Transformation of Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma to Histiocytic/Dendritic Cell Sarcoma.

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) transforming into a more aggressive lymphoma (i.e., Richter syndrome) is well documented in the literature. In recent years, transdifferentiation of CLL/SLL to histiocytic/dendritic/Langerhans cell sarcomas has also been reported. We hereby describe a case of a 55-year-old female who was incidentally diagnosed with CLL after presenting to the hospital for symptoms of undiagnosed rheumatoid arthritis. At the time of presentation, CLL was stage 1, and the patient was placed on observation. Eight years after being diagnosed with CLL, and after several treatment modalities for her rheumatoid arthritis, the patient re-presented with progression of adenopathy, intermittent fevers, 5-pound weight loss, and worsening respiratory status requiring airway management. Computed tomography (CT) imaging revealed a soft tissue mass in the nasopharynx, lingual tonsillar hypertrophy with airway compromise, and bulky cervical, supraclavicular, and axillary lymphadenopathy. A biopsy of an enlarged cervical lymph node yielded a diagnosis of histiocytic/dendritic cell sarcoma favoring interdigitating dendritic cell sarcoma, likely representing transdifferentiation from CLL/SLL, of which there are no standard of care treatment guidelines. The patient was treated with ifosfamide, carboplatin, and etoposide (ICE) for three cycles, followed by rituximab, etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (R-EPOCH) in combination with zanubrutinib. She then underwent haploidentical hematopoietic stem cell transplantation. At the time of the making of this manuscript, the patient was 45 days post-transplant without any notable complications.