Chapter e21

The most common lymphoid malignancies are discussed in Chap. 110, myeloid leukemias in Chap. 109, myelodysplastic syndromes in Chap. 107, and myeloproliferative syndromes in Chap. 108. This chapter will focus on the more unusual forms of hematologicmalignancy. The diseases discussed here are listed in Table e21-1. Each of these entities accounts for less than 1% of hematologic neoplasms.

Table e21-1 Unusual Lymphoid and Myeloid Malignancies

Precursor B cell and precursor T cell neoplasms are discussed in Chap. 110. All the lymphoid tumors discussed here are mature B cell or T cell, natural killer (NK) cell neoplasms.

Mature B Cell Neoplasms

B Cell Prolymphocytic Leukemia (B-PLL)

This is a malignancy of medium-sized (about twice the size of a normal small lymphocyte), round lymphocytes with a prominent nucleolus and light blue cytoplasm on Wright's stain. It dominantly affects the blood, bone marrow, and spleen and usually does not cause adenopathy. The median age of affected patients is 70 years and men are more often affected than women (male/female ratio is 1.6). This entity is distinct from chronic lymphoid leukemia (CLL) and does not develop as a consequence of that disease.

Clinical presentation is generally from symptoms of splenomegaly or incidental detection of an elevated WBC count. The clinical course can be rapid. The cells express surface IgM (with or without IgD) and typical B cell markers (CD19, CD20, CD22). CD23 is absent and about one-third of cases express CD5. The CD5 expression along with the presence of the t(11;14) translocation in 20% of cases leads to confusion in distinguishing B-PLL from the leukemic form of mantle cell lymphoma. No reliable criteria for the distinction have emerged. About half of patients have mutation or loss of p53 and deletions have been noted in 11q23 and 13q14. Nucleoside analogues like fludarabine and cladribine and combination chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone, or CHOP) have produced responses. CHOP plus rituximab may be more effective than CHOP ...

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