemia, leucopenia monomorphic small/medium-sized cells sinusal pattern of infiltration in the bone marrow, the spleen and the liver CD3+, CD5-, CD4-/CD8-, CD56+ phenotype non activated cytotoxic profile (TIA1+, GrB-) isochromosme 7q absence of EBV Among these, the value of the sinusal CD3+ infiltration of the bone marrow needs to be emphasized. The diagnostic may be difficult to ascertain by non experienced pathologists. Due to the better recognition of the subtle infiltrate in the bone marrow and the use of a combined cytological, histopathological, phenotypic and cytogenetic approach, the diagnostic strategy tends to change over time. The diagnosis of the disease was initially based on histopathological and immunohistochemical findings obtained after splenectomy (as in the present case) performed in the past in such patients. It can be reliably established on bone marrow biopsy and/or bone marrow aspirate. The latter should now be recommended first in the diagnostic strategy of the disease, thus avoiding splenectomy for diagnosis. To establish the common gδ TCR expression and to allow cytogenetic studies, frozen tissue specimens or alternatively flow cytometry on marrow cell suspension are essential. The main differential diagnosis include other lymphoma entities which commonly present with hepatosplenic disease and show an infiltration of the splenic red pulp. These are mainly T-or NK-cell neoplasms – ie aggressive NK-cell lymphoma/leukemia, T-cell large granular lymphocyte leukemia - and, among B-cell neoplasms, hairy cell leukemia and splenic marginal zone lymphoma. Overall, the examination of bone marrow biopsy with appropriate panel of immunohistochemical markers are essential for the diagnosis: - Aggressive NK cell lymphoma/leukemia certainly represents the major differential diagnosis of HSTL. Both diseases commonly present as hepatosplenic disease with B symptoms and have an aggressive outcome. Main differences include leukemic pictures, NK cell origin with activated cytotoxic (Granzyme B+/perforin+) phenotype, absence of T cell receptor expression and EBV association as well as the diffuse and interstitial pattern of bone marrow infiltration - often faint - without sinusal predilection which, in addition to severe illness and haemophagocytic syndrome, are common features of aggressive NK cell lymphoma/leukemia. - T-cell granular lymphocytic leukemia (T-LGL) is a chronic, indolent lymphoproliferative disorder with clinical and laboratory manifestations, which are clearly distinct from that observed in HSTL . Most patients are asymptomatic or have symptoms related to variably severe neutropenia, anemia or thrombocytopenia and/or to autoimmune disorders. T-LGL is also characterized by a mild leukemic picture due to a clonal expansion of cytolytic lymphocytes with azurophilic granules, which have a CD3+, CD8+, CD57+, TCRaβ+ phenotype. On histopathology (not required for diagnosis), they have a lymphocytic appearance and, in the bone marrow biopsy, realize a subtle diffuse interstitial infiltrate blending hematopoietic cells, which can show minimal, not elective, sinusal involvement. Othergδ T-cell lymphomas - The demonstration of gδ T-cell phenotype is not specific for the diagnosis of HSTL. Indeed, a proportion of T-lymphoblastic lymphoma, rare cases of T-cell large granular lymphocyte leukemia and a subset of extranodal cytotoxic T-cell lymphomas can also demonstrate a gδ T-cell origin. In agreement with the predilection of normal gδ cells for some epithelia and mucosae, gδ T-cell lymphomas may develop initially in different mucosal tissues such as nasopharyngeal region and intestine, as well as in the skin. Muco-cutaneous gδ T-cell lymphomas are regarded as a subset of activated cytotoxic T-cell lymphomas with heterogeneous clinicopathologic aspects and are likely to belong to other disease entities of T and NK cell lymphomas, such as nasal-type NK/T cell lymphomas or panniculitis-like subcutaneous T-cell lymphomas, suggesting that site of origin and functional properties might be more important than the precise phenotype for their definition. However, the finding that gδ phenotype has a prognostic relevance in cutaneous T-cell lymphomas, has resulted in the recent proposal that cutaneous and mucosal gδ T-cell lymphomas should be categorized separately, according to the WHO-EORTC classification for cutaneous lymphomas. Discussion 1 – HSTL is a distinct clinicopathologic entity, characterized by an hepatosplenic presentation without lymphadenopathy and a poor outcome. The neoplasm results from a proliferation of non activated cytotoxic T cells, usually monomorphic medium-sized, which disclose a peculiar sinusoidal pattern of infiltration in the spleen, the liver and the bone marrow. It is associated with a reccurrent cytogenetic abnormality, the isochromosome 7q. Most cases have been shown to derive from the gδ T cell subset, and the gδ T cell phenotype has been part of the definition of the entity, initially named hepatosplenic gδ T cell lymphoma in the REAL classification. Recently, a few similar cases with a aβ phenotype have been described, and the term hepatosplenic T-cell lymphoma has been preferred in the current WHO classification. HSTL is rare, with approximately 100 cases reported. It is characterized by a male predominance and its occurrence in young adults – or children - with a median age around 35 years. A number of cases have been reported in patients with immune manifestations or with immunodeficiency, specially in patients receiving long term immunosuppressive therapy for solid organ transplantation, or chronic inflammatory diseases such as Crohn's disease. From these observations and in view of the functional properties of normal gδ T cells, it has been postulated that chronic antigen stimulation in the setting of immune defect could play a role in the pathogenesis of the disease. As an example, expansion of gδ T cells is observed in peripheral blood in recipients of renal allografts and gδ T cells display an alloreactive response to various leukocyte antigen molecules . 2 – Although bone marrow involvement is a frequent feature in T-cell lymphoma, the presence of an elective distribution within the sinuses is very suggestive. The latter is highlighted by CD3 immunostaining and on paraffin-embedded sample, a CD3+/CD5-/TIA1+/GrB+ profile is higly suggestive. 3 – Most cases appear to be derived from gδ T cells with expression of TCR δ proteins – which requires frozen material to be evaluated. However, cases with similar clinical presentation, identical CD3+, CD5-, CD56+ phenotype and a non activated cytotoxic profile, but with a b F1+ phenotype have been described. In view of their similar clinical, pathological and genetic features (including iso7q) as well as their identical pattern of expression of NK receptors (KIR), both gδ and aβ HSTL are regarded as variants of the same entity deriving from different subsets of T cells belonging to NK.T cells with similar properties in the innate immune system. References Jaffe ES, Harris NL, Stein H, Vardiman J (Eds): World Health Organization Classification of Tumours. Pathology and genetics of tumours of Haematopoietic and Lymphoid tissues. IARC Press: Lyon, 2001. 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