Clinical history: A 58-year-old male with history of chronic lymphocytic leukemia for 10 years, presents with enlarged left neck node. An excisional biopsy was performed.
Microscopic Description: Sections show sheets of lymphoid tissue infiltrating into the surrounding fibrous and adipose tissue. Representative areas are shown in figure 2.1 and 2.2. In a small part (area 1), the predominant cells are normal appearing small lymphocytes that have a round nucleus with clumped chromatin and occasionally discernible nucleoli. A similar population of small lymphocytes is also seen in the larger part of the tissue (area 2), which in addition shows a second population of much larger cells with blastoid morphology having round to oval nuclei, dispersed chromatin and central to paracentral, large, eosinophilic nucleolus. In some areas these larger cells are the dominant cell type (area 3). This larger part of the tissue also shows a high mitotic rate and a large number of tingible body macrophages. There is no definite follicle formation. Typical Reed-Sternberg cells are not seen.
Immunophenotyping shows all of the neoplastic cells to be equally positive for CD20, CD5, CD23, CD43 and bcl2 (Fig 2.3-2. ); but negative for CD3 and CD10. There is also no staining for TdT, IgD, cyclin D and p53. The proliferative index by Ki67 (Fig 2.5) is focally low (area 1, parts showing mostly small lymphocytes), but in the larger part of the lesion it is >50%.