Our patient had a mild lymphocytosis. The differentials include:
- Reactive – especially viral illnesses
- Polyclonal B cell lymphocytosis – binucleate lymphocytes with isochrome 3q
- Lymphoproliferative neoplasms such as CLL and other types of lymphoma
In the first instance repeating the FBC is all that is required as it will often normalise. Patients with persistent lymphocytosis without reactive causes should have a history and examination to assess for any complications of CLL/lymphoma e.g. lymphadenopathy, splenomegaly and B symptoms. The rest of the blood count should be reviewed to look for any cytopenias or haemolysis. There are no absolute guidelines of when to refer to a haematologist or when to obtain confirmatory flow cytometry/immunophenotyping. The key is that most of these disorders are slow -growing and most will never need any treatment and therefore mild to moderate lymphocytosis can just be monitored. If the cells appear atypical on the blood film then a haematologist may reflex immunophenotyping.
In this case the lymphocytosis was very mild but increased over time and the morphology was not typical for CLL. By flow there was a kappa restricted B cell population = 19.2 x 109/L which was CD19+, FMC7+, CD23 negative, CD5+, CD79b+, CD10 negative, CD103 negative, CD11c negative, CD38 negative, sIg+ (CLL score 1/5). FISH showed an abnormal CCND1 rearranged signal pattern in 54 of 100 nuclei scored, consistent with a clone with t(11;14)(q13;q32) translocation or other rearrangement of CCND1 (11q13), typical of mantle cell lymphoma.
Mantle cell lymphoma is a type of lymphoma that behaves in both an indolent and aggressive fashion. Patients can undergo active monitoring in the early stages but for this type of lymphoma often treatment is required. This includes R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone) and for fitter patients a regime containing high dose cytarabine followed by an autologous stem cell transplant. Rituximab maintenance therapy is used. Other options for treatment in less fit patients includes bendamustine-rituximab, VR-CAP (rituximab, bortezomib, cyclophosphamide, doxorubicin and prednisolone), R-CVP (rituximab, cyclophosphamide and prednisolone) or rituximab-chlorambucil. Ibrutinib is licenced in the UK for relapsed patients.
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