A Novel Immunohistochemical Classifier to Distinguish Hodgkin Lymphoma From ALK Anaplastic Large Cell Lymphoma

Claudia Döring; Martin-Leo Hansmann; Claudio Agostinelli; Pier P Piccaluga; Fabio Facchetti; Stefano Pileri; Ralf Küppers; Sebastian Newrzela; Sylvia Hartmann

Disclosures

Mod Pathol. 2014;27(10):1345-1354. 

In This Article

Discussion

Several attempts have been made to establish classifiers differentiating between ALK anaplastic large cell lymphoma and peripheral T-cell lymphoma not otherwise specified,[24–26] but to our knowledge this has not been achieved for differential diagnosis of classical Hodgkin lymphoma and ALK anaplastic large cell lymphoma. The aim of the present study was to find new immunohistochemical markers which can be applied in the differential diagnosis of ALK anaplastic large cell lymphoma and classical Hodgkin lymphoma in daily routine practice. Our classifier was established by the reevaluation of gene expression studies of microdissected tumor cells and shows a high specificity and sensitivity.

Owing to overexpression of several genes in the Hodgkin and Reed-Sternberg cells of classical Hodgkin lymphoma we were able to distinguish between ALK anaplastic large cell lymphoma and classical Hodgkin lymphoma. The one gene overexpressed in ALK anaplastic large cell lymphoma did not prove to be diagnostically powerful. One of the genes upregulated in classical Hodgkin lymphoma was TUBB2B, a member of the beta-tubulin family, involved in the formation of microtubuli and therefore has a role in several important cellular processes, including mitosis. TUBB2B has so far not been described to be upregulated in Hodgkin and Reed-Sternberg cells, whereas another member of the beta-tubulin family, TUBB3, was observed to be expressed in both the tumor cells of classical Hodgkin lymphoma and anaplastic large cell lymphoma.[27] Recently, refusion of Hodgkin and Reed-Sternberg cells with a persisting microtubule bond between daughter cells could be demonstrated to be an important feature of giant cell formation.[28] However, the reason of a selective tubulin overexpression in the Hodgkin and Reed-Sternberg cells as demonstrated in this study so far remains obscure.

The remaining significantly overexpressed genes are related to the interactions between Hodgkin and Reed-Sternberg cells and their microenvironment. CD83 is usually expressed in mature dendritic cells[29] and triggers CD4+ T-cell maturation, but is also expressed by activated B cells and involved in the modulation of B-cell receptor signaling.[30]CD83 has previously been described to be upregulated in Hodgkin and Reed-Sternberg cells of Hodgkin lymphoma.[31] Transgenic overexpression of CD83 in B cells resulted in an upregulation of the major histocompatibility complex II (MHC II) and interleukin 10.[30] However, MHC II is shown to be downregulated in a subset of classical Hodgkin lymphoma cases,[32] partly owing to translocations involving the MHC II transactivator (CIITA).[33] Decreased MHC class II expression has been linked to reduced tumor cell immunogenicity. A strong expression of STAT3 was observed in Hodgkin and Reed-Sternberg cells in the present and previous studies.[34–36]STAT3 is mainly expressed in macrophages and dendritic cells and can exhibit—depending on the stimulating cytokine—both pro- and antiinflammatory properties.[37] However, STAT3 is also found to be expressed in ALK+ anaplastic large cell lymphoma.[38] In contrast, pediatric cases of ALK anaplastic large cell lymphoma were negative for phosphorylated STAT3.[39] Our results fit well with the observations made by Piva et al,[26] when considering the number of ALK anaplastic large cell lymphoma strongly expressing phosphorylated STAT3 in most if not all neoplastic cells. This can also be observed on RNA level in the gene expression arrays (Figure 1). However, it is important to point out, that in the present study only the amount of STAT3 protein was assessed, whereas phosphorylation and activation status were not evaluated. MDC/CCL22 is usually also expressed by antigen-presenting cells and is upregulated by TH2-type cytokines.[40] It was shown to be expressed in Hodgkin and Reed-Sternberg cells of classical Hodgkin lymphoma[41] and age-related Epstein–Barr virus-associated B-cell lymphoproliferative disorders.[42]MDC/CCL22 and TARC/CCL17 share the receptor CCR4, by which TH2 and regulatory T cells can be attracted by Hodgkin and Reed-Sternberg cells.[43,44] However, it could recently be shown that the majority of T cells in classical Hodgkin lymphoma microenvironment represents TH1 cells.[45]

In conclusion, three of four genes overexpressed in the Hodgkin and Reed-Sternberg cells in comparison with the tumor cells of ALK anaplastic large cell lymphoma are also expressed in antigen-presenting cells and are related to the interactions between Hodgkin and Reed-Sternberg cells and surrounding T cells. Moreover, Hodgkin and Reed-Sternberg cells are known to express several additional markers usually expressed by antigen-presenting cells.[46–48]Although Hodgkin and Reed-Sternberg cells have usually lost their B-cell phenotype, they have maintained the features for an interaction with T cells, which is not observed in the tumor cells of ALK anaplastic large cell lymphoma. Interestingly, Hodgkin lymphoma cases with granzyme B expression were less frequently positive for MDC/CCL22 and CD83 than conventional classical Hodgkin lymphoma cases. These cases may therefore differently interact with their microenvironment and may be closely related to anaplastic large cell lymphoma.

In summary, the genes identified in the present study reflect a different pathogenesis of classical Hodgkin lymphoma and ALK anaplastic large cell lymphoma. By closely interacting with surrounding T cells, Hodgkin and Reed-Sternberg cells have maintained parts of their B-cell identity and show a fundamentally different interaction with their microenvironment than tumor cells in ALK anaplastic large cell lymphoma. These features can be practically applied in the diagnostic distinction between classical Hodgkin lymphoma and ALK anaplastic large cell lymphoma. However, owing to the limited case number investigated in the present study, our newly established classifier should be validated in a large patient series with clinical data.

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