Isolated Pancreatic Myeloid Sarcoma Associated with t(8;21)/RUNX1-RUNX1T1 Rearrangement

Abstract

No valid treatment for isolated myeloid sarcoma (IMS) has yet been established, and no thorough genetic examinations have been performed because of its low incidence and unique manner of development. We herein report a 34-year-old man with pancreatic IMS with t(8;21)/RUNX1-RUNX1T1 rearrangement. He was treated with high-dose cytarabine followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT). This is the first report of pancreatic IMS with t(8;21). Positron emission tomography/computed tomography and genetic study are useful for the diagnosis, and allo-HSCT achieved complete remission in this patient.

Keywords: isolated myeloid sarcoma; pancreas; t(8;21).

Figure 1.

Bulky tumor of the pancreas found with enhanced-contrast computed tomography (CT) and laparoscopy. (A) Contrast-enhanced CT revealed ischemic bulky tumor of the pancreas (arrows). (B) A laparoscopic examination revealed a pancreatic tumor and thick omentum (arrows). (C) Turbid ascites (arrows).

Figure 2.

Cytology and histology of tumor cells. A biopsy of the pancreatic tumor revealed myeloid sarcoma. May-Giemsa staining revealed that the tumor cells with blue-gray cytoplasm were leukemic blast-like cells. An immunohistochemical analysis showed that the tumor cells were negative for lymphoid and epithelial markers, CD3, CD7, CD20, TdT or cytokeratin AE1/AE3, and positive for myeloid and monocyte antigens, CD33, CD34, CD68/Kp-1 and MPO. HE: Hematoxylin and Eosin staining, MPO: myeloperoxidase, TdT: terminal deoxynucleotidyl transferase. Magnification: all photomicrographs ×400

Figure 3.

A genetic analysis with RT-PCR. RUNX1-RUNX1T1 fusion mRNA was detected by reverse transcription polymerase chain reaction in tumor cells and BM cells at the diagnosis. The Kasumi-1 acute myeloid leukemia cell line was utilized as a positive control representing cells with the RUNX1-RUNX1T1 gene. The K562 and Nalm6 cell lines were negative controls. The fusion mRNA-specific PCR product length was 395 base pairs (pointed by the white arrow). Larger sized bands are non-specific. BM: bone marrow mononuclear cell, K1: Kasumi1, K56: K562, M: marker, N6: Nalm6, T: tumor cell

Figure 4.

Clinical course of the case of pancreatic isolated myeloid sarcoma. Following chemotherapy, the bulky pancreatic tumor shrank and showed reduced uptake signals on positron emission tomography/computed tomography (PET/CT). WT1 mRNA was reduced to 10^-1 copies after the consolidative therapies. Allogeneic hematopoietic stem cell transplantation was performed. The conditioning regimen was busulfan and cyclophosphamide. At 18 months after the diagnosis, the WT1 mRNA count dropped below 50 copies/μgRNA (lower limit of normal). RUNX1-RUNX1T1 mRNA RT-PCR was performed qualitatively. The black bars in the pictures of PET/CT are used to cover identifying patient information. Allo-HSCT: allogeneic hematopoietic stem cell transplantation, Bu/CY: busulfan and cyclophosphamide conditioning, C1-3: consolidation therapy cycles 1-3, HDAC: high dose cytarabine regimen, IDR/AraC: idarubicin and cytarabine regimen, RIT: remission induction therapy, RUNX1-RU NX1T1 mRNA: results of the qualitative RT-PCR for RUNX1-RUNX1T1 mRNA, WT1: Wilms’ tumor 1 mRNA