Graft-Versus-Leukemia Effect in the Management of Isolated Pancreatic Granulocytic Sarcoma Following Allogeneic Stem Cell Transplantation

Granulocytic sarcoma (GS), also known as chloroma, is a rare extramedullary tumor composed of immature myeloid cells, most often seen in association with acute myeloid leukemia (AML). Isolated GS without bone marrow involvement is extremely uncommon, and fewer than 15 cases of isolated pancreatic GS have been reported in the literature. It is frequently misdiagnosed due to its morphological resemblance to lymphoid malignancies. We present the case of a 19-year-old male who developed obstructive jaundice and was found to have a pancreatic mass initially interpreted as a peripheral T-cell lymphoma. Further biopsy and immunohistochemical analysis confirmed the diagnosis of GS, with strong positivity for myeloperoxidase, lysozyme, and CD68. Bone marrow evaluation and cytogenetic analysis were normal, confirming isolated disease. The patient was treated with AML-based chemotherapy, which resulted in only a minimal reduction in tumor size. Nine months later, he underwent allogeneic stem cell transplantation (allo-SCT) from an HLA-identical sibling. Follow-up imaging at four months post-transplant revealed a dramatic reduction of over 90% in the mass size. At eight months, the patient remained in complete clinical and hematologic remission. This case highlights the diagnostic and therapeutic challenges of isolated GS in an atypical site and provides evidence for a potential graft-versus-leukemia effect in extramedullary disease. The post-transplant tumor regression, despite limited chemotherapy response, underscores the significance of immune-mediated control and suggests a possible role for allo-SCT even in preleukemic GS.