Society for Hematopathology/ European Association for Haematopathology Case 211 Rachel Ochs, MD Adam Bagg, MD Hospital of the University of Pennsylvania Philadelphia, PA

Clinical History - Presentation 41-year-old man, presented with pancytopenia and disseminated intravascular coagulation in June 2002 Diagnosed with morphologically classical hypergranular t(15;17)(q24;q12)–positive APL Metaphase cytogenetic studies in the bone marrow were normal, but the PML-RARA fusion was detected by both FISH and qualitative reverse-transcription polymerase chain reaction (RT-PCR)

Clinical History - Treatment All-trans-retinoic acid (ATRA) therapy was initiated – pt developed differentiation syndrome Induction therapy with cytarabine, daunorubicin, and ATRA – subsequent attainment of molecular and hematologic remission Consolidation chemotherapy: idarubicin alternating with mitoxantrone

Disease course 2004: Relapse, molecular only in bone marrow – Treatment: Arsenic followed by autologous stem-cell transplant 2005: Relapse, peripheral blood and CNS involvement – Treatment: ATRA, intrathecal cytarabine, and CNS radiation – After the attainment of a second remission (by RT-PCR), he underwent nonmyeloablative 9/10 allele-matched unrelated- donor stem-cell transplantation in March (December): Relapse, bone marrow (morphologically evident) – Treatment: ATRA and donor lymphocyte infusion – Molecular studies on bone marrow showed full engraftment for 15 months, as well as negativity for PML-RARA

Disease course (cont.) 2008: Presented with bowel obstruction and ascites, found to have large small bowel mass – Tandem peripheral blood engraftment studies showed 100% donor DNA, and bone marrow examination showed no morphologic or cytogenetic evidence of disease – RT-PCR (ascites fluid and peripheral blood) was positive for a PML-RARA fusion – Small bowel mass was resected

Extramedullary APL, small bowel (5X)

Extramedullary APL, small bowel (40X)

APL, ascites fluid

Flow cytometry, ascites fluid

Gel electrophoresis following analysis with PML-bcr3 primer, lane 5, arrowed Lane 1 = size markers; lane 10 = positive control for PML-bcr3; lane 11 = positive control for PML-bcr1; lane 8 = non-specific band; all other lanes = negative specimens and negative controls

Proposed Diagnosis Acute promyelocytic leukemia, isolated extramedullary relapse (small bowel) without bone marrow involvement Consensus Diagnosis Acute promyelocytic leukemia, with t(15;17)(q24.1;q21.2), PML-RARA, involving only small intestine (myeloid sarcoma) at relapse

Extramedullary relapse: Targeted therapy Extramedullary relapse (EMR) rates may be increasing in the era of targeted therapy Possible causes: – Patients are surviving longer – Sanctuary sites in which ATRA and arsenic do not reach therapeutic concentrations? – ATRA and arsenic increase the expression of adhesion molecules in leukemic cells (eg, CD11b, CD11c, CD18, and CD56), which could allow those cells to access numerous different tissues – ATRA may induce expression of multiple CC chemokines, which may result in increased chemotaxis into tissues – Differentiation syndrome allows leukemic cells to infiltrate different organ tissues (known risk factor for EMR)

Extramedullary relapse: Bone marrow transplant Suggested that graft vs. leukemia effect is more potent in bone marrow, and may help suppress bone marrow relapse more than extramedullary relapse in patients with chronic GVHD CD8-positive T cells and natural killer cells are present in higher numbers in BM than in EM tissues Patients with haplo-stem cell transplant may have higher rates of extramedullary relapse (GVL effect elicited by HLA disparity occurs preferentially in bone marrow?)

Follow-up Arsenic attempted as salvage therapy, however there was disease progression and the patient expired shortly (<1 month) after presentation with granulocytic sarcoma