Lack of myeloid differentiation primary response protein MyD88 L265P mutation in primary cutaneous marginal zone lymphoma

An unusual case of cutaneous Waldenström macroglobulinemia with the MYD88 L265P mutation

Waldenström macroglobulinemia is a lymphoplasmacytic lymphoma with bone marrow involvement and a monoclonal IgM gammopathy. Infiltration of the skin by neoplastic cells is very rare, and it can be difficult to distinguish from marginal zone lymphoma. The MYD88 L265P mutation is strongly associated with Waldenström macroglobulinemia, and it may be helpful in differentiating the two disorders, although the presence of this mutation is not specific, and other factors must be considered when making the final diagnosis. We present a diagnostically challenging case of cutaneous Waldenström macroglobulinemia in which the MYD88 L265P mutation was identified in the skin but not in the bone marrow, due to a low tumor burden.

MYD88 in the driver's seat of B-cell lymphomagenesis: from molecular mechanisms to clinical implications

More than 50 subtypes of B-cell non-Hodgkin lymphoma (B-NHL) are recognized in the most recent World Health Organization classification of 2016. The current treatment paradigm, however, is largely based on 'one-size-fits-all' immune-chemotherapy. Unfortunately, this therapeutic strategy is inadequate for a significant number of patients. As such, there is an indisputable need for novel, preferably targeted, therapies based on a biologically driven classification and risk stratification. Sequencing studies identified mutations in the MYD88 gene as an important oncogenic driver in B-cell lymphomas. MYD88 mutations constitutively activate NF-κB and its associated signaling pathways, thereby promoting B-cell proliferation and survival. High frequencies of the hotspot MYD88(L265P) mutation are observed in extranodal diffuse large B-cell lymphoma and Waldenström macroglobulinemia, thereby demonstrating this mutation's potential as a disease marker. In addition, the presence of mutant MYD88 predicts survival outcome in B-NHL subtypes and it provides a therapeutic target. Early clinical trials targeting MYD88 have shown encouraging results in relapsed/refractory B-NHL. Patients with these disorders can benefit from analysis for the MYD88 hotspot mutation in liquid biopsies, as a minimally invasive method to demonstrate treatment response or resistance. Given these clear clinical implications and the crucial role of MYD88 in lymphomagenesis, we expect that analysis of this gene will increasingly be used in routine clinical practice, not only as a diagnostic classifier, but also as a prognostic and therapeutic biomarker directing precision medicine. This review focuses on the pivotal mechanistic role of mutated MYD88 and its clinical implications in B-NHL.

Cutaneous B-cell lymphomas - pathogenesis, diagnostic workup, and therapy

Cutaneous B-cell lymphomas (CBCLs) comprise a group of mature lymphoproliferative B-cell disorders that primarily affect the skin. Characterized by great biological and clinical variability among its various subtypes, CBCLs fundamentally differ from primary nodal or systemic B-cell lymphomas. Given their uncomplicated course and excellent prognosis, lymphoma classifications rank primary cutaneous marginal zone lymphoma (PCMZL) and primary cutaneous follicle center lymphoma (PCFCL) as indolent CBCLs. By contrast, diffuse large B-cell lymphoma, leg type (DLBCL-LT) in particular, represent more aggressive lymphoma variants associated with a poorer prognosis. Therapeutic decisions and diagnostic procedures are based on the exact histological and immunohistochemical classification as well as the exclusion of systemic involvement and thus differentiation from nodal and systemic lymphomas. In this context, the diagnostic workup should also include molecular biology methods. Primary therapeutic options for indolent CBCL lesions include surgery and radiation therapy, as well as systemic treatment with rituximab (anti-CD20 antibody) in case of dissemination. More aggressive CBCLs usually require a combination of rituximab and polychemotherapy, primarily the CHOP regimen or modifications thereof. Given that the pathogenesis and biology of CBCLs has not been conclusively elucidated, and given the limited therapeutic armamentarium available, there is great need for comprehensive research, especially with respect to DLBCL-LT.

