Familial persistent polyclonal B-cell lymphocytosis

Histological and immunohistochemical features of the spleen in persistent polyclonal B-cell lymphocytosis closely mimic splenic B-cell lymphoma

Persistent polyclonal B-cell lymphocytosis (PPBL) is rare and intriguing hematological disorder predominantly reported in young to middle- aged smoking women. It is characterized by persistent moderate polyclonal B-cell lymphocytosis with circulating hallmark binucleated lymphocytes and elevated polyclonal serum IgM. Most patients have benign clinical course on long-term follow-up. Some pathologic features of PPBL may resemble malignant lymphoma, including morphology as well as frequent cytogenetic and molecular abnormalities. Significant symptomatic splenomegaly requiring splenectomy is very unusual for this disorder; therefore there is a lack of descriptions of the morphologic features of the spleen in the literature. We present here one of the first detailed descriptions of the morphologic and immunohistochemical features of the spleen from a young female with PPBL who developed massive splenomegaly during 6-year follow up. Splenectomy was performed for symptomatic relief and suspicion of malignant process. The morphological and immunohistochemical features of the spleen closely mimicked involvement by B-cell lymphoma, however there was no monotypic surface light chain restriction seen by flow cytometry and no clonal rearrangement of IgH gene was detected by molecular analysis. Evaluating a splenectomy sample in cases like this may present a diagnostic challenge to pathologists. Therefore, correlation with B cell clonality studies (by flow cytometry and molecular analysis), clinical findings and peripheral blood morphology searching for characteristic binucleated lymphocytes is essential to avoid misdiagnosing this benign process as B-cell lymphoma. We also present here a literature review on pathogenesis of PPBL.

Polyclonal B-cell lymphocytosis with binucleated lymphocytes (PPBL)

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare and recently described entity. The review of the literature show PPBL is diagnosed predominantly but not exclusively in women, usually smokers. PPBL is recognized by a moderate, chronic and absolute lymphocytosis (>4 × 10(9)/l) in the peripheral blood. In 10% of cases without lymphocytosis, the PPBL diagnosis has to be suggested by peripheral blood examination showing in all cases atypical binucleated lymphocytes. A polyclonal serum IgM is also associated and HLA-DR7 expression is present in most cases. Contrary to B-cell chronic lymphoproliferative disorders (B-CLPD), peripheral B cells are polyclonal with kappa and lambda light-chain expression and no clonal rearrangement of immunoglobulin heavy chain genes is usually demonstrated. The detection of an extra isochromosome for the long arm of chromosome 3 +i(3)(q10) has to be considered as a specific marker of PPBL. We performed conventional cytogenetic analysis (CCA) in 111 patients with typical PPBL we followed-up more than 4 years. +i(3q) was detected in 34% (33/98), PCC in 8% (8/98) and both abnormalities in 31% (30/98). CCA showed neither +i(3q) nor PCC in 28% (27/98). Fluorescence in situ hybridization (FISH) was also performed in 84 cases and +i(3q) was detected in 71% (60/84). When combining both procedures in 84 patients, +i(3q) was detected in 17 patients with negative CCA and was confirmed in 43 patients with positive CCA. CCA and FISH were both negative in 24 cases. Whether patients with PPBL are at increased risk of hematological malignancy remains unclear. After a median follow-up of 4.4 years, most PPBL patients presented a stable clinical and biological course. Six patients died from pulmonary cancer, myocardial infarction, cerebral aneurysm rupture or diffuse large B-cell lymphoma. Two patients had IgM monoclonal gammopathy of undetermined significance (MGUS) at the time of PPBL diagnosis and two other patients developed IgM MGUS respectively 12 and 22 years after PPBL diagnosis. A malignant non Hodgkin's lymphoma (NHL) appeared in 3 additional patients: two patients presented diffuse large B cell lymphoma and 1 patient a splenic marginal zone lymphoma. In conclusion, the possibility of PPBL to evolve toward a clonal proliferation, malignant lymphoma or secondary solid cancer lead us to consider PPBL not as a benign pathology. We recommend a careful and continued clinical and biological long-term follow-up in all PPBL patients.

[Asymptomatic 32 year old female smoker with persistent polyclonal lymphocytosis]

A 32 year old female smoker (20 pack years) presented with an asymptomatic lymphocytosis of 13,000/nl and splenomegaly. The patient's blood smear showed an absolute lymphocytosis with 65% atypical lymphocytes. A total of 1% of the lymphocytes were bilobulated. Bone marrow histology and immunphenotyping of blood and bone marrow excluded leukemia and non-Hodgkin's lymphoma. IgH-CDR-3 PCR analysis revealed a polyclonal pattern. In summary, a persistent polyclonal B-cell-lymphocytosis (PPBL) was diagnosed. The exact etiology of PPBL is still unclear, however, it is associated with a polyclonal raise in the lymphocyte count of CD27+IgD+-memory-B-lymphocytes due to a defect in apoptosis signaling and leukocyte homing to secondary lymphoid tissues. An association with cigarette smoking is obvious since all patients are smokers. From all published cases, only two developed a malignancy with an uncertain association with PPBL. We have been monitoring our patient for 6.5 years without any evidence of the development of a lymphoma.

Functional T-cell anergy in a case of persistent polyclonal B-cell lymphocytosis

The T-cell population of a patient with persistent polyclonal B-cell lymphocytosis (PPBL) presenting with an intermittent Epstein-Barr virus (EBV)-associated disease was studied. Unstimulated T-cells did not express CD40 ligand (CD40L), whereas activation with IL-2 led to expression of this costimulatory molecule. CD40L expression was inhibited upon incubation with the supernatant of an EBV-positive B-cell line (SM) which had been grown spontaneously from the patient's peripheral blood cells. The supernatant of SM cells effectively inhibited cytotoxic T-cells. Elevated levels of IL-10, TNF-alpha and soluble CD40 were found in the supernatant of SM cells. Additionally, enhanced levels of LMP-1 protein were detected.

Persistent polyclonal B-cell lymphocytosis is an expansion of functional IgD(+)CD27(+) memory B cells

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare disorder of unknown aetiology affecting predominantly young to middle-aged women. It is characterized by a polyclonal expansion of B cells, including typical binucleated lymphocytes, and is associated with the presence of the translocation t(14;18), involving the bcl-2 oncogene. The stage of differentiation of the B cells expanded in PPBL is not known. We analysed the immunophenotype of the expanded B-cell subset in five new patients with PPBL and found a large uniform expansion of a recently defined human memory B-cell population, IgD(+)CD27(+) memory B cells. After in vitro stimulation with interleukin 2 (IL-2) and Staphylococcus aureus Cowan strain I, B cells from PPBL patients produced high levels of IgM immunoglobulins, which is a characteristic feature of IgD(+)CD27(+) memory B cells. Using a quantitative real-time polymerase chain reaction method, we found a high frequency of the translocation t(14;18) in the range of 1000-3000 per 106 B cells in PPBL patients. In contrast, a much smaller number of cells with a t(14;18) was found in B cells from healthy individuals. Our finding that PPBL is an accumulation of memory B cells further suggests that chronic antigeneic stimulation plays an important part in the pathogenesis of this disorder. This IgD(+)CD27(+) memory B-cell population might harbour a certain number of 'physiological' t(14;18) translocations that increases as this population expands in PPBL patients and constitutes the majority of peripheral blood lymphocytes.