An 86 year old male presented to the Casualty Department with chest pain.

On clinical examination he was noted to have a splenomegaly. No lymphadenopathy was detected.

A FBC was performed with the following results:

Hb 114 g/L, WBC 13.5 x 10⁹/L and platelet count 258 x 10⁹/L

The blood film showed a mild lymphocytosis.

23% of the lymphocytes had the appearance of those seen in splenic marginal zone lymphoma in that they had round nuclei with cytoplasmic villi distributed towards one pole of the cell.

Immunophenotyping and cytogenetics were performed on the bone marrow with the following results:

Immunophenotype:
SIg⁺, HLA-DR⁺, CD19⁺, CD20⁺, CD22⁺, CD23⁺(weak), CD10^–, 11c⁺, CD25^–, FMC7⁺, CD3^–, CD5^– and CD103⁺

Cytogenetics:
del(7q)

A diagnosis of splenic marginal zone lymphoma (SMZL) was made.

Splenic marginal zone lymphoma

SMZL is a rare B-cell lymphoma occurring in elderly patients. It comprises less than 1% of all the lymphoid neoplasms. SMZL is characterised by a large spleen while lymphadenopathy is rare. The bone marrow (BM) and peripheral blood (PB) are often involved. The PB shows a moderate lymphocytosis with white cell counts of less than 25 x 10⁹/L. The lymphocytes appear as villous lymphocytes.

Morphologically these lymphocytes range from small to medium in size with round to irregular shaped nuclei, coarse chromatin pattern, an occasional nucleolus and abundant pale blue cytoplasm. The cytoplasm may exhibit fine projections or villi confined to one pole of the cell. Some of the lymphocytes may appear plasmacytoid.

The differential diagnosis includes other small B-cell lymphomas/leukaemias including chronic lymphatic leukaemia, hairy cell leukaemia, mantle cell, follicular and lymphoplasmacytic lymphoma.

Immunophenotyping shows strong expression of surface immunoglobulin (SIg) and positivity for B-cell antigens (CD19, CD20 and CD22). HLA-DR and FMC7 are also positive. CD5 is variable; CD10 and CD103 are negative although in 6% of cases CD103 may be positive. CD23 is negative to weak positive. CD11c and CD25 may be either positive or negative. The absence of CD5 is useful in excluding chronic lymphatic leukaemia; the absence of CD103 is useful in excluding hairy cell leukaemia while the absence of CD10 is useful in excluding follicular lymphoma.

Whilst immunophenotyping is helpful in the diagnosis of SMZL, no one marker is specific in distinguishing it from other B-cell lymphomas/leukaemias. Once again morphology plays an important role in making the correct diagnosis.

The most commonly seen cytogenetic abnormalities in SMZL are loss of chromosome 7q 21-32 occurring in 40% of cases; t(11;14)(q13;q32) occurring in 5-10% of cases as well as trisomy 3 occurring in about 20% of cases.

Clinically, SMZL is recognised as being in the category of an indolent lymphoma. Response to chemotherapy is poor compared to other chronic lymphoid leukaemias/lymphomas. Patients with SMZL typically have a good response to splenectomy with long term survival.