YO19 - A case of CLL/SLL with transdifferentiation to dendritic cell tumor and possibly a hybrid lymphodendritic cell neoplasm:The missing link?

Case summary

Recent studies have shown evidence of cross-lineage transdifferentiation of B-cell lymphomas, such as low-grade FL and CLL/SLL,to histiocytic and dendritic cell sarcomas, but the clonal relationship between the 2 neoplasms is still unclear. Here, we report the morphologic, molecular and cytogenetic analysis of a unique case of CLL/SLL associated with indeterminate dendritic cell tumor and possibly a hybrid lymphodendritic cell neoplasm , using immunohistochemistry, electron microscopy, in situ hybridization and FISH.A 48-year-old Chinese female presented with left upper neck swelling. Blood examination revealed lymphocytosis.Microscopic examinations showed the lymph node has effaced architecture, and has a very complicated, variegated appearance with three distinct components. The first component contained small lymphocytes, prolymphocytes and paraimmunoblasts, showing typical CLL/SLL immunophenotype, with ZAP-70 positive and EBV negative. The second component contained nodular aggregates of large pink cells with abundant eosinophilic cytoplasm and deeply grooved nuclei, showing immunophenotype of indeterminate dendritic cell tumor and EBV positive. The third component had intermediate morphologic features between lymphoid cells and dendritic cells characteristics, a bit reminiscent of anaplastic large cell lymphoma, but expressed some B cell markers PAX5 and OCT2, as well as dendritic/histiocytic markers CD1a, CD68, Fascin, and Lysozyme, and was diffusely EBV positive. Electron microscopy revealed the cells in the third component had short and thick bulges like dendritic cell. FISH analysis using CLL probes showed identical deletion 17p13.1, deletion 11q22.3, and deletion 13q14.3 in all 3 components. Sharing of CD5 and OCT2 expression and identical cytogenetic abnormality in all 3 components suggest a common clonal origin for the three components.Our study provides evidence for transdifferentiation of CLL/SLL to dendritic cell tumor possibly via the intermediate linklymplymphodendritic cell neoplasm, and suggests that EBV may play a role in this phenomenon.

Clinical trial identification

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