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Donor cell leukemia (DCL) is a rare complication of transplantation. In 1971, Fialkow reported the case of a female patient with ALL who relapsed after a transplant from her brother. Cytogenetics showed only donor derived XY metaphases. Sporadic cases of DCL have since been reported, however, the precise incidence remains unclear. An EBMT review of 10489 allogeneic transplants found an incidence of ~0.1%.
Case Report
A 41-year-old-man was admitted 567 days after a double unrelated blood cord transplantation (UBCT) for B-ALL. He received reduced-intensity conditioning prior to his UBCT with cyclophosphamide 50 mg/kg, fludarabine 200 mg/m2, and 200 cGy TBI (Cy/Flu/TBI). GVHD prophylaxis included CSA and MMF. Post-transplant, bone marrow (BM) and peripheral blood (PB) chimerism was 100% donor.
On day+515 post-transplant he was thrombocytopenic with 8% blasts. A BM biopsy revealed a donor derived AML, with 22% blasts. BM chimerism remained 100% donor. He received decitabine at 20mg/m2 for 10 days. Post- treatment BM biopsy was negative for AML.
On day+567, he was admitted with fever, pleuritic chest pain and tachycardia. EKG demonstrated T-wave inversions in V3-V5. Both troponin (1.8 ng/ml) and BNP (805 pg/ml) were elevated. Chest CT revealed a circumferential pericardial and nodular soft tissue densities posterior to the heart and he ultimately underwent a pericardectomy.
The pericardial pathology showed myeloid sarcoma. The tumor cells were CD43+, MPO focal+, CD34 focal+, CD117 focal+, CD68 weak+, CD163 focal+, PAX5-, CD56-, TdT-, CD79a focal weak+ by immunohistochemistry. The chimerism revealed that the lesion was entirely donor derived. A BM biopsy showed no evidence of AML with normal hematopoiesis and full donor chimerism. Thus, cardiac myeloid sarcoma represented an isolated site of disease.
Unfortunately, the patient continued to deteriorate and expired on day+579.
Discussion
Within DCL, isolated donor derived granulocytic sarcoma, as in our patient, is an extremely rare and challenging diagnosis. Reactive donor leukocytes can infiltrate a host derived granulocytic sarcoma making it difficult to distinguish relapse from a DCL.
Given the comparatively recent introduction of UCBT, fewer cases of cord blood associated DCL leukemia have been reported in the literature when compared with PBSCT or BMT. Some interesting trends have emerged. AML is the most common type of UCBT DCL. There is a shorter interval to the development of DCL in UCBT (median of 14.5 months) compared to BMT or PBSCT (36 months). Abnormal karyotypes, particularly monosomy 7, are more common in UCBT DCL. Perhaps, UCB is uniquely sensitive to leukemogenic effects of conditioning. Given the predominance of AML DCL in UCBT, more cases of donor myeloid sarcoma, may emerge. Improved molecular testing will allow precise detection and avoid mistakenly categorizing DCL as relapsed disease.