Prognostic relevance of protein expression, clinical factors, and MYD88 mutation in primary bone lymphoma

Primary bone lymphomas (PBLs) are composed of malignant lymphoid cells presenting in osseous sites, without supra-regional lymph node or extranodal involvement. We systematically characterized the immunophenotype and the myeloid differentiation factor 88 (MYD88)-L265P gene mutation status in PBL. Clinical data from 19 patients with PBL treated at Nanjing Drum Tower Hospital between 2009 and 2015 were analyzed retrospectively. Protein expression patterns were identified immunohistochemically, and MYD88 mutation was assessed using polymerase chain reaction and direct DNA sequencing. Fifteen patients presented with diffuse large B-cell lymphoma. Clinical factors favoring a good prognosis were an age < 60 years and rituximab treatment. B-cell lymphoma 2 expression was detected in 5/15 diffuse large B-cell lymphoma patients, and was associated with a poor prognosis in a univariate model. Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling factors were upregulated in PBLs. All eighteen evaluable PBL samples harbored wild-type MYD88. These data thus suggest that age and rituximab treatment are independent prognostic factors determining overall survival, and that activation of JAK/STAT3 signaling may promote the pathogenesis of PBL. Moreover, the absence of MYD88-L265P mutation in PBL indicate there are distinct pathogenetic backgrounds among extranodal lymphomas.

[Treatment of indolent cutaneous B‑cell lymphoma]

Primary cutaneous B‑cell lymphomas are rarely encountered and represent 25% of all cutaneous lymphomas. Follicular B‑cell lymphoma and marginal zone lymphoma belong to indolent subtypes which as a rule have no systemic dissemination and, thus, a mostly unchanged life expectancy. Therefore, skin-directed treatment options such as excision or radiotherapy are usually sufficient to control the disease. In contrast, cutaneous diffuse large B‑cell lymphoma and EBV-associated B‑cell lymphomas of the skin belong to more aggressive entities which demand a systemic first-line upfront therapy with R‑CHOP. Nevertheless, mortality is still high and comparable to that of systemic/nodal large B‑cell lymphomas so that the identification of pathogenetic driver mutations or novel therapeutic targets may pave the way to better target-oriented therapies.

B-Zell-Lymphome der Haut - Pathogenese, Diagnostik und Therapie

Primär kutane B-Zell-Lymphome (PCBCL) beschreiben reifzellige lymphoproliferative Erkrankungen der B-Zell-Reihe, die primär die Haut betreffen. Die Biologie und der klinische Verlauf der einzelnen PCBCL-Subtypen variieren untereinander stark und unterscheiden sich grundsätzlich von primär nodalen und systemischen B-Zell-Lymphomen. Primär kutane Marginalzonenlymphome (PCMZL) und primäre kutane follikuläre Keimzentrumslymphome (PCFCL) werden auf Grund ihres unkomplizierten Verlaufs und ihrer exzellenten Prognose zu den indolenten PCBCL gezählt. Demgegenüber stellen die diffus großzelligen B-Zell-Lymphome, hauptsächlich vom Beintyp (DLBCL, LT) die aggressiveren PCBCL-Varianten mit schlechterer Prognose dar. Für die Ausbreitungsdiagnostik und die Therapieentscheidung sind eine genaue histologische und immunhistochemische Klassifizierung sowie der Ausschluss einer systemischen Beteiligung in Abgrenzung zu nodalen oder systemischen Lymphomen notwendig. Die Diagnostik sollte dabei durch molekularbiologische Untersuchungen unterstützt werden. Therapeutisch stehen für die indolenten PCBCL primär operative und radioonkologische Maßnahmen im Vordergrund sowie eine Systemtherapie mit dem CD20-Antikörper Rituximab bei disseminiertem Befall. Die aggressiveren Varianten sollten in erster Linie mit Kombinationen aus Rituximab und Polychemotherapieschemata wie z. B. dem CHOP-Schema oder Modifikationen davon behandelt werden. Auf Grund der in allen seinen Einzelheiten noch nicht vollständig verstandenen Pathogenese und Biologie sowie des begrenzten Therapiespektrums der PCBCL besteht hier, speziell beim DLBCL, LT, noch erheblicher Forschungsbedarf.

Cutaneous marginal zone lymphomas

Primary cutaneous marginal zone lymphoma (CMZL) is one of the major primary B-cell lymphomas of skin. Two types are recognized: a more common class-chain switched CMZL, and a much less common IgM+ CMZL. The extremely indolent course, together with other features distinct from most other MALT lymphomas, has led some to question whether at least the class-switched cases should be considered an overt lymphoma.