Case 4
A 63-year-old male on tacrolimus and mycophenolate mofetil (MMF) for prior renal transplant was admitted for a several-week history of episodic fevers. His prior workup, including cultures and serologies for viral infections, was negative. Pertinent labs at admission: WBC 2.1 x 109/L, Hb 10.2 gm/dL, platelets 60 x 109/L, total bilirubin 0.9 mg/dL, LDH 554 IU/L, ESR 11 mm/hr. Peripheral blood smear showed moderate anisocytosis and normal WBC and platelet morphology. Bone marrow biopsy showed trilineage hematopoiesis with occasional large atypical lymphoid cells in small vessels. Cells were positive for CD20, CD79s, and CD5, and mostly negative for BCL-2, BCL-6, and CD10. Cytogenetic studies showed abnormal clones with structural rearrangements of chromosomes 3, 5, 9, 10, and 14 along with loss of 6q. Follow-up random skin biopsies showed rare, atypical intravascular B cells positive for CD20. EBER was negative. CT neck, chest, abdomen, and pelvis were negative for lymphadenopathy. CSF was negative for malignant cells. He received six cycles of R-CHOP with intrathecal methotrexate with the recovery of counts. MMF was discontinued at the time of diagnosis. Follow-up PET/CT did not show any evidence of disease. Post-treatment bone marrow biopsy was negative for any morphological or immunophenotypic evidence of lymphoma. The patient continues to be in remission on follow-up.